Category Archive Nutrition Care

How Much Vegetables I Have Needed In A Day

How Much Vegetables I have Needed In A Day/Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems, leaves, roots, and seeds. An alternate definition of the term is applied somewhat arbitrarily, often by culinary and cultural tradition. It may exclude foods derived from some plants that are fruits, flowers, nuts, and cereal grains, but include savory fruits such as tomatoes and courgettes, flowers such as broccoli, and seeds such as pulses.

A diet rich in vegetables and fruits can lower blood pressure, reduce the risk of heart disease and stroke, prevent some types of cancer, lower risk of eye and digestive problems, and have a positive effect upon blood sugar, which can help keep appetite in check. Eating non-starchy vegetables and fruits like apples, pears, and green leafy vegetables may even promote weight loss. Their low glycemic loads prevent blood sugar spikes that can increase hunger.

At least nine different families of fruits and vegetables exist, each with potentially hundreds of different plant compounds that are beneficial to health. Eat a variety of types and colors of produce in order to give your body the mix of nutrients it needs. This not only ensures greater diversity of beneficial plant chemicals but also creates eye-appealing meals.

These are general recommendations by age. Find the right amount for you by getting your

Daily Recommendation*
Toddlers 12 to 23 months ⅔ to 1 cup
Children 2-4 yrs 1 to 2 cups
5-8 yrs 1½ to 2½ cups
Girls 9-13 yrs 1½ to 3 cups
14-18 yrs 2½ to 3 cups
Boys 9-13 yrs 2 to 3½ cups
14-18 yrs 2½ to 4 cups
Women 19-30 yrs 2½ to 3 cups
31-59 yrs 2 to 3 cups
60+ yrs 2 to 3 cups
Men 19-30 yrs 3 to 4 cups
31-59 yrs 3 to 4 cups
60+ yrs 2½ to 3½ cups

The amount that counts as 1 cup of vegetables

The amount that counts as 1 cup of vegetables
Dark-Green Vegetables Broccoli 1 cup, chopped or florets, fresh or frozen
Bitter melon leaves, chrysanthemum leaves, escarole, lambs quarters, nettles, poke greens, taro leaves, turnip greens 1 cup, cooked
Amaranth leaves, beet greens, bok choy, broccoli raab (rapini), chard, collards (collard greens), cress, dandelion greens, kale, mustard greens, spinach, Swiss chard, watercress 1 cup, cooked

2 cups, fresh

Raw leafy greens: Arugula (rocket), basil, cilantro,  dark green leafy lettuce, endive, escarole, mixed greens, mesclun, romaine 2 cups, fresh
Red and Orange Vegetables Carrots 2 medium carrots

1 cup, sliced or chopped, fresh, cooked, or frozen

1 cup baby carrots

Pimento/Pimiento 3 whole

1 cup

Pumpkin, calabaza 1 cup, mashed, cooked
Red and orange bell peppers 1 large bell pepper

1 cup, chopped, fresh, or cooked

Red chili peppers ¾ cup
Sweet potato 1 large sweet potato, baked

1 cup, sliced or mashed, cooked

Tomatoes 1 large tomato

2 small tomatoes

1 cup, chopped or sliced, fresh, canned, or cooked

100% vegetable juice 1 cup
Winter squash (acorn, butternut, hubbard, kabocha) 1 cup, cubed, cooked
Beans, Peas, and Lentils Dry beans and peas and lentils (such as bayo, black, brown, fava, garbanzo, kidney, lima, mung, navy, pigeon, pink, pinto, soy, or white beans, or black-eyed peas (cow peas) or split peas, and red, brown, and green lentils) 1 cup, whole or mashed, cooked
Starchy Vegetables Breadfruit 1 ½ cups, cooked
Cassava ¾ cup, cooked
Corn, yellow or white 1 large ear of corn

1 cup corn kernels, fresh or frozen

Green peas 1 cup fresh or frozen
Hominy 1 cup, cooked
Plantains ¾ cup, cooked
White potatoes 1 medium white potato, boiled or baked

1 cup, diced, mashed, fresh or frozen

Other Vegetables Avocado 1 avocado
Bamboo shoots 1 cup
Bean sprouts 1 cup, cooked
Cabbage, green, red, napa, savoy 1 cup, chopped or shredded raw or cooked
Cactus pads (nopales) 5 pads

1 cup sliced

Cauliflower 1 cup, pieces or florets raw or cooked, fresh or frozen
Celery 1 cup, diced or sliced, raw or cooked

2 large stalks (11″ to 12″ long)

Cucumbers 1 cup, raw, sliced or chopped
Green or wax beans 1 cup, cooked
Green bell peppers 1 large bell pepper

1 cup, chopped, raw or cooked, fresh or frozen

Lettuce, iceberg or head 2 cups, raw, shredded or chopped
Mushrooms 1 cup, raw or cooked
Okra 1 cup, cooked
Onions 1 cup, chopped, raw or cooked
Summer squash or zucchini 1 cup, cooked, sliced or diced

Health Benefits

All food and beverage choices matter – focus on variety, amount, and nutrition.

  • As part of an overall healthy diet, eating foods such as vegetables that are lower in calories per cup instead of some other higher-calorie food may be useful in helping to lower calorie intake.
  • Eating a diet rich in vegetables and fruits as part of an overall healthy diet may reduce risk for heart disease, including heart attack and stroke.
  • Eating a diet rich in some vegetables and fruits as part of an overall healthy diet may protect against certain types of cancers.
  • Adding vegetables can help increase intake of fiber and potassium, which are important nutrients that many Americans do not get enough of in their diet.

Vegetables are well-known for being good for your health. Most vegetables are low in calories but high in vitamins, minerals and fiber. However, some vegetables stand out from the rest with additional proven health benefits, such as the ability to fight inflammation or reduce the risk of disease.

Which Kind Of Vegetables Are Best According To My Age

1. Spinach

  • This leafy green tops the chart as one of the healthiest vegetables, thanks to its impressive nutrient profile.
  • One cup (30 grams) of raw spinach provides 56% of your daily vitamin A needs plus your entire daily vitamin K requirement — all for just 7 calories (rx).
  • Spinach also boasts a lot of antioxidants, which can help reduce the risk of chronic disease.
  • One study found that dark green leafy vegetables like spinach are high in beta-carotene and lutein, two types of antioxidants that have been associated with a decreased risk of cancer (rx).
  • In addition, a 2015 study found that spinach consumption may be beneficial for heart health, as it may lower blood pressure (rx).

SUMMARY:Spinach is rich in antioxidants that may reduce the risk of chronic disease, as it may reduce risk factors such as high blood pressure.

2. Carrots

  • Carrots are packed with vitamin A, providing 428% of the daily recommended value in just one cup (128 grams) (rx).
  • They contain beta-carotene, an antioxidant that gives carrots their vibrant orange color and could help in cancer prevention (rx).
  • In fact, one study revealed that for each serving of carrots per week, participants’ risk of prostate cancer decreased by 5% (rx).
  • Another study showed that eating carrots may reduce the risk of lung cancer in smokers as well. Compared to those who ate carrots at least once a week, smokers who did not eat carrots had a three times greater risk of developing lung cancer (rx).
  • Carrots are also high in vitamin C, vitamin K and potassium (rx).

SUMMARY:Carrots are especially high in beta-carotene, which can turn into vitamin A in the body. Their high antioxidant content may help reduce the risk of lung and prostate cancer.

3. Broccoli

  • Broccoli belongs to the cruciferous family of vegetables.
  • It is rich in a sulfur-containing plant compound known as glucosinolate, as well as sulforaphane, a by-product of glucosinolate (rx).
  • Sulforaphane is significant in that it has been shown to have a protective effect against cancer.
  • In one animal study, sulforaphane was able to reduce the size and number of breast cancer cells while also blocking tumor growth in mice (rx).
  • Eating broccoli may help prevent other types of chronic disease, too.
  • A 2010 animal study found that consuming broccoli sprouts could protect the heart from disease-causing oxidative stress by significantly lower levels of oxidants (rx).
  • In addition to its ability to prevent disease, broccoli is also loaded with nutrients.
  • A cup (91 grams) of raw broccoli provides 116% of your daily vitamin K needs, 135% of the daily vitamin C requirement and a good amount of folate, manganese and potassium (rx).

SUMMARY:Broccoli is a cruciferous vegetable that contains sulforaphane, a compound that may prevent cancer growth. Eating broccoli may also help reduce the risk of chronic disease by protecting against oxidative stress.

4. Garlic

  • Garlic has a long history of use as a medicinal plant, with roots tracing all the way back to ancient China and Egypt (rx).
  • The main active compound in garlic is allicin, a plant compound that is largely responsible for garlic’s variety of health benefits (rx).
  • Several studies have shown that garlic can regulate blood sugar as well as promote heart health.
  • In one animal study, diabetic rats were given either garlic oil or diallyl trisulfide, a component of garlic. Both garlic compounds caused a decrease in blood sugar and improved insulin sensitivity (rx).
  • Another study fed garlic to participants both with and without heart disease. Results showed that garlic was able to decrease total blood cholesterol, triglycerides, and LDL cholesterol while increasing HDL cholesterol in both groups (rx).
  • Garlic may be useful in the prevention of cancer as well. One test-tube study demonstrated that allicin induced cell death in human liver cancer cells (rx).
  • However, further research is needed to better understand the potential anti-cancer effects of garlic.

SUMMARY:Studies show that garlic may help lower blood triglyceride levels. Some studies have also found that it could decrease blood sugar levels and may have an anti-cancer effect, although more research is needed.

5. Brussels Sprouts

  • Like broccoli, Brussels sprouts are a member of the cruciferous family of vegetables and contain the same health-promoting plant compounds.
  • Brussels sprouts also contain kaempferol, an antioxidant that may be particularly effective in preventing damage to cells (rx).
  • One animal study found that kaempferol protected against free radicals, which cause oxidative damage to cells and can contribute to chronic disease (rx).
  • Brussels sprout consumption can help enhance detoxification as well.
  • One study showed that eating Brussels sprouts led to a 15–30% increase in some of the specific enzymes that control detoxification, which could decrease the risk of colorectal cancer (rx).
  • Additionally, Brussels sprouts are very nutrient-dense. Each serving provides a good amount of many vitamins and minerals, including vitamin K, vitamin A, vitamin C, folate, manganese and potassium (rx).

SUMMARY:Brussels sprouts contain an antioxidant called kaempferol, which may protect against oxidative damage to cells and prevent chronic disease. They may also help enhance detoxification in the body.

6. Kale

  • Like other leafy greens, kale is well-known for its health-promoting qualities, including its nutrient density and antioxidant content.
  • A cup (67 grams) of raw kale contains plenty of B vitamins, potassium, calcium and copper.
  • It also fulfills your entire daily requirement for vitamins A, C, and K (rx).
  • Due to its high amount of antioxidants, kale may also be beneficial in promoting heart health.
  • In a 2008 study, 32 men with high cholesterol drank 150 ml of kale juice daily for 12 weeks. By the end of the study, HDL cholesterol increased by 27%, LDL cholesterol decreased by 10% and antioxidant activity was increased (rx).
  • Another study showed that drinking kale juice can decrease blood pressure and may be beneficial in reducing both blood cholesterol and blood sugar (rx).

SUMMARY:Kale is high in vitamins A, C and K as well as antioxidants. Studies show that drinking kale juice could reduce blood pressure and LDL cholesterol while increasing HDL cholesterol.

7. Green Peas

  • Peas are considered starchy vegetables. This means they have a higher amount of carbs and calories than non-starchy vegetables and may impact blood sugar levels when eaten in large amounts.
  • Nevertheless, green peas are incredibly nutritious.
  • One cup (160 grams) of cooked green peas contains 9 grams of fiber, 9 grams of protein and vitamins A, C and K, riboflavin, thiamin, niacin and folate (rx).
  • Because they are high in fiber, peas support digestive health by enhancing the beneficial bacteria in your gut and promoting regular bowel movements (rx).
  • Moreover, peas are rich in saponins, a group of plant compounds known for their anti-cancer effects (rx).
  • Research shows that saponins may help fight cancer by reducing tumor growth and inducing cell death in cancer cells (rx).

SUMMARY:Green peas contain a good amount of fiber, which helps support digestive health. They also contain plant compounds called saponins, which may have anti-cancer effects.

8. Swiss Chard

  • Swiss chard is low in calories but high in many essential vitamins and minerals.
  • One cup (36 grams) contains just 7 calories yet 1 gram of fiber, 1 gram of protein and lots of vitamins A, C and K, manganese and magnesium (rx).
  • Swiss chard is especially known for its potential to prevent damage caused by diabetes mellitus.
  • In one animal study, chard extract was found to reverse the effects of diabetes by decreasing blood sugar levels and preventing cell damage from disease-causing free radicals (rx).
  • Other animal studies have shown that the antioxidant content of chard extract can protect the liver and kidneys from the negative effects of diabetes (rx, rx).

SUMMARY:Some animal studies show that Swiss chard could protect against the negative effects of diabetes and may decrease blood sugar levels.

9. Ginger

  • Ginger root is used as a spice in everything from vegetable dishes to desserts.
  • Historically, ginger has also been used as a natural remedy for motion sickness (rx).
  • Several studies have confirmed the beneficial effects of ginger on nausea. In a review comprised of 12 studies and nearly 1,300 pregnant women, ginger significantly reduced nausea compared to a placebo (rx).
  • Ginger also contains potent anti-inflammatory properties, which can be helpful in treating inflammation-related disorders like arthritis, lupus or gout (rx).
  • In one study, participants with osteoarthritis who were treated with a concentrated ginger extract experienced reduced knee pain and relief from other symptoms (rx).
  • Further research suggests that ginger could aid in the treatment of diabetes as well.
  • A 2015 study looked at the effects of ginger supplements on diabetes. After 12 weeks, ginger was found to be effective in decreasing blood sugar levels (rx).

SUMMARY:Studies show that ginger could reduce nausea and alleviate inflammation. Ginger supplements may also help decrease blood sugar.

10. Asparagus

  • This spring vegetable is rich in several vitamins and minerals, making it an excellent addition to any diet.
  • Just half a cup (90 grams) of asparagus provides one-third of your daily folate needs.
  • This amount also provides plenty of selenium, vitamin K, thiamin, and riboflavin (rx).
  • Getting enough folate from sources like asparagus can offer protection from disease and can prevent neural tube birth defects during pregnancy (rx, rx).
  • Some test-tube studies also show that asparagus may benefit the liver by supporting its metabolic function and protecting it against toxicity (rx).

SUMMARY:Asparagus is especially high in folate, which may help prevent neural tube birth defects. Test-tube studies have also found that asparagus can support liver function and reduce the risk of toxicity.

11. Red Cabbage

  • This vegetable belongs to the cruciferous family of vegetables and, much like its relatives, is brimming with antioxidants and health-promoting properties.
  • One cup (89 grams) of raw red cabbage contains 2 grams of fiber as well as 85% of the daily vitamin C requirement (rx).
  • Red cabbage is also rich in anthocyanins, a group of plant compounds that contribute to its distinct color as well as a whole host of health benefits.
  • In a 2012 animal study, rats were fed a diet designed to increase cholesterol levels and increase plaque buildup in the arteries. The rats were then given red cabbage extract.
  • The study found that red cabbage extract was able to prevent increases in blood cholesterol levels and protect against damage to the heart and liver (rx).
  • These results were supported by another animal study in 2014 showing that red cabbage could reduce inflammation and prevent liver damage in rats fed a high-cholesterol diet (rx).

SUMMARY:Red cabbage contains a good amount of fiber, vitamin C and anthocyanins. Certain studies show that it may decrease blood cholesterol levels, reduce inflammation and lower the risk of heart and liver damage.

12. Sweet Potatoes

  • Classified as a root vegetable, sweet potatoes stand out for their vibrant orange color, sweet taste and impressive health benefits.
  • One medium sweet potato contains 4 grams of fiber, 2 grams of protein and a good amount of vitamin C, vitamin B6, potassium and manganese (rx).
  • It’s also high in a form of vitamin A called beta-carotene. In fact, one sweet potato fulfills 438% of your daily vitamin A needs (rx).
  • Beta-carotene consumption has been linked to a significant decrease in the risk of certain types of cancer, including lung and breast cancer (rx, rx).
  • Specific types of sweet potatoes may also contain additional benefits. For example, Caiapo is a type of white sweet potato that may have an anti-diabetic effect.
  • In one study, people with diabetes were given 4 grams of Caiapo daily over 12 weeks, leading to a reduction in both blood sugar and blood cholesterol levels (rx).

SUMMARY:Sweet potatoes are high in beta-carotene, which may decrease the risk of some types of cancer. White sweet potatoes could also help reduce blood cholesterol and blood sugar levels.

13. Collard Greens

  • Collard greens are a very nutrient-rich vegetable.
  • One cup (190 grams) of cooked collard greens contains 5 grams of fiber, 4 grams of protein and 27% of your daily calcium needs (rx).
  • In fact, collard greens are one of the best plant sources of calcium available, along with other leafy greens, broccoli and soybeans.
  • Adequate calcium intake from plant sources can promote bone health and has been shown to decrease the risk of osteoporosis (rx).
  • Collard greens are also high in antioxidants and could even reduce your risk of developing certain diseases.
  • One study found that eating more than one serving of collard greens per week was associated with a 57% decreased risk of glaucoma, an eye condition that can lead to blindness (rx).
  • Another study showed that a high intake of vegetables in the Brassica family, which includes collard greens, may decrease the risk of prostate cancer (rx).

SUMMARY:Collard greens are high in calcium, which could reduce the risk of osteoporosis. The regular intake of collard greens has also been associated with a reduced risk of glaucoma and prostate cancer.

14. Kohlrabi

  • Also known as the turnip cabbage or German turnip, kohlrabi is a vegetable related to the cabbage that can be eaten raw or cooked.
  • Raw kohlrabi is high in fiber, providing 5 grams in each cup (135 grams). It’s also full of vitamin C, providing 140% of the daily value per cup (rx).
  • Studies have shown that the antioxidant content of kohlrabi makes it a powerful tool against inflammation and diabetes (rx).
  • In one animal study, kohlrabi extract was able to decrease blood sugar levels by 64% within just seven days of treatment (rx).
  • Though there are different types of kohlrabi available, studies show that red kohlrabi has nearly twice the amount of phenolic antioxidants and displays stronger anti-diabetic and anti-inflammatory effects (rx).

SUMMARY:Kohlrabi is rich in both fiber and vitamin C. Animal studies show that kohlrabi could potentially cause a reduction in blood sugar.

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Which Kind Of Vegetables Are Best According To My Age

Which Kind Of Vegetables Are Best According To My Age/Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems, leaves, roots, and seeds. An alternate definition of the term is applied somewhat arbitrarily, often by culinary and cultural tradition. It may exclude foods derived from some plants that are fruits, flowers, nuts, and cereal grains, but include savory fruits such as tomatoes and courgettes, flowers such as broccoli, and seeds such as pulses.

A diet rich in vegetables and fruits can lower blood pressure, reduce the risk of heart disease and stroke, prevent some types of cancer, lower risk of eye and digestive problems, and have a positive effect upon blood sugar, which can help keep appetite in check. Eating non-starchy vegetables and fruits like apples, pears, and green leafy vegetables may even promote weight loss. Their low glycemic loads prevent blood sugar spikes that can increase hunger.

At least nine different families of fruits and vegetables exist, each with potentially hundreds of different plant compounds that are beneficial to health. Eat a variety of types and colors of produce in order to give your body the mix of nutrients it needs. This not only ensures greater diversity of beneficial plant chemicals but also creates eye-appealing meals.

These are general recommendations by age. Find the right amount for you by getting your

Daily Recommendation*
Toddlers 12 to 23 months ⅔ to 1 cup
Children 2-4 yrs 1 to 2 cups
5-8 yrs 1½ to 2½ cups
Girls 9-13 yrs 1½ to 3 cups
14-18 yrs 2½ to 3 cups
Boys 9-13 yrs 2 to 3½ cups
14-18 yrs 2½ to 4 cups
Women 19-30 yrs 2½ to 3 cups
31-59 yrs 2 to 3 cups
60+ yrs 2 to 3 cups
Men 19-30 yrs 3 to 4 cups
31-59 yrs 3 to 4 cups
60+ yrs 2½ to 3½ cups

The amount that counts as 1 cup of vegetables

The amount that counts as 1 cup of vegetables
Dark-Green Vegetables Broccoli 1 cup, chopped or florets, fresh or frozen
Bitter melon leaves, chrysanthemum leaves, escarole, lambs quarters, nettles, poke greens, taro leaves, turnip greens 1 cup, cooked
Amaranth leaves, beet greens, bok choy, broccoli raab (rapini), chard, collards (collard greens), cress, dandelion greens, kale, mustard greens, spinach, Swiss chard, watercress 1 cup, cooked

2 cups, fresh

Raw leafy greens: Arugula (rocket), basil, cilantro,  dark green leafy lettuce, endive, escarole, mixed greens, mesclun, romaine 2 cups, fresh
Red and Orange Vegetables Carrots 2 medium carrots

1 cup, slices or chopped, fresh, cooked or frozen

1 cup baby carrots

Pimento/Pimiento 3 whole

1 cup

Pumpkin, calabaza 1 cup, mashed, cooked
Red and orange bell peppers 1 large bell pepper

1 cup, chopped, fresh, or cooked

Red chili peppers ¾ cup
Sweet potato 1 large sweet potato, baked

1 cup, sliced or mashed, cooked

Tomatoes 1 large tomato

2 small tomatoes

1 cup, chopped or sliced, fresh, canned, or cooked

100% vegetable juice 1 cup
Winter squash (acorn, butternut, hubbard, kabocha) 1 cup, cubed, cooked
Beans, Peas, and Lentils Dry beans and peas and lentils (such as bayo, black, brown, fava, garbanzo, kidney, lima, mung, navy, pigeon, pink, pinto, soy, or white beans, or black-eyed peas (cow peas) or split peas, and red, brown, and green lentils) 1 cup, whole or mashed, cooked
Starchy Vegetables Breadfruit 1 ½ cups, cooked
Cassava ¾ cup, cooked
Corn, yellow or white 1 large ear of corn

1 cup corn kernels, fresh or frozen

Green peas 1 cup fresh or frozen
Hominy 1 cup, cooked
Plantains ¾ cup, cooked
White potatoes 1 medium white potato, boiled or baked

1 cup, diced, mashed, fresh or frozen

Other Vegetables Avocado 1 avocado
Bamboo shoots 1 cup
Bean sprouts 1 cup, cooked
Cabbage, green, red, napa, savoy 1 cup, chopped or shredded raw or cooked
Cactus pads (nopales) 5 pads

1 cup sliced

Cauliflower 1 cup, pieces or florets raw or cooked, fresh or frozen
Celery 1 cup, diced or sliced, raw or cooked

2 large stalks (11″ to 12″ long)

Cucumbers 1 cup, raw, sliced or chopped
Green or wax beans 1 cup, cooked
Green bell peppers 1 large bell pepper

1 cup, chopped, raw or cooked, fresh or frozen

Lettuce, iceberg or head 2 cups, raw, shredded or chopped
Mushrooms 1 cup, raw or cooked
Okra 1 cup, cooked
Onions 1 cup, chopped, raw or cooked
Summer squash or zucchini 1 cup, cooked, sliced or diced

Health Benefits

All food and beverage choices matter – focus on variety, amount, and nutrition.

  • As part of an overall healthy diet, eating foods such as vegetables that are lower in calories per cup instead of some other higher-calorie food may be useful in helping to lower calorie intake.
  • Eating a diet rich in vegetables and fruits as part of an overall healthy diet may reduce risk for heart disease, including heart attack and stroke.
  • Eating a diet rich in some vegetables and fruits as part of an overall healthy diet may protect against certain types of cancers.
  • Adding vegetables can help increase intake of fiber and potassium, which are important nutrients that many Americans do not get enough of in their diet.

Vegetables are well-known for being good for your health. Most vegetables are low in calories but high in vitamins, minerals and fiber. However, some vegetables stand out from the rest with additional proven health benefits, such as the ability to fight inflammation or reduce the risk of disease.

Which Kind Of Vegetables Are Best According To My Age

1. Spinach

  • This leafy green tops the chart as one of the healthiest vegetables, thanks to its impressive nutrient profile.
  • One cup (30 grams) of raw spinach provides 56% of your daily vitamin A needs plus your entire daily vitamin K requirement — all for just 7 calories (rx).
  • Spinach also boasts a lot of antioxidants, which can help reduce the risk of chronic disease.
  • One study found that dark green leafy vegetables like spinach are high in beta-carotene and lutein, two types of antioxidants that have been associated with a decreased risk of cancer (rx).
  • In addition, a 2015 study found that spinach consumption may be beneficial for heart health, as it may lower blood pressure (rx).

SUMMARY:Spinach is rich in antioxidants that may reduce the risk of chronic disease, as it may reduce risk factors such as high blood pressure.

2. Carrots

  • Carrots are packed with vitamin A, providing 428% of the daily recommended value in just one cup (128 grams) (rx).
  • They contain beta-carotene, an antioxidant that gives carrots their vibrant orange color and could help in cancer prevention (rx).
  • In fact, one study revealed that for each serving of carrots per week, participants’ risk of prostate cancer decreased by 5% (rx).
  • Another study showed that eating carrots may reduce the risk of lung cancer in smokers as well. Compared to those who ate carrots at least once a week, smokers who did not eat carrots had a three times greater risk of developing lung cancer (rx).
  • Carrots are also high in vitamin C, vitamin K and potassium (rx).

SUMMARY:Carrots are especially high in beta-carotene, which can turn into vitamin A in the body. Their high antioxidant content may help reduce the risk of lung and prostate cancer.

3. Broccoli

  • Broccoli belongs to the cruciferous family of vegetables.
  • It is rich in a sulfur-containing plant compound known as glucosinolate, as well as sulforaphane, a by-product of glucosinolate (rx).
  • Sulforaphane is significant in that it has been shown to have a protective effect against cancer.
  • In one animal study, sulforaphane was able to reduce the size and number of breast cancer cells while also blocking tumor growth in mice (rx).
  • Eating broccoli may help prevent other types of chronic disease, too.
  • A 2010 animal study found that consuming broccoli sprouts could protect the heart from disease-causing oxidative stress by significantly lower levels of oxidants (rx).
  • In addition to its ability to prevent disease, broccoli is also loaded with nutrients.
  • A cup (91 grams) of raw broccoli provides 116% of your daily vitamin K needs, 135% of the daily vitamin C requirement and a good amount of folate, manganese and potassium (rx).

SUMMARY:Broccoli is a cruciferous vegetable that contains sulforaphane, a compound that may prevent cancer growth. Eating broccoli may also help reduce the risk of chronic disease by protecting against oxidative stress.

4. Garlic

  • Garlic has a long history of use as a medicinal plant, with roots tracing all the way back to ancient China and Egypt (rx).
  • The main active compound in garlic is allicin, a plant compound that is largely responsible for garlic’s variety of health benefits (rx).
  • Several studies have shown that garlic can regulate blood sugar as well as promote heart health.
  • In one animal study, diabetic rats were given either garlic oil or diallyl trisulfide, a component of garlic. Both garlic compounds caused a decrease in blood sugar and improved insulin sensitivity (rx).
  • Another study fed garlic to participants both with and without heart disease. Results showed that garlic was able to decrease total blood cholesterol, triglycerides, and LDL cholesterol while increasing HDL cholesterol in both groups (rx).
  • Garlic may be useful in the prevention of cancer as well. One test-tube study demonstrated that allicin induced cell death in human liver cancer cells (rx).
  • However, further research is needed to better understand the potential anti-cancer effects of garlic.

SUMMARY:Studies show that garlic may help lower blood triglyceride levels. Some studies have also found that it could decrease blood sugar levels and may have an anti-cancer effect, although more research is needed.

5. Brussels Sprouts

  • Like broccoli, Brussels sprouts are a member of the cruciferous family of vegetables and contain the same health-promoting plant compounds.
  • Brussels sprouts also contain kaempferol, an antioxidant that may be particularly effective in preventing damage to cells (rx).
  • One animal study found that kaempferol protected against free radicals, which cause oxidative damage to cells and can contribute to chronic disease (rx).
  • Brussels sprout consumption can help enhance detoxification as well.
  • One study showed that eating Brussels sprouts led to a 15–30% increase in some of the specific enzymes that control detoxification, which could decrease the risk of colorectal cancer (rx).
  • Additionally, Brussels sprouts are very nutrient-dense. Each serving provides a good amount of many vitamins and minerals, including vitamin K, vitamin A, vitamin C, folate, manganese and potassium (rx).

SUMMARY:Brussels sprouts contain an antioxidant called kaempferol, which may protect against oxidative damage to cells and prevent chronic disease. They may also help enhance detoxification in the body.

6. Kale

  • Like other leafy greens, kale is well-known for its health-promoting qualities, including its nutrient density and antioxidant content.
  • A cup (67 grams) of raw kale contains plenty of B vitamins, potassium, calcium and copper.
  • It also fulfills your entire daily requirement for vitamins A, C, and K (rx).
  • Due to its high amount of antioxidants, kale may also be beneficial in promoting heart health.
  • In a 2008 study, 32 men with high cholesterol drank 150 ml of kale juice daily for 12 weeks. By the end of the study, HDL cholesterol increased by 27%, LDL cholesterol decreased by 10% and antioxidant activity was increased (rx).
  • Another study showed that drinking kale juice can decrease blood pressure and may be beneficial in reducing both blood cholesterol and blood sugar (rx).

SUMMARY:Kale is high in vitamins A, C and K as well as antioxidants. Studies show that drinking kale juice could reduce blood pressure and LDL cholesterol while increasing HDL cholesterol.

7. Green Peas

  • Peas are considered starchy vegetables. This means they have a higher amount of carbs and calories than non-starchy vegetables and may impact blood sugar levels when eaten in large amounts.
  • Nevertheless, green peas are incredibly nutritious.
  • One cup (160 grams) of cooked green peas contains 9 grams of fiber, 9 grams of protein and vitamins A, C and K, riboflavin, thiamin, niacin and folate (rx).
  • Because they are high in fiber, peas support digestive health by enhancing the beneficial bacteria in your gut and promoting regular bowel movements (rx).
  • Moreover, peas are rich in saponins, a group of plant compounds known for their anti-cancer effects (rx).
  • Research shows that saponins may help fight cancer by reducing tumor growth and inducing cell death in cancer cells (rx).

SUMMARY:Green peas contain a good amount of fiber, which helps support digestive health. They also contain plant compounds called saponins, which may have anti-cancer effects.

8. Swiss Chard

  • Swiss chard is low in calories but high in many essential vitamins and minerals.
  • One cup (36 grams) contains just 7 calories yet 1 gram of fiber, 1 gram of protein and lots of vitamins A, C and K, manganese and magnesium (rx).
  • Swiss chard is especially known for its potential to prevent damage caused by diabetes mellitus.
  • In one animal study, chard extract was found to reverse the effects of diabetes by decreasing blood sugar levels and preventing cell damage from disease-causing free radicals (rx).
  • Other animal studies have shown that the antioxidant content of chard extract can protect the liver and kidneys from the negative effects of diabetes (rx, rx).

SUMMARY:Some animal studies show that Swiss chard could protect against the negative effects of diabetes and may decrease blood sugar levels.

9. Ginger

  • Ginger root is used as a spice in everything from vegetable dishes to desserts.
  • Historically, ginger has also been used as a natural remedy for motion sickness (rx).
  • Several studies have confirmed the beneficial effects of ginger on nausea. In a review comprised of 12 studies and nearly 1,300 pregnant women, ginger significantly reduced nausea compared to a placebo (rx).
  • Ginger also contains potent anti-inflammatory properties, which can be helpful in treating inflammation-related disorders like arthritis, lupus or gout (rx).
  • In one study, participants with osteoarthritis who were treated with a concentrated ginger extract experienced reduced knee pain and relief from other symptoms (rx).
  • Further research suggests that ginger could aid in the treatment of diabetes as well.
  • A 2015 study looked at the effects of ginger supplements on diabetes. After 12 weeks, ginger was found to be effective in decreasing blood sugar levels (rx).

SUMMARY:Studies show that ginger could reduce nausea and alleviate inflammation. Ginger supplements may also help decrease blood sugar.

10. Asparagus

  • This spring vegetable is rich in several vitamins and minerals, making it an excellent addition to any diet.
  • Just half a cup (90 grams) of asparagus provides one-third of your daily folate needs.
  • This amount also provides plenty of selenium, vitamin K, thiamin, and riboflavin (rx).
  • Getting enough folate from sources like asparagus can offer protection from disease and can prevent neural tube birth defects during pregnancy (rx, rx).
  • Some test-tube studies also show that asparagus may benefit the liver by supporting its metabolic function and protecting it against toxicity (rx).

SUMMARY:Asparagus is especially high in folate, which may help prevent neural tube birth defects. Test-tube studies have also found that asparagus can support liver function and reduce the risk of toxicity.

11. Red Cabbage

  • This vegetable belongs to the cruciferous family of vegetables and, much like its relatives, is brimming with antioxidants and health-promoting properties.
  • One cup (89 grams) of raw red cabbage contains 2 grams of fiber as well as 85% of the daily vitamin C requirement (rx).
  • Red cabbage is also rich in anthocyanins, a group of plant compounds that contribute to its distinct color as well as a whole host of health benefits.
  • In a 2012 animal study, rats were fed a diet designed to increase cholesterol levels and increase plaque buildup in the arteries. The rats were then given red cabbage extract.
  • The study found that red cabbage extract was able to prevent increases in blood cholesterol levels and protect against damage to the heart and liver (rx).
  • These results were supported by another animal study in 2014 showing that red cabbage could reduce inflammation and prevent liver damage in rats fed a high-cholesterol diet (rx).

SUMMARY:Red cabbage contains a good amount of fiber, vitamin C and anthocyanins. Certain studies show that it may decrease blood cholesterol levels, reduce inflammation and lower the risk of heart and liver damage.

12. Sweet Potatoes

  • Classified as a root vegetable, sweet potatoes stand out for their vibrant orange color, sweet taste and impressive health benefits.
  • One medium sweet potato contains 4 grams of fiber, 2 grams of protein and a good amount of vitamin C, vitamin B6, potassium and manganese (rx).
  • It’s also high in a form of vitamin A called beta-carotene. In fact, one sweet potato fulfills 438% of your daily vitamin A needs (rx).
  • Beta-carotene consumption has been linked to a significant decrease in the risk of certain types of cancer, including lung and breast cancer (rx, rx).
  • Specific types of sweet potatoes may also contain additional benefits. For example, Caiapo is a type of white sweet potato that may have an anti-diabetic effect.
  • In one study, people with diabetes were given 4 grams of Caiapo daily over 12 weeks, leading to a reduction in both blood sugar and blood cholesterol levels (rx).

SUMMARY:Sweet potatoes are high in beta-carotene, which may decrease the risk of some types of cancer. White sweet potatoes could also help reduce blood cholesterol and blood sugar levels.

13. Collard Greens

  • Collard greens are a very nutrient-rich vegetable.
  • One cup (190 grams) of cooked collard greens contains 5 grams of fiber, 4 grams of protein and 27% of your daily calcium needs (rx).
  • In fact, collard greens are one of the best plant sources of calcium available, along with other leafy greens, broccoli and soybeans.
  • Adequate calcium intake from plant sources can promote bone health and has been shown to decrease the risk of osteoporosis (rx).
  • Collard greens are also high in antioxidants and could even reduce your risk of developing certain diseases.
  • One study found that eating more than one serving of collard greens per week was associated with a 57% decreased risk of glaucoma, an eye condition that can lead to blindness (rx).
  • Another study showed that a high intake of vegetables in the Brassica family, which includes collard greens, may decrease the risk of prostate cancer (rx).

SUMMARY:Collard greens are high in calcium, which could reduce the risk of osteoporosis. The regular intake of collard greens has also been associated with a reduced risk of glaucoma and prostate cancer.

14. Kohlrabi

  • Also known as the turnip cabbage or German turnip, kohlrabi is a vegetable related to the cabbage that can be eaten raw or cooked.
  • Raw kohlrabi is high in fiber, providing 5 grams in each cup (135 grams). It’s also full of vitamin C, providing 140% of the daily value per cup (rx).
  • Studies have shown that the antioxidant content of kohlrabi makes it a powerful tool against inflammation and diabetes (rx).
  • In one animal study, kohlrabi extract was able to decrease blood sugar levels by 64% within just seven days of treatment (rx).
  • Though there are different types of kohlrabi available, studies show that red kohlrabi has nearly twice the amount of phenolic antioxidants and displays stronger anti-diabetic and anti-inflammatory effects (rx).

SUMMARY:Kohlrabi is rich in both fiber and vitamin C. Animal studies show that kohlrabi could potentially cause a reduction in blood sugar.

Metabolism of Nutrients – Types, Structure, Functions

Metabolism of Nutrients defines the molecular fate of nutrients and other dietary compounds in humans, as well as outlining the molecular basis of processes supporting nutrition, such as chemical sensing and appetite control. It focuses on the presentation of nutritional biochemistry, and the reader is given a clear and specific perspective on the events that control the utilization of dietary compounds. Slightly over 100 self-contained chapters cover all essential and important nutrients as well as many other dietary compounds with relevance for human health. An essential read for healthcare professionals and researchers in all areas of health and nutrition who want to access the wealth of nutrition knowledge available today in one single source.

Connecting Other Sugars to Nutrient Metabolism

Sugars, such as galactose, fructose, and glycogen, are catabolized into new products in order to enter the glycolytic pathway.

Key Points

When blood sugar levels drop, glycogen is broken down into glucose -1-phosphate, which is then converted to glucose-6-phosphate and enters glycolysis for ATP production.

In the liver, galactose is converted to glucose-6-phosphate in order to enter the glycolytic pathway.

Fructose is converted into glycogen in the liver and then follows the same pathway as glycogen to enter glycolysis.

Sucrose is broken down into glucose and fructose; glucose enters the pathway directly while fructose is converted to glycogen.

Key Terms

  • disaccharide: A sugar, such as sucrose, maltose, or lactose, consisting of two monosaccharides combined together.
  • glycogen: A polysaccharide that is the main form of carbohydrate storage in animals; converted to glucose as needed.
  • monosaccharide: A simple sugar such as glucose, fructose, or deoxyribose that has a single ring.

You have learned about the catabolism of glucose, which provides energy to living cells. But living things consume more than glucose for food. How does a turkey sandwich end up as ATP in your cells? This happens because all of the catabolic pathways for carbohydrates, proteins, and lipids eventually connect into glycolysis and the citric acid cycle pathways.

Metabolic pathways should be thought of as porous; that is, substances enter from other pathways, and intermediates leave for other pathways. These pathways are not closed systems. Many of the substrates, intermediates, and products in a particular pathway are reactants in other pathways. Like sugars and amino acids, the catabolic pathways of lipids are also connected to the glucose catabolism pathways.

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Glycogen Pathway: Glycogen from the liver and muscles, hydrolyzed into glucose-1-phosphate, together with fats and proteins, can feed into the catabolic pathways for carbohydrates.

Glycogen, a polymer of glucose, is an energy-storage molecule in animals. When there is adequate ATP present, excess glucose is shunted into glycogen for storage. Glycogen is made and stored in both the liver and muscles. The glycogen is hydrolyzed into the glucose monomer, glucose-1-phosphate (G-1-P), if blood sugar levels drop. The presence of glycogen as a source of glucose allows ATP to be produced for a longer period of time during exercise. Glycogen is broken down into G-1-P and converted into glucose-6-phosphate (G-6-P) in both muscle and liver cells; this product enters the glycolytic pathway.

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Glycogen Structure: Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogen is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units.

Galactose is the sugar in milk. Infants have an enzyme in the small intestine that metabolizes lactose to galactose and glucose. In areas where milk products are regularly consumed, adults have also evolved this enzyme. Galactose is converted in the liver to G-6-P and can thus enter the glycolytic pathway.

Fructose is one of the three dietary monosaccharides (along with glucose and galactose) which are absorbed directly into the bloodstream during digestion. Fructose is absorbed from the small intestine and then passes to the liver to be metabolized, primarily to glycogen. The catabolism of both fructose and galactose produces the same number of ATP molecules as glucose.

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Fructose Metabolism: Although the metabolism of fructose and glucose share many of the same intermediate structures, they have very different metabolic fates in human metabolism.

Sucrose is a disaccharide with a molecule of glucose and a molecule of fructose bonded together with a glycosidic linkage. The catabolism of sucrose breaks it down to monomers of glucose and fructose. The glucose can directly enter the glycolytic pathway while fructose must first be converted to glycogen, which can be broken down to G-1-P and enter the glycolytic pathway as described above.

Connecting Proteins to Glucose Metabolism Nutrient Metabolism

Excess amino acids are converted into molecules that can enter the pathways of glucose catabolism.

Key Points

Amino acids must be deaminated before entering any of the pathways of glucose catabolism: the amino group is converted to ammonia, which is used by the liver in the synthesis of urea.

Deaminated amino acids can be converted into pyruvate, acetyl CoA, or some components of the citric acid cycle to enter the pathways of glucose catabolism.

Several amino acids can enter the glucose catabolism pathways at multiple locations.

Key Terms

  • catabolism: Destructive metabolism, usually including the release of energy and breakdown of materials.
  • keto acid: Any carboxylic acid that also contains a ketone group.
  • deamination: The removal of an amino group from a compound.

Metabolic pathways should be thought of as porous; that is, substances enter from other pathways and intermediates leave for other pathways. These pathways are not closed systems. Many of the substrates, intermediates, and products in a particular pathway are reactants in other pathways. Proteins are a good example of this phenomenon. They can be broken down into their constituent amino acids and used at various steps of the pathway of glucose catabolism.

Proteins are hydrolyzed by a variety of enzymes in cells. Most of the time, the amino acids are recycled into the synthesis of new proteins or are used as precursors in the synthesis of other important biological molecules, such as hormones, nucleotides, or neurotransmitters. However, if there are excess amino acids, or if the body is in a state of starvation, some amino acids will be shunted into the pathways of glucose catabolism.

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Connection of Amino Acids to Glucose Metabolism Pathways: The carbon skeletons of certain amino acids (indicated in boxes) are derived from proteins and can feed into pyruvate, acetyl CoA, and the citric acid cycle.

Each amino acid must have its amino group removed (deamination) prior to the carbon chain’s entry into these pathways. When the amino group is removed from an amino acid, it is converted into ammonia through the urea cycle. The remaining atoms of the amino acid result in a keto acid: a carbon chain with one ketone and one carboxylic acid group. In mammals, the liver synthesizes urea from two ammonia molecules and a carbon dioxide molecule. Thus, urea is the principal waste product in mammals produced from the nitrogen originating in amino acids; it leaves the body in urine. The keto acid can then enter the citric acid cycle.

When deaminated, amino acids can enter the pathways of glucose metabolism as pyruvate, acetyl CoA, or several components of the citric acid cycle. For example, deaminated asparagine and aspartate are converted into oxaloacetate and enter glucose catabolism in the citric acid cycle. Deaminated amino acids can also be converted into another intermediate molecule before entering the pathways. Several amino acids can enter glucose catabolism at multiple locations.

Oxidation of Carbohydrates, Proteins, and Fats Converge on the Tricarboxylic Acid Cycle

This circular diagram depicts the chemical reactions of the tricarboxylic acid cycle. In a series of eight reactions, the acetyl group of acetyl-coA is completely oxidized to carbon dioxide (CO2), oxaloacetate is regenerated, and the coenzymes NAD+ and FAD are reduced to NADH and FADH2, respectively.

The reactions catalyzed by the dehydrogenases that result in NAD+ and FAD reduction are highlighted. The reaction catalyzed by succinyl-CoA synthetase (in which GTP synthesis occurs) is an example of substrate-level phosphorylation.

Interconversion of energy between reduced coenzymes and O2 directs ATP synthesis, but how (and where) are NADH and FADH2 reduced? In aerobic respiration or aerobiosis, all products of nutrients’ degradation converge to a central pathway in the metabolism, the TCA cycle. In this pathway, the acetyl group of acetyl-CoA resulting from the catabolism of glucose, fatty acids, and some amino acids is completely oxidized to CO2 with concomitant reduction of electron transporting coenzymes (NADH and FADH2). Consisting of eight reactions, the cycle starts with condensing acetyl-CoA and oxaloacetate to generate citrate. The next seven reactions regenerate oxaloacetate and include four oxidation reactions in which energy is conserved with the reduction of NAD+ and FAD coenzymes to NADH and FADH2, whose electrons will then be transferred to O2 through the ETS. In addition, a GTP or an ATP molecule is directly formed as an example of substrate-level phosphorylation. In this case, the hydrolysis of the thioester bond of succinyl-CoA with concomitant enzyme phosphorylation is coupled to the transfer of an enzyme-bound phosphate group to GDP or ADP. Importantly, although O2 does not participate directly in this pathway, the TCA cycle only operates in aerobic conditions because the oxidized NAD+ and FAD are regenerated only in the ETS. Also noteworthy is that TCA cycle intermediates may also be used as the precursors of different biosynthetic processes.The TCA cycle is also known as the Krebs cycle, named after its discoverer, Sir Hans Kreb. Krebs based his conception of this cycle on four main observations made in the 1930s. The first was the discovery in 1935 of the sequence of reactions from succinate to fumarate to malate to oxaloacetate by Albert Szent-Gyorgyi, who showed that these dicarboxylic acids present in animal tissues stimulate O2 consumption. The second was the finding of the sequence from citrate to α-ketoglutarate to succinate, in 1937, by Carl Martius and Franz Knoop. Next was the observation by Krebs himself, working on muscle slice cultures, that the addition of tricarboxylic acids even in very low concentrations promoted the oxidation of a much higher amount of pyruvate, suggesting a catalytic effect of these compounds. And the fourth was Krebs’s observation that malonate, an inhibitor of succinate dehydrogenase, completely stopped the oxidation of pyruvate by the addition of tricarboxylic acids and that the addition of oxaloacetate in the medium in this condition generated citrate, which accumulated, thus elegantly showing the cyclic nature of the pathway.

Pathways for Nutrient Degradation that Converge onto the TCA Cycle

Glycolysis

A linear diagram depicts the chemical reactions of the glycolysis pathway. In a series of ten chemical reactions, a glucose molecule is converted to pyruvate, resulting in the synthesis of energy in the form of ATP.

Glycolysis is the pathway in which one glucose molecule is degraded into two pyruvate molecules. Interestingly, during the initial phase, energy is consumed because two ATP molecules are used up to activate glucose and fructose-6-phosphate. Part of the energy derived from the breakdown of the phosphoanhydride bond of ATP is conserved in the formation of phosphate-ester bonds in glucose-6-phosphate and fructose-1,6-biphosphate (Figure 4).In the second part of glycolysis, the majority of the free energy obtained from the oxidation of the aldehyde group of glyceraldehyde 3-phosphate (G3P) is conserved in the acyl-phosphate group of 1,3- bisphosphoglycerate (1,3-BPG), which contains high free energy. Then, part of the potential energy of 1,3BPG, released during its conversion to 3-phosphoglycerate, is coupled to the phosphorylation of ADP to ATP. The second reaction where ATP synthesis occurs is the conversion of phosphoenolpyruvate (PEP) to pyruvate. PEP is a high-energy compound due to its phosphate-ester bond, and therefore the conversion reaction of PEP to pyruvate is coupled with ADP phosphorylation. This mechanism of ATP synthesis is called substrate-level phosphorylation.

For complete oxidation, pyruvate molecules generated in glycolysis are transported to the mitochondrial matrix to be converted into acetyl-CoA in a reaction catalyzed by the multienzyme complex pyruvate dehydrogenase (Figure 5). When Krebs proposed the TCA cycle in 1937, he thought that citrate was synthesized from oxaloacetate and pyruvate (or a derivative of it). Only after Lipmann’s discovery of coenzyme A in 1945 and the subsequent work of R. Stern, S. Ochoa, and F. Lynen did it become clear that the molecule acetyl-CoA donated its acetyl group to oxaloacetate. Until this time, the TCA cycle was seen as a pathway to carbohydrate oxidation only. Most high school textbooks reflect this period of biochemistry knowledge and do not emphasize how the lipid and amino acid degradation pathways converge on the TCA cycle.

The Fatty Acid Oxidation Pathway Intersects the TCA Cycle

In 1904, Knoop, in a classic experiment, decisively showed that fatty acid oxidation was a process by which two-carbon units were progressively removed from the carboxyl end fatty acid molecule. The process consists of four reactions and generates acetyl-CoA and the acyl-CoA molecule shortened by two carbons, with the concomitant reduction of FAD by enzyme acyl-CoA dehydrogenase and of NAD+ by β-hydroxy acyl-CoA dehydrogenase. This pathway is known as β-oxidation because the β-carbon atom is oxidized prior to when the bond between carbons β and α is cleaved (Figure 6). The four steps of β-oxidation are continuously repeated until the acyl-CoA is entirely oxidized to acetyl-CoA, which then enters the TCA cycle. In the 1950s, a series of experiments verified that the carbon atoms of fatty acids were the same ones that appeared in the acids of the TCA cycle.

Amino Acid Transamination/Deamination Contributes to the TCA Cycle

Two points must be considered regarding the use of amino acids as fuels in energy metabolism. The first is the presence of nitrogen in amino acid composition, which must be removed before amino acids become metabolically useful. The other is that there are at least twenty different amino acids, each of which requires a different degradation pathway. For our purpose here, it is important to mention two kinds of reactions involving amino acids: transamination and deamination. In the first kind of reaction, the enzyme aminotransferases convert amino acids to their respective α-ketoacids by transferring the amino group of one amino acid to an α-ketoacid. This reaction allows the amino acids to be interconverted. The second kind of reaction, deamination, removes the amino group of the amino acid in the form of ammonia. In the liver, the oxidative deamination of glutamate results in α-ketoglutarate (a TCA cycle intermediate) and ammonia, which is converted into urea and excreted. Deamination reactions in other organs form ammonia that is generally incorporated into glutamate to generate glutamine, which is the main transporter of amino groups in blood. Hence, all amino acids through transamination/deamination reactions can be converted into intermediates of the TCA cycle, directly or via conversion to pyruvate or acetyl-CoA (Figure 5).

Function

Role in Glucose Metabolism

The homeostasis of glucose metabolism is carried out by 2 signaling cascades: insulin-mediated glucose uptake (IMGU) and glucose-stimulated insulin secretion (GSIS). The IMGU cascade allows insulin to increase the uptake of glucose from skeletal muscle and adipose tissue and suppresses glucose generation by hepatic cells. Activation of the insulin cascade’s downstream signaling begins when insulin extracellularly interacts with the insulin receptor’s alpha subunit. This interaction leads to conformational changes in the insulin-receptor complex, eventually leading to tyrosine kinase phosphorylation of insulin receptor substrates and subsequent activation of phosphatidylinositol-3-kinase. These downstream events cause the desired translocation of the GLUT-4 transporter from intracellular to extracellular onto skeletal muscle cell’s plasma membrane. Intracellularly, GLUT4 is present within vesicles. The rate at which these GLUT4-vesicles are exocytosed increases due to insulin’s actions or exercise. Thus, by increasing GLUT-4’s presence on the plasma membrane, insulin allows for glucose entry into skeletal muscle cells for metabolism into glycogen.

Role in Glycogen Metabolism

In the liver, insulin affects glycogen metabolism by stimulation of glycogen synthesis. Protein phosphatase I (PPI) is the key molecule in the regulation of glycogen metabolism. Via dephosphorylation, PPI slows the rate of glycogenolysis by inactivating phosphorylase kinase and phosphorylase A. In contrast, PPI accelerates glycogenesis by activating glycogen synthase B.  Insulin serves to increase PPI substrate-specific activity on glycogen particles, in turn stimulating the synthesis of glycogen from glucose in the liver.

There are a variety of hepatic metabolic enzymes under the direct control of insulin through gene transcription. This affects gene expression in metabolic pathways. In gluconeogenesis, insulin inhibits gene expression of the rate-limiting step, phosphoenolpyruvate carboxylase, as well as fructose-1,6-bisphosphatase and glucose-6-phosphatase. In glycolysis, gene expression of glucokinase and pyruvate kinase increases. In lipogenesis, the expression is increased of fatty acid synthase, pyruvate dehydrogenase, and acetyl-CoA carboxylase.

Role in Lipid Metabolism

As previously mentioned, insulin increases the expression of some lipogenic enzymes. This is due to glucose stored as a lipid within adipocytes. Thus, an increase in a fatty acid generation will increase glucose uptake by the cells. Insulin further regulates this process by dephosphorylating and subsequently inhibiting hormone-sensitive lipase, leading to inhibition of lipolysis. Ultimately, insulin decreases serum free fatty acid levels.

Role in Protein Metabolism

Protein turnover rate is regulated in part by insulin. Protein synthesis is stimulated by insulin’s increase in intracellular uptake of alanine, arginine, and glutamine (short-chain amino acids) and gene expression of albumin and muscle myosin heavy chain alpha. Regulation of protein breakdown is affected by insulin’s downregulation of hepatic and muscle cell enzymes responsible for protein degradation. The impacted enzymes include ATP-ubiquitin-dependent proteases, and ATP-independent lysosomal proteases, and hydrolases.

Role in Inflammation and Vasodilation

Insulin’s actions within endothelial cells and macrophages have an anti-inflammatory effect on the body. Within endothelial cells, insulin stimulates the expression of endothelial nitric oxide synthase (eNOS).  eNOS functions to release nitric oxide (NO), which leads to vasodilation. Insulin suppresses nuclear factor-kappa-B (NF-kB) found intracellularly in endothelial cells. Endothelial NF-KB activates the expression of adhesion molecules, E-selectin, and ICAM-1, which release soluble cell adhesion molecules into the circulation. Studies have linked the presence of cell adhesion molecules on vascular endothelium to the development of atherosclerotic arterial plaques.

Insulin suppresses the generation of O2 radicals and reactive oxygen species (ROS). Within the macrophage, insulin inhibits NADPH oxidase expression by suppressing one of its key components, p47phox.  NADPH oxidase aids in generating oxygen radicals, which activate the inhibitor of NF-kB kinase beta (IKKB). IKKB phosphorylates IkB, leading to its degradation. This degradation releases NF-kB, allowing for its translocation in the macrophage’s nucleus. Once in the nucleus, NF-kB stimulates gene transcription of pro-inflammatory proteins that are released into the circulation, such as inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-8 (IL-8), monocyte chemoattractant protein (MCP-1), and matrix metalloproteinase (MMP)

References

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Nutrients – Types, Mechanism, Health Benefit

Nutrients are chemical substances required by the body to sustain basic functions and are optimally obtained by eating a balanced diet. There are six major classes of nutrients essential for human health: carbohydrates, lipids, proteins, vitamins, minerals, and water. Carbohydrates, lipids, and proteins are considered macronutrients and serve as a source of energy. Water is required in large amounts but does not yield energy. Vitamins and minerals are considered micronutrients and play essential roles in metabolism. Vitamins are organic micronutrients classified as either water-soluble or fat-soluble. The essential water-soluble vitamins include vitamins B1, B2, B3, B5, B6, B7, B9, B12, and C. The essential fat-soluble vitamins include vitamins A, E, D, and K. Minerals are inorganic micronutrients. Minerals can classify as macrominerals or microminerals. Macrominerals are required in amounts greater than 100 mg per day and include calcium, phosphorous, magnesium, sodium, potassium, and chloride. Sodium, potassium, and chloride are also electrolytes. Microminerals are those nutrients required in amounts less than 100 mg per day and include iron, copper, zinc, selenium, and iodine. This article will review the following biochemical aspects of the essential nutrients: fundamentals, cellular, molecular, function, testing, and clinical significance.

Digestive Systems and Nutrition

Animals use the organs of their digestive systems to extract important nutrients from food they consume, which can later be absorbed.

Key Points

Animals obtain lipids, proteins, carbohydrates, essential vitamins, and minerals from the food they consume.

The digestive system is composed of a series of organs, each with a specific, yet related function, that work to extract nutrients from food.

Organs of the digestive system include the mouth, esophagus, stomach, small intestine, and the large intestine.

Accessory organs, such as the liver and pancreas, secrete digestive juices into the gastrointestinal tract to assist with food breakdown.

Key Terms

  • digestion: the process, in the gastrointestinal tract, by which food is converted into substances that can be utilized by the body
  • macromolecule: a very large molecule, especially used in reference to large biological polymers (e.g. nucleic acids and proteins)
  • alimentary canal: the organs of a human or an animal through which food passes; the digestive tract

All living organisms need nutrients to survive. While plants can obtain the molecules required for cellular function through the process of photosynthesis, most animals obtain their nutrients by the consumption of other organisms. At the cellular level, the biological molecules necessary for animal function are amino acids, lipid molecules, nucleotides, and simple sugars. The food consumed consists of protein, fat, and complex carbohydrates, but the requirements of each are different for each animal.

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Balanced human diet: For humans, fruits and vegetables are important in maintaining a balanced diet. Both of these are an important source of vitamins and minerals, as well as carbohydrates, which are broken down through digestion for energy.

Animals must convert these macromolecules into the simple molecules required for maintaining cellular functions, such as assembling new molecules, cells, and tissues. The conversion of the food consumed to the nutrients required is a multi-step process involving digestion and absorption. During digestion, food particles are broken down to smaller components which will later be absorbed by the body.

Digestive System

The digestive system is one of the largest organ systems in the human body. It is responsible for processing ingested food and liquids. The cells of the human body all require a wide array of chemicals to support their metabolic activities, from organic nutrients used as fuel to the water that sustains life at the cellular level. The digestive system not only effectively chemically reduces the compounds in food into their fundamental building blocks, but also acts to retain water and excrete undigested materials. The functions of the digestive system can be summarized as follows: ingestion (eat food), digestion (breakdown of food), absorption (extraction of nutrients from the food), and defecation (removal of waste products).

The digestive system consists of a group of organs that form a closed tube-like structure called the gastrointestinal tract (GI tract) or the alimentary canal. For convenience, the GI tract is divided into upper GI tract and lower GI tract. The organs that make up the GI tract include the mouth, the esophagus, the stomach, the small intestine, and the large intestine. There are also several accessory organs that secrete various enzymes into the GI tract. These include the salivary glands, the liver, and the pancreas.

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Generalized animal digestive system: This diagram shows a generalized animal digestive system, detailing the different organs and their functions.

Challenges to Human Nutrition

One of the challenges in human nutrition is maintaining a balance between food intake, storage, and energy expenditure. Imbalances can have serious health consequences. For example, eating too much food while not expending much energy leads to obesity, which in turn will increase the risk of developing illnesses such as type-2 diabetes and cardiovascular disease. The recent rise in obesity and related diseases means that understanding the role of diet and nutrition in maintaining good health is more important than ever.

Carbohydrates: Sources, Uses in the Body, and Dietary Requirements

Carbohydrates, which break down to glucose, are a major source of energy for humans but are not essential nutrients.

Key Points

Carbohydrates include such items as fruits, grains, beans, and potatoes, along with sugars and sugared foods.

While fat is a better source of energy, the brain cannot burn fat and instead requires glucose.

Polysaccharides (complex carbs) are difficult for humans to break down but are useful as fiber to enhance the digestive process.

Government agencies recommend a dietary intake of 45–65% or 55–75% of carbohydrates to meet daily energy needs.

Of daily carbohydrate intake, only 10% should be simple carbs or sugars.

Key Terms

  • glucose: A simple monosaccharide (sugar) with a molecular formula of C6H12O6; it is a principle source of energy for cellular metabolism.
  • carbohydrate: A sugar, starch, or cellulose that is a food source of energy for an animal or plant; a saccharide.
  • saccharide: The unit structure of carbohydrates, of general formula CnH2nOn. Either the simple sugars or polymers such as starch and cellulose. The saccharides exist in either a ring or short chain conformation, and typically contain five or six carbon atoms.

EXAMPLES

Daily food intake that includes 8–10 fruit and vegetable servings (not starchy potatoes or grains, such as corn and rice) will not only provide plenty of energy but will also keep glucose levels in balance.

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Carbohydrates are a class of macromolecule: Grain products are rich sources of carbohydrates.

Foods high in carbohydrates include fruits, sweets, soft drinks, bread, pasta, beans, potatoes, bran, rice, and cereals. Carbohydrates are a common source of energy in living organisms, however, carbohydrate is not an essential nutrient in humans.

Carbohydrates are not necessary building blocks of other molecules, and the body can obtain all its energy from protein and fats. The brain and neurons generally cannot burn fat for energy but use solely glucose or ketones. Humans can synthesize some glucose (in a set of processes known as “gluconeogenesis”) from specific amino acids or from the glycerol backbone in triglycerides and, in some cases, from fatty acids. Carbohydrates and protein contain 4 kilocalories per gram, while fats contain 9 kilocalories per gram. In the case of protein, this is somewhat misleading as only some amino acids are able to undergo conversion into useful energy forms.

Organisms typically cannot metabolize all types of carbohydrates to yield energy. Glucose is a nearly universal and accessible source of calories. Many organisms also have the ability to metabolize other monosaccharides and disaccharides, though glucose is preferred. Polysaccharides are also common sources of energy. Even though these complex carbohydrates are not very digestible, they may comprise important dietary elements for humans. Called “dietary fiber,” these carbohydrates enhance digestion, among other benefits.

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Glucose Molecule: Image of a glucose molecule containing a fixed ratio of carbon, hydrogen and oxygen.

Based on the effects on risk of heart disease and obesity, the Institute of Medicine (IOM) recommends that American and Canadian adults get between 45–65% of dietary energy from carbohydrates. The Food and Agriculture Organization (FAO) and World Health Organization (WHO) jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).

Lipids: Sources, Uses in the Body, and Dietary Requirements

Fats store energy, facilitate absorption of fat-soluble vitamins, aid brain growth and development, and protect against many diseases.

Key Points

Vitamins A, D, E, and K should be taken with some dietary fat in order to facilitate their absorption and activity.

Humans cannot synthesize omega-6 and omega-3 fatty acids, so these fats must be obtained from the diet.

Omega-6 fatty acids are found in many foods, while omega-3 fatty acids are found in walnuts and are especially abundant in fatty fish.

Omega-3 fatty acids have many positive health benefits including reduced rates of cancer, cardiovascular disease, mental illness, and dementia.

Studies of dietary fat intake have found no link between the percentage of calories obtained from fats and the risk of cancer, heart disease, or obesity.

Trans fats, such as those present in partially hydrogenated vegetable oils, are a risk factor for cardiovascular disease.

Key Terms

  • phospholipids: Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers.
  • trans fats: Trans fats are unsaturated fats generated by physical agents such as heat or pressure that can lead to a variety of health problems.
  • fatty acid: Fatty acids can be saturated or unsaturated and are usually derived from triglycerides or phospholipids.

EXAMPLES

College students require optimal brain function, which is supported by fatty fish and walnuts.

Most of the fats found in food are triglycerides, cholesterol, and phospholipids. Some dietary fat is necessary for the absorption of fat-soluble vitamins (A, D, E, and K) and carotenoids. Humans and other mammals require fatty acids such as linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid), because they cannot be synthesized from simple precursors in the diet.

Both omega-6 and omega-3 are 18-carbon polyunsaturated fatty acids that differ in the number and position of their double bonds. Most vegetable oils (safflower, sunflower, and corn oils) are rich in linoleic acid. Alpha-linolenic acid is found in the green leaves of plants, selected seeds, nuts, and legumes, and particularly in flax, rapeseed, walnut, and soy. Fish oils are especially rich in the longer-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Numerous studies have shown that the consumption of omega-3 fatty acids has positive benefits in terms of infant development, cancer, cardiovascular disease, and mental illnesses such as depression, attention-deficit hyperactivity disorder, and dementia. In contrast, the consumption of trans fats, such as those present in partially hydrogenated vegetable oils, are now known to be a risk factor for cardiovascular disease.

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Omega-3 Fatty Acid: Docosahexaenoic acid (DHA) is an omega-3 fatty acid. It is essential for the proper functioning of the brain in both adults and infants. DHA concentrations in breast milk ranged from 0.07-1.0% of total fatty acids and are influenced by the amount of fatty fish in the mother’s diet. In the U.S., infant formula has been supplemented with DHA since 2001. Research suggests that DHA contributes to numerous nervous system functions such as visual acuity, neurogenesis, and synaptogenesis and that it lowers the risk for cardiovascular disease. It is highly concentrated in the brain and eye.

Several studies have suggested that total dietary fat intake is linked to obesity and diabetes. However, influential studies like the Women’s Health Initiative Dietary Modification Trial (an eight-year study of 49,000 women), as well as the Nurses’ Health Study and the Health Professionals Follow-up Study, have revealed no such link between the percentage of calories from fat and risk of cancer, heart disease, or weight gain. The Nutrition Source, a website maintained by the Department of Nutrition at the Harvard School of Public Health, summarizes the current evidence on the impact of dietary fat as follows: “Detailed research—much of it done at Harvard—shows that the total amount of fat in the diet isn’t really linked with weight or disease.”

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Salmon: Salmon is an excellent source of omega-3 fatty acids.

Proteins: Sources, Uses in the Body, and Dietary Requirements

Proteins are composed of 20 different amino acids, about half of which are essential, meaning they must be obtained from the diet.

Key Points

Protein-based foods (plant and animal) provide amino acids; however, the best source of essential amino acids is animal.

If the diet does not provide adequate protein, the body will obtain what it needs from itself, especially from its own muscles.

While adequate protein is required for building skeletal muscle and other tissues, there is ongoing debate regarding the use and necessity of high-protein diets in anaerobic exercise, in particular weight training and bodybuilding.

This use of protein as a fuel is particularly important under starvation conditions as it allows the body’s own proteins to be used to support life.

Key Terms

  • amino acid: Any of the twenty naturally occurring α-amino acids (having the amino, and carboxylic acid groups on the same carbon atom), and a variety of side chains, that combine, via peptide bonds, to form proteins.
  • denaturation: Denaturation is a process in which proteins or nucleic acids lose their tertiary and secondary structure which is present in their native state, by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), or heat.
  • protein: Any of numerous large, complex naturally-produced molecules composed of one or more long chains of amino acids, in which the amino acid groups are held together by peptide bonds.

Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals (including humans) must obtain some of the amino acids from the diet. The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids. Key enzymes that synthesize certain amino acids are not present in animals. One example is aspartokinase, which catalyzes the first step in the synthesis of lysine, methionine, and threonine from aspartate.

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Amino Acid: Ball-and-stick model of the cystine molecule, an amino acid formed from two cysteine molecules.

In animals, amino acids are obtained through the consumption of foods containing protein. Ingested proteins are then broken down into amino acids through digestion, which typically involves denaturation of the protein through exposure to acid and hydrolysis by enzymes called proteases. Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body’s own proteins to be used to support life, particularly those found in muscle. Amino acids are also an important dietary source of nitrogen.

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Protein: Muscle meat, such as steak, is an excellent source of the essential amino acids the body needs to create all necessary proteins.

A high-protein diet is often recommended by bodybuilders and nutritionists to help efforts to build muscle and lose fat. It should not be confused with low-carb diets, such as the Atkins Diet, which are not calorie-controlled and which often contain large amounts of fat. While adequate protein is required for building skeletal muscle and other tissues, there is ongoing debate regarding the use and necessity of high-protein diets in anaerobic exercise in particular weight training and bodybuilding. Extreme protein intake (in excess of 200g per day), coupled with an inadequate intake of other calorie sources (fat or carbohydrates), can cause a form of metabolic disturbance and death commonly known as rabbit starvation.

Relatively little evidence has been gathered regarding the effect of long-term high intake of protein on the development of chronic diseases. Increased load on the kidney is a result of an increase in the reabsorption of NaCl. This causes a decrease in the sensitivity of tubuloglomerular feedback, which, in turn, results in an increased glomerular filtration rate. This increases pressure in glomerular capillaries. When added to any additional renal disease, this may cause permanent glomerular damage.

Food Requirements and Essential Nutrients

Essential nutrients are those that cannot be created by an animal’s metabolism and need to be obtained from the diet.

Key Points

The animal diet needs to be well-balanced in order to ensure that all necessary vitamins and minerals are being obtained.

Vitamins are important for maintaining bodily health, making bones strong, and seeing in the dark.

Water-soluble vitamins are not stored by the body and need to be consumed more regularly than fat-soluble vitamins, which build up within body tissues.

Essential fatty acids need to be consumed through the diet and are important building blocks of cell membranes.

Nine of the 20 amino acids cannot be synthesized by the body and need to be obtained from the diet.

Key Terms

  • nutrient: a source of nourishment, such as food, that can be metabolized by an organism to give energy and build tissue
  • catabolism: destructive metabolism, usually including the release of energy and breakdown of materials
  • vitamin: any of a specific group of organic compounds essential in small quantities for healthy human growth, metabolism, development, and body function

Food Requirements

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A balanced diet: For humans, a balanced diet includes fruits, vegetables, grains, and protein. Each of these food sources provides different nutrients the body cannot make for itself. These include vitamins, omega 3 fatty acids, and some amino acids.

What are the fundamental requirements of the animal diet? The animal diet should be well balanced and provide nutrients required for bodily function along with the minerals and vitamins required for maintaining structure and regulation necessary for good health and reproductive capability.

Organic Precursors

The organic molecules required for building cellular material and tissues must come from food. Carbohydrates or sugars are the primary sources of organic carbons in the animal body. During digestion, digestible carbohydrates are ultimately broken down into glucose and used to provide energy through metabolic pathways. The excess sugars in the body are converted into glycogen and stored in the liver and muscles for later use. Glycogen stores are used to fuel prolonged exertions, such as long-distance running, and to provide energy during food shortages. Excess digestible carbohydrates are stored by mammals in order to survive famine and aid in mobility.

Another important requirement is that of nitrogen. Protein catabolism provides a source of organic nitrogen. Amino acids are the building blocks of proteins and protein breakdown provides amino acids that are used for cellular function. The carbon and nitrogen derived from these become the building block for nucleotides, nucleic acids, proteins, cells, and tissues. Excess nitrogen must be excreted, as it is toxic. Fats add flavor to food and promote a sense of satiety or fullness. Fatty foods are also significant sources of energy because one gram of fat contains nine calories. Fats are required in the diet to aid the absorption of fat-soluble vitamins and the production of fat-soluble hormones.

Essential Nutrients

While the animal body can synthesize many of the molecules required for function from the organic precursors, there are some nutrients that need to be consumed from food. These nutrients are termed essential nutrients: they must be eaten as the body cannot produce them.

Vitamins and minerals are substances found in the food we eat. Your body needs them to be able to work properly and for growth and development. Each vitamin has its own special role to play. For example, vitamin D (added to whole milk or naturally occurring in sardines), helps make bones strong, while vitamin A (found in carrots) helps with night vision. Vitamins fall into two categories: fat-soluble and water-soluble. The fat-soluble vitamins dissolve in fat and can be stored in your body, whereas the water-soluble vitamins need to dissolve in water before your body can absorb them; therefore, the body cannot store them.

Fat-soluble vitamins are found primarily in foods that contain fat and oil, such as animal fats, vegetable oils, dairy foods, liver, and fatty fish. Your body needs these vitamins every day to enable it to work properly. However, you do not need to eat foods containing these every day. If your body does not need these vitamins immediately, they will be stored in the liver and fat tissues for future use. This means that stores can build up; if you have more than you need, fat-soluble vitamins can become harmful. Some fat-soluble vitamins include vitamin A, vitamin K, vitamin D, and vitamin E. Unlike the other fat-soluble vitamins, vitamin D is difficult to obtain in adequate quantities in a normal diet; therefore, supplementation may be necessary.

Water-soluble vitamins are not stored in the body; therefore, you need to have them more frequently. If you have more then you need, the body rids itself of the extra vitamins during urination. Because the body does not store these vitamins, they are generally not harmful. Water-soluble vitamins are found in foods that include fruits, vegetables, and grains. Unlike fat-soluble vitamins, they can be destroyed by heat. This means that sometimes these vitamins can often be lost during cooking. This is why it is better to steam or grill these foods rather then boil them. Some water-soluble vitamins include vitamin B6, vitamin B12, vitamin C, biotin, folic acid, niacin, and riboflavin.

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Sea buckthorn seed oil: Sea buckthorn seed oil contains many vital nutrients.

The omega-3 alpha-linolenic acid and the omega-6 linoleic acid are essential fatty acids needed to synthesize some membrane phospholipids. Many people take supplements to ensure they are obtaining all the essential fatty acids they need. Sea buckthorn contains many of these fatty acids and is also high in vitamins. Sea buckthorn can be used to treat acne and promote weight loss and wound healing.

Minerals are inorganic essential nutrients that must also be obtained from food. Among their many functions, minerals help in cell structure and regulation; they are also considered co-factors. In addition to vitamins and minerals, certain amino acids must also be procured from food and cannot be synthesized by the body. These amino acids are the “essential” amino acids. The human body can synthesize only 11 of the 20 required amino acids. The rest must be obtained from food.

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Amino Acids: There are 20 known amino acids. Animals can make only 11, so the others must be obtained through the diet. Meats are the best source of amino acids, although some amino acids can also be obtained from vegetables and grains.

Fundamentals Nutrition

Carbohydrates

Carbohydrates are essential macronutrients that are the primary source of energy for humans; 1 gram of carbohydrate contains 4 kcal of energy. Carbohydrates also play roles in gut health and immune function. Carbohydrates are present in plant-based foods like grains, fruits, vegetables, and milk. Carbohydrates are ingested in the form of simple carbohydrates, like monosaccharides and disaccharides, or complex carbohydrates, like oligosaccharides and polysaccharides. Monosaccharides are the basic building blocks of all carbohydrates and include glucose, fructose, and galactose. Glucose is the primary form to which carbohydrates become metabolized in humans. Disaccharides contain two sugar units and include lactose, sucrose, and maltose. Lactose is a carbohydrate found in milk, and sucrose is basic table sugar. Oligosaccharides consist of 3 to 10 sugar units and include raffinose and stachyose, which are in legumes. Polysaccharides include greater than ten sugar units and consist of starches, glycogen, and fibers, like pectin and cellulose. Starches like amylose are in grains, starchy vegetables, and legumes and consist of glucose monomers. Glycogen is the storage form of glucose in animals and is present in the liver and muscle, but there is little to none in the diet. Fibers are plant polysaccharides like pectin and cellulose found in whole grains, fruits, vegetables, and legumes but are not digestible by humans. However, they play a major role in gut health and function and can be digested by microbiota in the large intestine. For healthy children and adults, carbohydrates should make up approximately 45 to 65% of energy intake based on the minimum required glucose for brain function. The recommended fiber intake is greater than 38 g for men and 25 g for women, which is the intake that research has observed to lower the risk of coronary artery disease. Some carbohydrates are more nutritious than others. Optimal carbohydrate intake consists of fiber-rich, nutrient-dense whole grains, fruits, vegetables, legumes, and added sugar.

Proteins

Proteins are essential macronutrients that contribute to structural and mechanical function, regulate processes in the cells and body, and provide energy if necessary. Proteins are composed of amino acids and are available in food sources like meats, dairy foods, legumes, vegetables, and grains. 1 gram of protein contains 4 kcal of energy. The recommended protein intake is 0.8 to 1 gram per kilogram of body weight per day. For healthy children ages 1 to 3, ages 4 to 18, and adults, approximately 5 to 20%, 10 to 30%, and 10 to 35% of daily energy intake should come from protein, respectively, based on the adequate amount needed for nitrogen equilibrium.

Lipids

Lipids are essential macronutrients that are the main source of stored energy in the body, contribute to cellular structure and function, regulate temperature, and protect body organs. Lipids are found in fats, oils, meats, dairy, and plants and consumed mostly in the form of triglycerides. One gram of fat contains 9 kcal of energy. For healthy children ages 1 to 3, ages 4 to 18, and adults, approximately 30 to 40%, 25 to 15%, and 20 to 35% of daily energy intake should come from fat, respectively. Approximately 5 to 10% and 0.6 to 1.2% of the daily fat energy intake should consist of n-6 polyunsaturated fatty acids (linoleic acid) and n-3 polyunsaturated fatty acids (α-linolenic acid), respectively.

Vitamin

  • Vitamin B1 (Thiamin) – Thiamin, or vitamin B1, is an essential water-soluble vitamin that acts as a coenzyme in carbohydrate and branched-chain amino acid metabolism. Thiamin is in food sources such as enriched and whole grains, legumes, and pork. The RDA (Recommended Dietary Allowance) of thiamin for adults is 1.1 mg/day for women and 1.2 mg/day for men.
  • Vitamin B2 (Riboflavin) – Riboflavin, or vitamin B2, is an essential water-soluble vitamin that acts as a coenzyme in redox reactions. Riboflavin is present in food sources such as enriched and whole grains, milk and dairy products, leafy vegetables, and beef. The RDA of riboflavin for adults is 1.1 mg/day for women and 1.3 mg/day for men.
  • Vitamin B3 (Niacin) – Niacin, or vitamin B3, is an essential water-soluble vitamin that acts as a coenzyme to dehydrogenase enzymes in the transfer of the hydride ion and an essential component of the electron carriers NAD and NADP. Niacin is present in enriched and whole grains and high protein foods like meat, milk, and eggs. The RDA of niacin for adults is 14 mg/day of NEs (niacin equivalents) for women and 16 mg/day of NEs for men.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid, or vitamin B5, is an essential water-soluble vitamin that acts as a key component of coenzyme A and phosphopantetheine, which are crucial to fatty acid metabolism. Pantothenic acid is widespread in foods. The AI (adequate intake) of pantothenic acid for adults is 5 mg/day.
  • Vitamin B6 (Pyridoxine)  – Vitamin B6, or pyridoxine, is an essential water-soluble vitamin that acts as a coenzyme for amino acid, glycogen, and sphingoid base metabolism. Vitamin B6 is widespread among food groups. The RDA for vitamin B6 for adults is 1.3 mg/day.
  • Vitamin B7 (Biotin) – Biotin, or vitamin B7, is an essential water-soluble vitamin that acts as a coenzyme in carboxylation reactions dependent on bicarbonate. Biotin is found widespread in foods, especially egg yolks, soybeans, and whole grains. The AI of biotin for adults is 30 mcg/day.
  • Vitamin B9 (Folate)  – Folate, or vitamin B9, is an essential water-soluble vitamin that acts as a coenzyme in single-carbon transfers in nucleic acid and amino acid metabolism. Folate is in enriched and fortified grains, green leafy vegetables, and legumes. The RDA of folate for adults is 400 mcg/day of DFEs. The recommendation is that women of childbearing age consume an additional 400 mcg/day of folic acid from supplements or fortified foods to decrease the risk of neural tube defects.
  • Vitamin B12 (Cobalamin) – Vitamin B12, or cobalamin, is an essential water-soluble vitamin that acts as coenzymes for the crucial methyl transfer reaction in converting homocysteine to methionine and the isomerization reaction that occurs in the conversion of L-methylmalonyl-CoA to succinyl-CoA. Vitamin B12 is only present in animal products because it is a product of bacteria synthesis. Many foods are also fortified with synthetic vitamin B12. The RDA of vitamin B12 for adults is 2.4 mcg/day. It is recommended for older adults to meet their RDA with fortified foods or supplements because many are unable to absorb naturally occurring vitamin B12.
  • Vitamin C (Ascorbic Acid) – Vitamin C, or ascorbic acid, is an essential water-soluble vitamin that acts as a reducing agent in enzymatic reactions and nonenzymatically as a soluble antioxidant. Vitamin C is found primarily in fruits and vegetables, except for animal organs like the liver and kidneys. The RDA of vitamin C for adult women and men is 75 mg/day and 90 mg/day, respectively. Smokers require an additional 35 mg/day of vitamin C.
  • Vitamin A (Retinol) – Vitamin A, or retinol, is an essential fat-soluble vitamin that plays numerous roles in vision, cellular differentiation, gene expression, growth, the immune system, bone development, and reproduction. Vitamin A is found primarily in animal products. Fruits and vegetables are a source of provitamin A carotenoids that can be converted to retinol in the body at a lesser amount. The RDA for vitamin A for adults is 900 mcg/day for males and 700 mcg/day for females.
  • Vitamin D (Cholecalciferol) –Vitamin D, or cholecalciferol, is an essential fat-soluble vitamin that plays an essential role in calcium metabolism, cell growth and development, and bone health. Vitamin D can be found in fish oils and in small amounts in plants in its less biologically active form. Interestingly, vitamin D synthesis occurs in the skin with exposure to UV light making dietary sources unnecessary in certain cases. The RDA for vitamin D for adults is 10 to 15 mcg/day.
  • Vitamin E (Tocopherol) – Vitamin E, or tocopherol, is a fat-soluble vitamin that is an antioxidant and may play roles in cell signaling, platelet aggregation, and vasodilation. Vitamin E, in the form of α-tocopherol, is found in certain vegetable oils, including sunflower, safflower, canola, and olive oil, whole grains, nuts, and green leafy vegetables. The RDA for vitamin E for adults is 15 mg/day.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K is an essential fat-soluble vitamin that is the coenzyme in the carboxylation of glutamic acid to form γ-carboxyglutamic acid reaction, which is essential to the proteins involved in blood coagulation. Vitamin K is present in green leafy vegetables, canola oil, and soybean oil. The RDA of vitamin K for adults is 120 mcg/day for men and 90 mcg/day for women.

Mineral

  • Calcium – Calcium is an essential macromineral responsible for numerous structural components such as bones and teeth and physiological mechanisms in the body. Calcium exists in dietary sources such as dairy, cereals, legumes, and vegetables. The RDA for calcium for adults is 1,000 mg/day.
  • Magnesium – Magnesium is an essential macromineral responsible for numerous functions in the body, including signaling pathways, energy storage, and transfer, glucose metabolism, lipid metabolism, neuromuscular function, and bone development. Magnesium is present in food sources such as fruits, vegetables, whole grains, legumes, nuts, dairy, meat, and fortified foods like cereal. The adult RDA for magnesium is 400 mg/day.
  • Phosphorus – Phosphorus is an essential macromineral that is a structural component of bones and teeth, DNA, RNA, and plasma membrane of cells. It is also critical metabolically to produce and store energy. Phosphorus is pervasive throughout food sources, with the greatest contributors being milk, dairy, meat, and poultry. Phosphorus is also an additive in processed foods as a preservative. The RDA for phosphorus for adults is 700 mg/day.
  • Sodium – Sodium is an essential macromineral and electrolyte that plays critical roles in cellular membrane transport, water balance, nerve innervation, and muscle contraction as the most abundant extracellular cation. Sodium is available in dietary sources such as salt, processed foods, meat, milk, eggs, and vegetables. The AI for sodium for adults is 1,500 mg/day; however, the average sodium intake in industrialized nations is 2 or 3 fold by comparison, at 3,000 to 4,500 mg/day.
  • Potassium – Potassium is an essential macromineral and electrolyte that plays critical roles in muscle contraction, nerve innervation, blood pH balance, and water balance as the most abundant intracellular cation. Potassium is obtainable in dietary sources such as fruits and vegetables. The AI for potassium is for adults is 4,700 mg/day.
  • Chloride – Chloride is an essential macromineral and electrolyte that plays critical roles in digestion, muscular activity, water balance, and acid-base balance as the most abundant extracellular anion in the body. Dietary chloride is almost always present in dietary sources associated with sodium in the form of NaCl or table salt. Chloride is in processed foods, meat, milk, eggs, and vegetables. The AI for chloride for adults is 1,500 mg/day.
  • Iron – Iron is an essential trace mineral that has a critical role in oxygen transport and energy metabolism. Dietary iron is from sources such as meat, fortified grains, and green leafy vegetables. Animal foods contain a more bioavailable form of iron called heme iron, while plant foods and fortified grains contain a less bioavailable form called non-heme iron. The RDA for iron for adults is 8 to 18 mg/day.
  • Zinc – Zinc is an essential trace mineral that functions structurally in proteins and catalytically as a component of over 300 different enzymes. Zinc appears in a variety of foods, especially shellfish and red meat. The RDA for zinc for adults is 10 mg/day.
  • Copper – Copper is an essential trace mineral that acts as a component of numerous proteins, including many important enzymes. Copper is in a variety of food sources but the highest concentrations in organ meats, nuts, seeds, chocolate, and shellfish. The RDA for copper for adults is 1 mg/day.
  • Iodine – Iodine is an essential trace mineral necessary for thyroid hormone synthesis. Iodine is present in meats and plant foods based on the soil content of the food production region. Otherwise, iodized salt is the main food source of iodine in regions with low soil iodine content. The adult RDA for iodine is 150 mcg/day.
  • Selenium – Selenium is an essential trace mineral that is an essential component of selenoproteins that play biological roles in antioxidant defense and anabolic processes in the human body. Selenium occurs in grains and vegetables, but the amounts vary based on the selenium content in the soil that the grains and vegetables were grown in. Brazil nuts are known for having high concentrations of selenium. The RDA for selenium for adults is 55 mcg/day.

Cellular

Carbohydrates

Carbohydrate digestion occurs in the mouth and small intestine with salivary amylase, pancreatic amylase, and brush border enzymes. Human carbohydrate digesting enzymes catalyze hydrolysis reactions that break the bonds between monomers. However, given fibers have beta bonds, they are indigestible by human enzymes, so some end up getting digested by bacterial enzymes in the large intestine, and the remainder is excreted in the feces. In the mouth, salivary amylase begins to break down the polysaccharide starch into the disaccharide maltose, which both contain monomers of glucose. Carbohydrate digestion bypasses the stomach and continues in the small intestine via pancreatic amylase and brush border enzymes on the microvilli. Pancreatic amylase continues to break down starches into maltose. The brush border enzymes include maltase, sucrase, and lactase. Maltase hydrolyzes maltose into two glucose monomers. Sucrase hydrolyzes sucrose into glucose and fructose. Lactase hydrolyzes lactose into glucose and galactose.

Monosaccharides pass through intestinal epithelial cells via facilitated diffusion and active transport to enter the bloodstream. Fructose is absorbed via facilitated diffusion by GLUT5 and released via facilitated diffusion by GLUT2. Glucose and galactose are absorbed along with sodium via active transport by the symporter sodium-glucose transporter 1 and are released via facilitated diffusion by GLUT2. The monomers enter the portal vein and travel to the liver. When fructose and galactose enter the liver, they must first be converted to glucose to be metabolized for energy. These can be converted into intermediates of the glycolysis pathway, glucose-6-phosphate or fructose-6-phosphate, to directly enter the glycolysis pathway or the substrate of glycogenesis, glucose-1-phosphate, to be stored as glycogen.

Glucose metabolism requires the following B vitamins to act as coenzymes: thiamine (B1), riboflavin (B2), and niacin (B3). Glucose metabolism begins in the cytoplasm of cells with the anaerobic process of glycolysis when one 6-carbon glucose molecule is partially oxidized into two 3-carbon pyruvate molecules. During the process, there is a net yield of two ATP and two NADH, where they will carry the electrons to the electron transport chain, eventually producing ATP. NADH is derived from niacin. ATP is the main source of cellular energy due to its high energy bonds between phosphate groups, which are released when broken via hydrolysis.

In the absence of oxygen, which can happen during strenuous exercise or in cells without mitochondria, lactate dehydrogenase catalyzes the conversion of pyruvate to lactate, which can then go back to the liver to be converted back to pyruvate and undergo gluconeogenesis to create glucose. Then, the glucose can go back to the muscle cells and go through glycolysis, again releasing two ATP molecules. This is called the Cori cycle and shows how lactate, the waste product of skeletal muscles, can be converted to glucose in hepatocytes and then be used for energy back in the skeletal muscles.

In the presence of oxygen, pyruvate will travel to the mitochondrial matrix, where pyruvate dehydrogenase will catalyze the oxidation and decarboxylation of two 3-carbon molecules of pyruvate from glycolysis into two 2-carbon molecules of acetyl-CoA. Pyruvate dehydrogenase uses thiamine pyrophosphate, or TPP, as a coenzyme. In addition, two carbon dioxide molecules and two NADH molecules are produced, and the NADH molecules will carry electrons to the electron transport chain to ultimately produce ATP. Pyruvate decarboxylation is the link between glycolysis and the citric acid cycle.

The citric acid cycle, also known as the TCA cycle and the Krebs cycle, occurs in the mitochondrial matrix where the 2-carbon acetyl-CoA will join 4-carbon oxalate to produce 6-carbon citrate, which gets degraded to produce the energetic molecules GTP, NADH, and FADH2. The cycle will continue so long as there is an input of acetyl-CoA because citrate eventually gets converted back to oxalate. Two pyruvates from glycolysis will release 2 GTP, 6 NADH, and 2 FADH molecules. FADH is derived from riboflavin. NADH and FADH2 will travel to the electron transport chain, where ATP will be synthesized via oxidative phosphorylation.

Oxidative phosphorylation begins at the electron transport chain along the inner membrane of the mitochondrion. Four protein complexes I-IV are embedded along the membrane and function to pump protons from the mitochondrial matrix to the intermembrane space to create an electrochemical gradient through a chain of redox reactions. Protein complex I receive electrons from NADH to pump hydrogen across the inner membrane. FADH2 drops electrons off at protein complex II, and protons get pumped across at protein complex III. One molecule of NADH generates three ATP molecules, while one molecule of FADH2 only generates two molecules of ATP.  When enough protons fill up the intermembrane space, an electrochemical gradient occurs. At protein complex IV, oxygen acts as the final electron acceptor, forming water. Through chemiosmosis, protons will flow from the intermembrane space through the hydrophilic tunnel of ATP synthase back to the matrix. The proton motive force generates energy that allows ATP synthase to condense ADP + Pi into high-energy ATP. Overall, this process generates 34 ATP molecules per molecule of glucose and is by far the most efficient way to produce energy.

Proteins

Protein digestion begins in the stomach, where they are broken down by the protease enzyme pepsin. First, gastric parietal cells will release hydrochloric acid, which will denature proteins and convert inactive pepsinogen to active pepsin. Pepsin digests proteins by hydrolyzing peptide bonds between amino acids to form large polypeptides or oligopeptides. Protein digestion continues in the small intestine. In response to the acidic chyme from the stomach, the hormones cholecystokinin and secretin are synthesized in the duodenum. These hormones trigger pancreatic cells to secrete bicarbonate and proenzymes into the intestine. The proenzymes trypsinogen, procarboxypeptidase, and chymotrypsinogen are converted into their active enzyme forms trypsin, carboxypeptidase, and chymotrypsin in a cascade of enzymatic reactions. Trypsin, carboxypeptidase, and chymotrypsin digest polypeptides into tripeptides, dipeptides, and free amino acids that can be absorbed in the small intestine.

Peptide and amino acid absorption occur across epithelial cells in the small intestine via transporters. Some amino acids can travel across the epithelium paracellularly, while others require amino acid transporters that vary based on the specific amino acid and mechanism in which they transport. Tripeptides and dipeptides are transported into the epithelial cell via PEPT1 coupled with the electrochemical gradient produced by the Na+/H+ exchanger on the brush border membrane. Intracellular peptides finish breaking down tripeptides and dipeptides into free amino acids. Free amino acids will exit the basolateral membrane of the epithelial cell and enter the bloodstream at the portal vein to the liver.

Amino acids can be metabolized via transamination for amino acid interconversion or deamination for the oxidation of the carbon skeleton for energy or excretion. For amino acid interconversion, pyridoxine (B6), cobalamin (B12), and folate (B9) are required. For amino acid oxidation, pyridoxine (B6), cobalamin (B12), and biotin (B7) are required. Amino acids can undergo transamination to enter the TCA cycle in glucose metabolism. Certain amino acids like alanine can be transaminated by an aminotransferase enzyme with the coenzyme PLP, which is derived from pyridoxine, to form pyruvate. Other amino acids can be transaminated by an aminotransferase enzyme with PLP to form α-ketoglutarate, an intermediate in the TCA cycle. Some amino acids can be transaminated by an aminotransferase enzyme with PLP to form oxaloacetate, which is an intermediate in the TCA cycle. Other amino acids can be oxidized with enzymes that require biotin and vitamin B12 as coenzymes or from succinyl-CoA, which is an intermediate in the TCA cycle. When the carbon skeletons of amino acids become degraded for energy, they are deaminated, and the nitrogen group is excreted in the form of urea.

Lipids

Limited digestion of lipids occurs in the mouth and stomach with the enzymes lingual lipase and gastric lipase, respectively. However, most ingested lipids arrive at the duodenum of the small intestine undigested. The presence of lipids in the duodenum stimulates the release of enzymes from the pancreas and bile from the gallbladder. Bile emulsifies that lipids preparing them for digestion by pancreatic lipase. Pancreatic lipase hydrolyzes triglycerides to monoglycerides and free fatty acids. Lipids are absorbed via simple diffusion. Short-chain fatty acids and glycerol move directly into the portal circulation and bind to albumin. Long-chain fatty acids, mono/diglycerides, cholesterol, and phospholipids combine with bile to form micelles allowing them to be soluble in the hydrophilic environment and then leave the micelle and enter the intestinal mucosa cell. In the intestinal cell, long-chain fatty acids are re-esterified to form triglycerides. Triglycerides combine with cholesterol, phospholipids, and other proteins to form chylomicrons. The chylomicrons will leave the intestinal cell and enter the lymph system, eventually entering the bloodstream through the thoracic duct.

Lipoproteins carry lipids throughout the bloodstream, and the enzyme lipoprotein lipase frees up fatty acids to be taken up by cells. In the bloodstream, the chylomicrons can deliver the dietary fatty acids to body cells, where they will form triglycerides and the remaining lipids to the liver to travel to other cells or be excreted. In the liver, triglycerides, cholesterol, phospholipids, and proteins will combine to form VLDL, which will leave the liver to deliver lipids, mainly in the form of triglycerides, to cells in the bloodstream. As VLDL delivers triglycerides to cells, it begins to shrink and become LDL. LDL continues to carry lipids to cells, but the lipids are mainly in the form of cholesterol. LDL binds to LDL receptors of cells for cholesterol to be taken up. The remaining lipids will leave cells in the form of HDL, where they will carry lipids back to the liver for either reuse or excretion. In the cells, lipids can be metabolized for energy by entering at different points of the glucose metabolism pathway. Triglycerides are broken down into glycerol and free fatty acids. Glycerol can be converted to pyruvate and catabolized for energy. Free fatty acids can be oxidized to acetyl-CoA to enter the citric acid cycle.

  • Vitamin B1 (Thiamin) – Thiamin absorption occurs mainly in the jejunum of the small intestine. Higher concentrations are absorbed via passive diffusion, while lower concentrations are absorbed via an active, carrier-mediated system that involves phosphorylation. In the blood, thiamin is transported in the erythrocytes and plasma. A small percentage of thiamin is absorbed, while the remainder is excreted in the urine.
  • Vitamin B2 (Riboflavin) – Thiamin is mainly consumed as FMN and FAD bound to a food protein. In the stomach, the acidic environment releases the coenzymes FMN and FAD from the protein. Most absorption of riboflavin occurs in the small intestine via an active or facilitated transport system. FMN and FAD must first be hydrolyzed to riboflavin by nonspecific pyrophosphatases to be absorbed. Riboflavin is transported in the plasma mainly bound to albumin and is excreted in the urine.
  • Vitamin B3 (Niacin) – At low concentrations, niacin is absorbed in the small intestine via sodium-ion-dependent facilitated diffusion. At high concentrations, niacin is absorbed in the small intestine via passive diffusion. Niacin can be transported freely in the blood in the forms of nicotinic acid or nicotinamide. Cells and tissues can take up niacin via passive diffusion or with the use of transporters. Niacin is excreted in urine as 1-methyl nicotinamide or NAM.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid is absorbed via active transport at low concentrations and passive transport at high concentrations in the small intestine. Pantothenate kinase catalyzes the synthesis of CoA from pantothenate. CoA plays an important role in the citric acid cycle in the forms of acetyl-CoA and succinyl-CoA. CoA can be hydrolyzed to pantothenate for excretion. Pantothenic acid is excreted in the urine.
  • Vitamin B6 (Pyridoxine)  – The main dietary form of vitamin B6 is pyridoxal phosphate or PLP. For PLP to be absorbed in the small intestine, it must first undergo phosphatase-mediated hydrolysis to enter the small intestine in its nonphosphorylated form. Pyridoxal, or PL, crosses the enterocyte via passive diffusion to enter the bloodstream to the liver. In the liver, PL is converted back to PLP by the enzyme PL kinase. PLP is the main circulating form of vitamin B6 and is transported in the blood bound to albumin. The majority of PLP in the body is found in the muscle. Vitamin B6 is excreted in the urine in the form of 4-pyridoxic acid.
  • Vitamin B7 (Biotin) – Biotin can be ingested as free biotin or protein-bound biotin. In the small intestine, an enzyme called biotinidase releases biotin from its covalent bond to the protein allowing it to be absorbed. Biotin is absorbed in the small intestine through a sodium-dependent transporter. Biotin is transported through the bloodstream to the liver, mostly unbound as free biotin. Biotin and biotin metabolites are excreted in the urine.
  • Vitamin B9 (Folate)  – Food folates are polyglutamate derivatives and must be hydrolyzed to the monoglutamate forms before absorption. The monoglutamate form of folate is absorbed in the small intestine via active transport. Pharmacological doses of folic acid from supplements or fortified foods are absorbed via passive transport. Folate is transported in the bloodstream to the liver in the form of 5-methyl-tetrahydrofolate. Folate is mostly bound to albumin in the bloodstream. Most ingested folate is used or stored. Any dietary folate not absorbed is excreted in feces.
  • Vitamin B12 (Cobalamin)  – Small amounts of vitamin B12 are absorbed through a coordinated process of the GI tract, given naturally occurring B12 is bound to a protein that must be released for absorption. First, in the stomach, the presence of acid and pepsin causes the dissociation of food-bound vitamin B12 from its proteins. Then R-proteins or haptocorrins, secreted by the salivary glands, bind to vitamin B12 to protect it from stomach acid. In the small intestine, pancreatic proteases degrade R-proteins to allow B-12 to bind to intrinsic factor, which is secreted by gastric parietal cells. Intrinsic factor attaches B12 to specific ileal mucosa receptors allowing the complex to be internalized by endocytosis into the enterocyte and released into the bloodstream where it is bound to transcobalamin I, II, or III. 50% of transcobalamin II bound B12 is taken up by the liver, where it is stored while the remainder is transported to other tissues. B12 is excreted in bile, but most of it ends up reabsorbed.
  • Vitamin C (Ascorbic Acid) – The absorption, tissue distribution, and excretion of vitamin C are tightly regulated by tissue-specific active transporters SVCT-1 and SCVT-2. Ascorbic acid is absorbed into the enterocyte by SVCT-1 and enters the bloodstream via SVCT-2. Other tissues take up ascorbic acid via SVCT-1 and/or SCVT-2. Vitamin C is excreted in the urine at intakes greater than 400 mg/day. Vitamin C is most concentrated in the brain, eyes, and adrenal gland.
  • Vitamin A (Retinol) – Vitamin A is ingested both in the form of retinol and provitamin A carotenoids. In the small intestine, retinol and provitamin A carotenoids enter the mucosal cell after combining with bile to form a micelle. Retinol binds to cellular retinol-binding protein (CRBP) II within the intestinal mucosal cells to form a retinol-CRBP II complex. Then, lecithin retinol aminotransferase esterifies CRBP II retinol with a fatty acid to form CRBP-retinyl palmitate. The retinol esters will be incorporated with other lipids and apoproteins to form a chylomicron. The chylomicron will leave the intestinal cell and enter the lymph system and eventually enter the blood. β-carotene, a provitamin A carotenoid, is converted to retinoic acid inside the intestinal cells and is able to directly enter the bloodstream where it attaches to albumin to be transported to the liver.
  • Vitamin D (Cholecalciferol) – Vitamin D is obtained mainly through UV-B-induced production in the skin. A minor amount of vitamin D is obtained through dietary intake. In the skin, vitamin D3, or cholecalciferol, is synthesized when 7-dehydrocholesterol is exposed to UV-B light from the sun. Vitamin D3 is transferred to the liver to be further metabolized. Through dietary intake, vitamin D3 is absorbed in the small intestine via incorporation into a micelle to enter the intestinal cells and incorporate into chylomicrons to leave the intestinal cells to enter the lymph system and eventually enter circulation the thoracic duct. In the liver, vitamin D3 enters a hepatocyte and is hydroxylated into 25-OH vitamin D3, which is catalyzed by the enzyme 25-hydroxylase. Then, 25-OH vitamin D3 bind to vitamin D-binding protein, or DBP, to leave the hepatocytes and be transported to the kidney for an additional hydroxylation reaction. In the kidney, 25-OH vitamin D3 is hydroxylated to 1,25-(OH)2 vitamin D3, which is catalyzed by the enzyme 1-hydroxylase. 1,25-(OH)2 vitamin D3 is also known as calcitriol, which is considered the active form of vitamin D. 1,25-(OH)2 vitamin D3 bound to DBP is released to the bone, immune cells, and liver cells.
  • Vitamin E (Tocopherol) – Through dietary intake, vitamin E is absorbed in the small intestine via incorporation into a micelle to enter the intestinal cells and incorporate into a chylomicron to leave the intestinal cells and enter the lymph system and eventually enter circulation the thoracic duct. Vitamin E is transported in remnant chylomicrons to the liver, where it is taken up by a hepatocyte. In the hepatocyte, α-tocopherol transfer protein incorporates α-tocopherols into very low-density lipoproteins, or VLDLs, to transport to peripheral tissues. In circulation, lipoprotein lipase (LPL) catalyzes the conversion of VLDL to LDL to HDL. The cellular uptake of α-tocopherol takes place with the uptake of lipoproteins via receptor-mediated endocytosis. Most α-tocopherol is stored in adipose tissue. The remaining tocopherols and tocotrienols are excreted with bile in feces.
  • Vitamin K (Phylloquinone; Menaquinone) – Through dietary intake, vitamin K1 and K2 are absorbed in the small intestine via incorporation into a micelle to enter the intestinal cells and incorporation into a chylomicron to leave the intestinal cells and enter the lymph system and eventually enter circulation at the thoracic duct. Vitamin K1 and K2 are transported in remnant chylomicrons to the liver where it is taken up by a hepatocyte. In the hepatocyte, vitamin K1 and K2 are incorporated into very low-density lipoproteins, or VLDLs, to transport to peripheral tissues. In circulation, lipoprotein lipase (LPL) catalyzes the conversion of VLDL to LDL to HDL. The cellular uptake of vitamin K1 and K2 takes place with the uptake of lipoproteins via receptor-mediated endocytosis. Vitamin K is stored predominantly in the liver in the form of menaquinone and is excreted in the urine and feces.
  • Calcium – The intestine, kidney, bone, and parathyroid gland work together to tightly regulate calcium balance in the body. The majority of calcium is absorbed in the small intestine via paracellular diffusion. The remainder of calcium is absorbed transcellular through the calcium channel TRPV6 when luminal calcium levels are low. Calcium is transported in the bloodstream in three forms: 48% ionized as free Ca2+, 46% bound to the protein albumin, and 7% complexed with citrate, phosphate, or sulfate. In low blood calcium concentration conditions, the parathyroid gland is stimulated to release parathyroid hormone (PTH). PTH then stimulates the kidneys to increase calcium reabsorption in the proximal convoluted tubule. PTH also stimulates the kidneys to convert 25-OH D3 into 1,25(OH)2 D3, or calcitriol. The increased calcitriol and PTH in the blood travel to the bone and stimulate the resorption of calcium and phosphorus from the bone. Calcitriol also stimulates the small intestine to increase calcium absorption. As a result, blood calcium is increased. In high blood calcium conditions, the thyroid gland releases the hormone calcitonin, preventing calcium mobilization from the bone, thus reducing blood calcium levels. 99% of the calcium in the body is found in the bones and teeth, while the remainder is found in soft tissues and plasma both intracellularly and extracellularly. Most calcium is reabsorbed in the kidney, but the remainder is excreted in urine and feces.
  • Magnesium – Magnesium is absorbed in the small intestine through paracellular diffusion and transcellular active transport via TRPM6 and TRMP7. At normal magnesium intakes, 30% of intestinal magnesium absorption occurs via transcellular transport. When magnesium intakes are lower, more magnesium is absorbed via transcellular transport. When magnesium intakes are higher, more magnesium is absorbed through paracellular diffusion. Magnesium is transported in the blood as free Mg2+(60%), protein-bound (30%), and complexed to citrate, phosphate, or sulfate (10%). The kidneys control magnesium homeostasis. About 70% of serum magnesium is available for glomerular filtration, and 96% of the filtered magnesium is reabsorbed in the kidneys through several mechanisms in the proximal tubule, ascending limb, and distal tubule. The remaining magnesium is excreted in the urine. 99% of magnesium in the body is stored intracellularly in bone, muscle, and soft tissues, while 1% of magnesium in the body is found in extracellular fluid.
  • Phosphorus –  The phosphorus is absorbed in the small intestine into the enterocyte via two processes: active transport by the apical Na+ phosphate transporter NaPi-IIb and paracellular diffusion. Phosphorous leaves the enterocyte to enter the bloodstream via facilitated diffusion. The kidney plays a role in phosphorus homeostasis through the reabsorption of inorganic phosphate from the glomerular filtrate in the proximal convoluted tubule. Approximately 75 to 85% of phosphorus is reabsorbed per day, and the remainder is excreted in the urine. Phosphorus homeostasis can also be regulated secondary to that of calcium with resorption from the bone due to high PTH and calcitriol levels. Throughout the body, phosphorus is distributed 85% in the skeleton, 0.4% in the teeth, 14% in the soft tissue, 0.3% in the blood, and 0.3% in the extravascular fluid.
  • Sodium – Sodium is absorbed in the small intestine across the brush border membrane of the enterocyte via sodium-glucose cotransporter 1 (SGLT1). SGLT 1 is an active transporter that absorbs 2 sodium ions and 1 glucose across the brush border membrane of the enterocyte. Sodium is then transported out of the enterocyte into the bloodstream across the basolateral membrane via the sodium-potassium pump, or ATPase. The sodium-potassium pump uses ATP to transport 3 sodium ions out of the enterocyte and 2 potassium ions into the enterocyte. Sodium and water balance are closely linked and maintained by the kidneys. Half of the sodium in the body is found in extracellular fluid, while around 10% is found in intracellular fluid. The remaining 40% of sodium is found in the skeleton. Small losses of sodium can occur through urine, feces, and sweat.
  • Potassium – Most of the dietary potassium is absorbed in the small intestine via passive transport. The kidney maintains potassium homeostasis. About 90% of the potassium consumed is excreted in the urine, with the remaining small amount excreted in stool and sweat. Most of the potassium content in the body is found in the intracellular space of the skeletal muscle.
  • Chloride – Chloride absorption occurs in the lumen of the small intestine via three distinct mechanisms: paracellularly through passive transport, the coupling of Na+/H+ and Cl−/HCO3− exchangers, and HCO3−-dependent Cl− absorption. Chloride is principally found in extracellular fluid. The kidneys regulate chloride concentration. Around 99% of chloride is reabsorbed in the proximal tubule of the kidneys both paracellularly and transcellular via the Cl−/HCO3− exchanger. The remainder of chloride can be excreted in urine, feces, or sweat.
  • Iron – Iron consumed from food can be present in two forms: heme and nonheme iron. 90% of dietary iron consists of nonheme iron, which is far less bioavailable than heme iron. Iron is absorbed in the small intestine in the duodenum. Given nonheme iron is often present in the form of ferric iron, it must be reduced to the ferrous form prior to enterocyte uptake with the ferric reductase enzyme DCYTB. The apical surface of the enterocyte contains divalent metal transporter 1 (DMT1), which transports ferrous iron into the enterocyte. On the basolateral membrane of the enterocyte, ferroportin releases ferrous iron to hephaestin, which oxidizes ferrous iron to ferric iron so it can bind to the transporting protein transferrin in portal circulation. Ferroportin is the main regulatory point of entry for iron in the body. Iron is stored in the liver bound to ferritin, where it can be sequestered to bone marrow for erythropoiesis or red blood cell formation. Macrophages in the reticuloendothelial system of the liver, spleen, and bone marrow can ingest old red blood cells to recycle iron to be stored in the liver. There is no specific excretory system for iron. Iron loss can only occur secondary to the exfoliation of epithelial cells in the skin and gastrointestinal tract in addition to red blood cell loss from the gastrointestinal tract.
  • Zinc – Zinc is absorbed in the small intestine via carrier-mediated transport, with ZIP4 taking zinc up into the intestinal cell and ZNT1 releasing it into the bloodstream. Zinc is bound to albumin in circulation. Zinc transporters are pervasive throughout tissues in the body and play a role in maintaining zinc homeostasis. Zinc is excreted in feces.
  • Copper – Copper absorption mainly occurs in the small intestine. Copper is taken up by enterocytes with copper transporter 1 (CTR1), which is a copper importer located at the apical membrane of intestinal cells and most tissues. Copper is exported from the enterocytes into the blood by the exporter ATP7A. In portal circulation, most of the copper is bound to the transporter protein ceruloplasmin. Copper is taken up by the liver when copper-bound ceruloplasmin binds to ceruloplasmin receptors. In the hepatocytes, protein metallochaperones serve to assign and transport copper to specific pathways throughout the body. Copper is exported from the hepatocyte via the exporter ATP7B. Excess copper is secreted in the bile, which gets excreted in the feces.
  • Iodine – Iodine can be ingested in many chemical forms. Iodide is rapidly and almost completely absorbed in the stomach and small intestine. Iodate, which is used in iodized salt, is reduced in the gut and then absorbed as iodide. In circulation, iodine is taken up mainly by the thyroid gland and kidney. Iodine uptake by the thyroid depends on iodine intake, whereas uptake by the kidney remains fairly constant. Iodine is excreted in the urine. Most of the body’s iodine is stored in the thyroid to be used in thyroid hormone synthesis.
  • Selenium – The mechanism of selenium absorption is not well known. Selenium absorption occurs in the small intestine via mechanisms dependant upon the form of selenium. The absorption of inorganic selenate occurs through active transport with a sodium pump. The absorption of inorganic selenite occurs via passive diffusion. Organic selenomethionine and selenocysteine are absorbed via an active transport mechanism similar to that of neutral amino acids like methionine. Selenium is absorbed into the portal bloodstream from the enterocyte and is transported to the liver in multiple forms. Selenite is taken up by erythrocytes and reduced by glutathione reductase to selenide, which is transported in the plasma bound to albumin. Selenium can also be transported in the form of selenoprotein P. Sometimes, selenium may bind to LDL and VLDL. Selenium is stored in tissues in the form of selenomethionine with variable densities in the liver, muscle, kidney, plasma, and other organs. Selenium excretion via urine in the form of methylselenol.

Molecular

Carbohydrates

Carbohydrates are organic molecules made up of carbon, hydrogen, and oxygen. Carbohydrates are classified based on their chemistry: individual monomer characteristics, degree of polymerization, and type of linkages (α or β). Given this classification, carbohydrates subdivide into three main groups: sugars (degree of polymerization = 1 to 2), oligosaccharides (degree of polymerization = 3 to 10), and polysaccharides (degree of polymerization more than 10). Sugars include monosaccharides and disaccharides. The most common monosaccharides are glucose, fructose, and galactose. The most common disaccharides are sucrose, lactose, and maltose. Examples of oligosaccharides include maltodextrins, raffinose, and polydextrose. Polysaccharides include starches and non-starch polysaccharides. Starches include digestible amylose due to its alpha-linked monosaccharides. Non-starch polysaccharides include non-digestible cellulose due to their β-linked monosaccharides.

Proteins

Proteins are polymers of amino acids. Amino acids are organic molecules composed of carbon, hydrogen, oxygen, and nitrogen. The general structure of an amino acid consists of a central carbon surrounded by hydrogen, an amino group, a carboxylic acid group, and a side chain “R.” Each amino acid has a unique side chain. Nine essential amino acids must come from dietary sources: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The body can make eleven non-essential amino acids from precursors: alanine, arginine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, and tyrosine. There are four structure levels in a protein: primary, secondary, tertiary, and quaternary. The primary structure of a protein is a chain of amino acids connected by peptide bonds; this determines the subsequent structures and biological functions of the protein. The secondary structure of a protein consists of hydrogen bonding within amino acid chains that create either an α-helix or β-sheet conformation. The tertiary structure of a protein derives from attractions between α-helices and β-sheets of a polypeptide resulting in a three-dimensional arrangement of a protein. The quaternary structure of an amino acid consists of a spatial arrangement of multiple polypeptides in a protein.

Lipids

Lipids are organic molecules that share the common property of being hydrophobic. Dietary lipids are often in the forms of triglycerides, phospholipids, cholesterol, and fatty acids. Fatty acids are classified as saturated or containing no carbon-carbon double bonds, or unsaturated, or containing at least one carbon-carbon double bond. Saturated fatty acids have higher melting points than unsaturated fatty acids, making them solid at room temperature, unlike liquid unsaturated fatty acids. Triglycerides are composed of one 3-carbon glycerol backbone and three fatty acids. Phospholipids contain a phosphate head connected to a glycerol molecule, connected to two fatty acids. Cholesterol is a sterol that is composed of a hydrocarbon ring structure.

  • Vitamin B1 (Thiamin) – Thiamin consists of pyrimidine and thiazole rings that are linked by a methylene bridge. Thiamin exists in a variety of phosphorylated forms. Its main form is thiamin pyrophosphate or TPP.
  • Vitamin B2 (Riboflavin) – The basic chemical structure of riboflavin consists of a flavin group formed by the tricyclic heterocyclic isoalloxazine and a ribitol sugar group. The main coenzyme forms of riboflavin are flavin mononucleotide or FMN and flavin adenine dinucleotide, or FAD.
  • Vitamin B3 (Niacin) – Niacin refers to nicotinamide, nicotinic acid, and other derivatives. The basic chemical structure of nicotinic acid consists of a pyridine ring with a substituted carboxylic acid group. The chemical structure of nicotinamide consists of a pyridine ring with a substituted amide group. The main coenzyme forms of niacin are nicotinamide adenine dinucleotide or NAD and nicotinamide adenine dinucleotide phosphate or NADP.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid is a water-soluble vitamin synthesized from the condensation reaction of pantoic acid and β-alanine in only plants and bacteria. Pantothenic acid serves to transfer and carry acyl groups.
  • Vitamin B6 (Pyridoxine)  – Vitamin B6 is a generic term for six related compounds: pyridoxal (PL), pyridoxamine (PM, pyridoxine (PN), and their respective 5’-phosphatase forms (PLP, PMP, and PNP). The major forms of vitamin B6 in animal tissues are PLP and PMP.
  • Vitamin B7 (Biotin) – Biotin’s chemical structure consists of a heterobicyclic ring of radio and thiophene with a valeric acid side chain.
  • Vitamin B9 (Folate) – Folate is the generic term for the different forms of vitamin B9 that function in single-carbon transfers. The most oxidized and stable form of folate called folic acid is in vitamin supplements. It consists of a p-aminobenzoic acid molecule bound to a pteridine ring on one side and a glutamic acid molecule on the other side. Naturally occurring folates found in food, called food folate, are pteroylpolyglutamates, which contain between one and six additional glutamate molecules connected by a peptide linkage to glutamate’s γ-carboxyl.
  • Vitamin B12 (Cobalamin) – Cobalamin, or vitamin B12, is a generic term for a group of cobalt-containing compounds with a corrin ring attached to 5,6-dimethylbenzimidazole, a sugar ribose, and a phosphate. The two cobalamins that are active in human metabolism as coenzymes are methylcobalamin and 5-deoxyadenosylcobalamin.
  • Vitamin C (Ascorbic Acid) – Vitamin C, or ascorbic acid, chemically is a simple carbohydrate with an ene-diol structure that makes it an essential water-soluble electron donor. The main form of vitamin C found in foods is its reduced form – ascorbic acid. Ascorbate is the main circulating form of vitamin C in the body.
  • Vitamin A (Retinol) – Vitamin A is a generic descriptor for compounds that exhibit the biological activity of retinol and provitamin A carotenoids. Retinol is an unsaturated 20-carbon cyclic alcohol. Provitamin A carotenoids exhibit a 40-carbon basal structure with cyclic end groups and a conjugated system of double bonds.
  • Vitamin D (Cholecalciferol) – Vitamin D3, or cholecalciferol, had a chemical structure that contains three steroid rings and an eight-carbon side chain. The structure derives from cholesterol.
  • Vitamin E (Tocopherol) – The term vitamin E encompasses eight lipophilic compounds that include four tocopherols and four tocotrienols, each of which has a designation as α-, β-, γ-, and δ-. Each of these compounds contains a chromanol ring and a lipophilic tail. Tocotrienols differ from tocopherols with their unsaturated side chains. α-tocopherol is the only form of vitamin E that is known to reverse deficiency symptoms.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K occurs naturally in two main forms: K1, or phylloquinone, and K2, or menaquinone, which has many different forms. Also, vitamin K occurs in the synthetic form of vitamin K3, or menadione, which contains only the 2-methyl-1, a 4-naphthoquinone nucleus common to all forms of vitamin K. The natural forms differ by the number of isoprenoid units in their isoprenoid side chains.
  • Calcium – Calcium is an alkaline earth metal cation found in the form of Ca2+. Calcium is a critical divalent cation in intracellular and extracellular fluid.
  • Magnesium – Magnesium is an alkaline earth metal cation found in the form of Mg2+. Magnesium is the second most abundant intracellular cation in the body.
  • Phosphorus – Phosphorous is a multivalent nonmetal that occurs in both inorganic and organic forms throughout the body. The organic forms of phosphorus include phospholipids and various phosphate esters. The inorganic forms of phosphorus include phosphate ions, protein-bound phosphate, and calcium, sodium, or magnesium-bound phosphate. Most phosphorus exists in the form of an inorganic free phosphate ion (PO42- or PO43-).
  • Sodium – Sodium is an alkali metal cation found in the form of Na+. Sodium is the major extracellular cation in the body.
  • Potassium – Potassium is an alkali metal cation found in the form of K+. Potassium is the major intracellular cation in the body.
  • Chloride – Chloride is a nonmetal anion found in the form of Cl-. Chloride is the body’s principal anion making up 70% of the body’s total anion content and serves as the most important extracellular anion in the body.
  • Iron – Iron is a transition metal element. Iron exists in two main oxidation states: Fe2+ and Fe3+. The more bioavailable form of iron is its reduced form ferrous iron, or Fe2+, due to its solubility. The less bioavailable form of iron is its oxidized form ferric iron, or Fe3+, due to its lack of solubility. Heme iron is contained in the protoporphyrin ring of hemoglobin, myoglobin, and cytochromes and is highly bioavailable. Nonheme iron can be found in molecules like iron-sulfur enzymes and ferritin and is less bioavailable.
  • Zinc – Zinc is a metal that exists in the form of Zn2+. With the 2+ charge, zinc is a strong electron acceptor in biological systems.
  • Copper – Copper is a transition metal that exists in the forms of Cu+ and Cu2+. Cu+ is the cuprous reduced form of copper. Cu2+ is the cupric oxidized form of copper. Copper is absorbed into cells in its reduced form but is ingested and travels through the bloodstream in its oxidized form.
  • Iodine – Iodine is a nonmetal element identified by its distinct violet vapor. Iodine is consumed and absorbed in its reduced form of iodide (I-). Iodine is also consumable in its oxidized form of iodate (IO3-), as well as when it is organically bound to thyroxine (T4) and triiodothyronine (T3).
  • Selenium – Selenium is present in nature in both organic and inorganic forms. The main organic forms of selenium are selenomethionine and selenocysteine. The inorganic forms of selenium are selenite (SeO32-), selenide (Se2−), selenate (SeO42-), and selenium element (Se).

Function

Macronutrients – Carbohydrates, Proteins, Lipids

Macronutrients mainly function to supply energy. Carbohydrates function as the main source of cellular energy from the human diet and are particularly essential to supply energy to the glucose-dependent brain and nervous system. Fiber plays a role in lowering cholesterol by binding to bile and promoting gut health. Proteins function less favorably as a source of energy because they play crucial roles in regulating body processes and contributing majorly to cell and body structure. Proteins particularly function as hormones, enzymes, transporters, and antibodies. Lipids function as a source of stored energy, contribute to cell function and structure and protects body organs. Water acts as a solvent for chemical reactions, a medium for nutrient transport, and a thermoregulator.

  • Vitamin B1 (Thiamin) – The coenzyme form of thiamin, or TPP, is involved in the following types of metabolic reactions: decarboxylation of α-keto acids and transmetalation. These occur in carbohydrate and branched-chain amino acids metabolism.
  • Vitamin B2 (Riboflavin) – Riboflavin functions as a component of the metabolically essential coenzymes FMN and FAD. FMN and FAD can serve as intermediates in electron transfer in redox reactions. As coenzymes, FAD and FMN are often bound to enzymes that are oxidases and dehydrogenases.
  • Vitamin B3 (Niacin) – Niacin functions as a component of the metabolically essential coenzymes NAD and NADP. These coenzymes act as hydride ion acceptors or donors in biological redox reactions. They also serve as coenzymes for dehydrogenases.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid functions as a supporter of the synthesis and maintenance of coenzyme A, a cofactor and acyl group carrier for other enzymes, and an acyl protein carrier in the fatty acid synthase complex.
  • Vitamin B6 (Pyridoxine) – Vitamin B6, in the form of PLP, is a coenzyme for over 100 enzymes involved in amino acid metabolism. PLP is a coenzyme for aminotransferases, decarboxylases, racemases, and dehydratases. PLP is a coenzyme in the first step of heme biosynthesis and the transsulfuration of homocysteine to cysteine.
  • Vitamin B7 (Biotin) – Biotin functions in metabolism as a coenzyme for transferring single-carbon units in the form of carbon dioxide for the following carboxylases: pyruvate carboxylase, propionyl-CoA carboxylase, acetyl-CoA carboxylase, and β-methylcrotonyl-CoA carboxylase. These enzymes play roles in gluconeogenesis, citric acid cycle, fatty acid synthesis, and leucine degradation.
  • Vitamin B9 (Folate)  – Folate functions in nucleic and amino acid metabolism as a coenzyme in single-carbon transfers. Folate functions as a coenzyme in nucleic acid metabolism in the processes of DNA synthesis in purine and pyrimidine nucleotide biosynthesis.  Folate functions as a coenzyme in amino acid metabolism in amino acid interconversions, including the conversion of homocysteine to methionine, which serves as the major source of methionine for the formation of the major methylating agent S-adenosyl-methionine.
  • Vitamin B12 (Cobalamin)  – Cobalamin functions as a coenzyme for two enzymes in human metabolism: methionine synthase and L-methylmalonyl-CoA mutase. Vitamin B12, in the form of methylcobalamin, is required as a coenzyme to methionine synthase for the methyl transfer reaction from methyltetrahydrofolate to homocysteine resulting in the formation of methionine and tetrahydrofolate. Vitamin B12, in the form of adenosylcobalamin, is required as a coenzyme to  L-methylmalonyl-CoA mutase in the isomerization reaction that results in the conversion of L-methylmalonyl-CoA to succinyl-CoA.
  • Vitamin C (Ascorbic Acid) – Vitamin C, in the form of ascorbate, has both enzymatic and nonenzymatic functions in the body. Ascorbate functions as a coenzyme as a reducing agent in the synthesis reactions of collagen, carnitine, neurotransmitters, and tyrosine. Ascorbate functions nonenzymatically as a powerful water-soluble antioxidant with the ability to reduce free radicals and reactive oxygen species. Ascorbate notably reduces glutathione radicals produced by the electron transport chain.
  • Vitamin A (Retinol) – Vitamin A functions metabolically in vision, cellular differentiation, gene expression, growth, immune system, and reproduction. In the form of 11-cis-retinal, Vitamin A is the chromophore group of rhodopsin found in the rod cells of the retina and is essential for night vision. In the form of retinoic acid, Vitamin A is required for the differentiation of certain cells like keratinocytes to epidermal cells and squamous epithelial keratinizing cells to mucous-secreting cells. Vitamin A can regulate gene expression by acting as transcription factors when bound to RAR and RXR. Vitamin A protects against xerophthalmia by maintaining normal growth of the conjunctival membranes of the eye. Vitamin A plays roles in processes involved in innate and adaptive immunity, including cell differentiation and hematopoiesis. Vitamin A plays a vital role in spermatogenesis in reproduction.
  • Vitamin D (Cholecalciferol) – Vitamin D, in its active form 1,25-(OH)2 vitamin D3, can function as a hormone by binding to receptors on target tissues to activate a signal transduction pathway and a regulator of gene expression by binding to a nuclear receptor to affect transcription. One of the most important functions of 1,25-(OH)2 vitamin D3 is to work with parathyroid hormone to maintain blood calcium homeostasis. 1,25-(OH)2 vitamin D3 functions to increase the absorption of calcium in the small intestine and reabsorption of calcium in the kidneys in response to low blood calcium. It also works with parathyroid hormone to stimulate the resorption of calcium from the bone to increase blood calcium levels. 1,25-(OH)2 vitamin D3 can also bind to various nuclear vitamin D receptors, or VDRs, in the bones, intestines, kidneys, and skin to stimulate the transcription of genes. This process is key to osteoclast maturation.
  • Vitamin E (Tocopherol) – Vitamin E is best known to function as a chain-breaking antioxidant that neutralizes the lipid peroxyl radicals during lipid peroxidation to prevent cyclic propagation of lipid peroxidation. This process is key in protecting the polyunsaturated fatty acids within the phospholipids of plasma membranes and plasma lipoproteins.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K mainly functions in the synthesis of several blood coagulation factors. It also plays a role in bone mineralization. Vitamin K performs these functions by enabling the carboxylation of glutamic acid residues in proteins to form γ-glutamic carboxyl (Gla) residues. Gla residues enable proteins to bind with calcium and interact with other proteins, which is necessary for blood coagulation and bone mineralization.
  • Calcium – 99% of the calcium in the body is in bone and teeth as a structural component. The remaining calcium in the body is found in intracellular and extracellular spaces and plays key roles in innervation, muscle contraction, blood coagulation, hormone secretion, and intracellular adhesion.
  • Magnesium – Magnesium is an important intracellular cation for numerous functions throughout the body. Magnesium plays a key role in metabolic reactions such as energy storage, glucose metabolism, and nucleic acid and protein synthesis. Magnesium also functions in oxidative reactions, immune function, and bone development. Magnesium plays a role in stabilizing excitable membranes by maintaining electrolyte balance and homeostasis of calcium, sodium, and potassium. Magnesium acts as a calcium channel antagonist and plays a role in vasodilation.
  • Phosphorus – Phosphorus has various structural and metabolic functions throughout the body. Structurally, phosphorus functions to form the structure of bone and teeth along with calcium, the phosphate backbone of DNA and RNA, and the phospholipid bilayer of cell membranes. Metabolically, phosphorus functions to create and store energy in phosphate bonds of ATP, regulate acid/base balance in the blood as a buffer, regulate gene transcription, regulate enzyme activity, and enable signal transduction of numerous regulatory pathways.
  • Sodium – As an extracellular cation, sodium functions to regulate blood volume, blood pressure, osmotic equilibrium, and pH. Sodium and potassium ions function together to create an action potential maintained by ion pumps that allow for neurotransmission, muscle contraction, and heart function. Sodium also plays a critical role in the transport of nutrients across the plasma membrane.
  • Potassium – Potassium is critical for normal cellular function. Sodium and potassium ions function together to create an action potential maintained by Na+-K+ ATPase, allowing for neurotransmission, muscle contraction, and heart function. Potassium also works alongside sodium to maintain intracellular and extracellular osmotic pressure.
  • Chloride – As the most important extracellular anion in the body, chloride functions to maintain fluid balance, acid-base balance, electrolyte balance, electrical neutrality, and muscle function throughout the body. Chloride works with sodium to maintain fluid balance. Chloride also works with bicarbonate to maintain acid-base balance.
  • Iron – Iron’s functions are essential for oxygen transport and cell proliferation—iron functions as the core of heme proteins like myoglobin, hemoglobin, and cytochromes. Myoglobin and hemoglobin are essential for oxygen storage and transport, while cytochromes are essential for electron transport chain reactions in energy metabolism. Iron is also critical in its nonheme form in iron-sulfur enzymes like succinate dehydrogenase and NADH dehydrogenase in oxidative metabolism.
  • Zinc – Zinc functions structurally as a component of proteins and catalytically as a component of >300 enzymes in the body. Zinc’s functions are pervasive throughout the body and crucial to growth, immunity, cognitive function, and bone health.
  • Copper – Copper functions as a critical cofactor to a group of cellular transporters called cuproenzymes. Copper is essential for the proper function of human organs and metabolic processes such as hemoglobin synthesis, neurotransmitter synthesis, iron oxidation, cellular respiration, antioxidant peptide amidation, pigment formation, and connective tissue formation.
  • Iodine – The primary function of iodine is its role in the synthesis of thyroid hormones thyroxine (T4) and triiodothyronine (T3). At the apical surface of the thyrocyte, iodide is oxidized by the enzymes thyroperoxidase (TPO) and hydrogen peroxide to attach it to tyrosyl residues on thyroglobulin to produce the precursors of thyroid hormones: monoiodotyrosine (MIT) and diiodotyrosine (DIT). TPO then catalyzes the formation of a diether bridge between the phenyl groups of iodotyrosine to create thyroid hormones. The linkage of two DITs produces T4, while the linkage of MIT and DIT produces T3. T3 and T4  are almost structurally identical, but T3 has one less iodine than T4. Thyroid hormones function to regulate fetal cell growth, postnatal growth, and basal metabolic rate.
  • Selenium – Selenium functions as an essential component of selenoproteins that play major roles in dense against oxidation, thyroid hormone formation, DNA synthesis, reproduction, and fertility. The functions of most selenoproteins are unknown, but the known functions involve participation in antioxidant and anabolic processes. A family of antioxidant enzymes named glutathione peroxidases is dependent upon selenium to function to neutralize hydrogen peroxide and organic hyperoxides in both intracellular and extracellular compartments. Deiodinases are a group of three selenoenzymes responsible for converting T4 to T3 in thyroid hormone activation. Selenoprotein-P is the most abundant selenoprotein found in plasma and plays a major role in the transport and homeostasis of selenium in tissues.

Testing

Carbohydrates

Measuring the amount of glucose in plasma is one of the most important ways to screen for and manage diabetes. To clinically test and monitor blood glucose, blood is drawn from a vein, usually when the patient has fasted for at least 8 hours. The level of glucose is measured in milligrams of glucose per deciliter plasma. A healthy fasting blood glucose level is less than or equal to 99 mg/dL. Someone who has an increased risk for diabetes, or prediabetes, falls in the range of fasting blood glucose of 100 to 125 mg/dL. If a patient has a fasting blood glucose of 126 mg/dL or greater on two separate occasions, they can receive a diagnosis of diabetes.

Proteins

Nitrogen balance is the gold standard for testing the protein status of the body. Nitrogen balance can serve as a marker of adequate nutrition and physiological stress. Nitrogen balance is equal to the grams of nitrogen consumed minus the grams of nitrogen excreted. The grams of nitrogen consumed is calculated by the grams of protein consumed divided by 6.25 grams of protein per 1 gram of nitrogen. The grams of nitrogen excreted is calculated by extrapolating losses with grams of nitrogen in urinary urea plus 4 grams, which accounts for losses in feces, sweat, skin, and wounds. Under normal conditions, an individual should be at nitrogen equilibrium, or nitrogen balance equals zero. Critically ill patients often have negative nitrogen, so the goal with them is to increase the protein intake to achieve a positive nitrogen balance for healing.

Lipids

To test the amount of lipids in the body, a sample of blood is taken via venipuncture in tubes and analyzed for serum or plasma total cholesterol, triglycerides, and lipoproteins. Cholesterol levels remain fairly constant so that sampling is possible at any time. In contrast to cholesterol levels, triglyceride levels fluctuate throughout the day, so blood collection should occur after a 12-hour fasting period because, at that point, chylomicrons should have cleared from the circulation. To separate and quantify lipoproteins from the plasma sample, ultracentrifugation, precipitation, and electrophoresis are performed. High vs. low plasma lipid levels are determined based on the bell-shaped distribution of the general population. Cholesterol levels are determined based on the risk for coronary atherosclerosis. Cholesterol levels below 200 mg/dl are considered desirable, levels from 200 to 239 mg/dl are considered borderline high cholesterol, and levels of 240 mg/dl or greater are considered high cholesterol.

  • Vitamin B1 (Thiamin) – Thiamin status is measurable via urinary thiamin excretion, erythrocyte thiamin, and erythrocyte transketolase activity. Erythrocyte transketolase activity is considered the gold standard functional test of thiamin status.
  • Vitamin B2 (Riboflavin) – Riboflavin status is measured via erythrocyte glutathione reductase activity, erythrocyte flavin, and urinary flavin. Erythrocyte glutathione reductase activity is the most common method to determine riboflavin status.
  • Vitamin B3 (Niacin) – Niacin status can be measured using urinary 1-methyl nicotinamide excretion, plasma concentrations of 2-pyridone, erythrocyte pyridine nucleotides, and transfer of adenosine diphosphate ribose as a functional measurement. Urinary 1-methyl nicotinamide is the most reliable and sensitive measure of niacin status.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid status can be measured using urinary pantothenic acid excretion and whole blood pantothenic acid concentration.
  • Vitamin B6 (Pyridoxine)  – Vitamin B6 status assessment is best with plasma PLP. A plasma PLP of <20 nmol/L indicates a vitamin B6 deficiency.
  • Vitamin B7 (Biotin) – Biotin status is measurable with urinary biotin and 3-hydroxyisovalerate excretion. Decreased urinary excretion of biotin along with increased urinary excretion of 3-hydroxyisovalerate indicates biotin deficiency.
  • Vitamin B9 (Folate)  – The primary test used to measure folate status is erythrocyte folate. Given folate is taken up by developing erythrocytes in the bone marrow, erythrocyte folate concentration is an ideal indicator of long-term folate status. Plasma homocysteine can also be useful as an indicator of folate status given in inadequate quantities of folate; not as much homocysteine can undergo conversion to methionine. Serum folate can also be tested as an indicator of dietary folate intake but is limited and should be used in conjunction with additional folate status indicators.
  • Vitamin B12 (Cobalamin)  – The primary test to measure vitamin B12 status is serum vitamin B12, reflecting both intake and stores. The lower limit of serum vitamin B12 for adults is 170 to 250 pg/mL. Serum methylmalonic acid concentration is another specific and functional indicator of vitamin B12 status because serum methylmalonic acid concentrations become elevated during vitamin B12 deficiency. Serum total homocysteine concentration is a functional but non-specific indicator of vitamin B12 status due to elevation during vitamin B12 deficiency.
  • Vitamin C (Ascorbic Acid – Vitamin C status testing is via plasma vitamin C and leukocyte vitamin C. Plasma vitamin C concentration is sensitive to a recent diet, while leukocyte vitamin C reflects tissue stores. A plasma vitamin C concentration of less than 0.2 mg/dL is considered deficient.
  • Vitamin A (Retinol) – The gold standard for testing vitamin A status is through a liver biopsy because the liver is vitamin A’s major storage organ. However, this measure is not very feasible in humans. Retinol status is testable with plasma retinol concentration, but it only indicates low status if there is a severe deficiency. Vitamin A status may also be tested with a relative dose-response test, which measures the magnitude of increased RBP following supplementation.
  • Vitamin D (Cholecalciferol) – Vitamin D status is tested by using serum 25-hydroxyvitamin D concentrations. A serum 25-hydroxyvitamin D concentration that is less than 20 ng/mL represents a vitamin D deficiency and a need for supplementation.
  • Vitamin E (Tocopherol) – Vitamin E status is difficult to test because serum concentrations of vitamin E are largely age-dependent and are influenced by blood lipids. In the general population, α-tocopherol plasma levels can range from 19.9 micromoles/L to 34.2 micromoles. More research needs to be done to adjust specific requirements to an individual’s bioavailability.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K status is difficult to assess due to its being lipophilic and not very abundant. However, functional tests such as prothrombin time or Gla protein measurement can be useful to assess vitamin K status indirectly.
  • Calcium – Calcium status is difficult to assess in individuals because there is no reliable indicator that can establish a relationship between calcium and a particular disease state. Total body calcium is not useful to assess calcium intake because the body regulates calcium in a very tight range and will adapt to conserve it. Bone-mass measurements may indicate long-term calcium status by assessing changes in bone density.
  • Magnesium – Magnesium status can be tested with serum magnesium. Serum magnesium is maintained at a tight range of 1.7 to 2.6 mg/dL. A serum value of under 1.7 mg indicates a magnesium deficiency. A serum value of over 2.6 mg/dL indicates magnesium toxicity.
  • Phosphorus – Serum phosphorus is the most common way to assess phosphorus status. Serum phosphorus is maintained in a relatively narrow range of 2.5 to 4.5 mg/dL. Although serum phosphorus does not reflect the full body stores, serum phosphorus is crucial for various cellular processes in the body. Serum phosphorus below or above the normal range can indicate a deficiency and toxicity, respectively.
  • Sodium – Sodium balance is tested via plasma sodium concentration. A plasma sodium concentration greater than 150 mmol/L indicates sodium toxicity or hypernatremia. A plasma sodium concentration of less than 136 mmol/L indicates sodium deficiency or hyponatremia.
  • Potassium – Potassium balance is tested via serum potassium. The body maintains normal serum potassium levels in a narrow range of 3.5 to 5.5 mmol/L. Potassium toxicity, or hyperkalemia, occurs at serum potassium concentrations greater than 5.5 mmol/L. Potassium deficiency, or hypokalemia, occurs at concentrations less than 3.5 mmol/L.
  • Chloride – Since chloride serves as an important diagnostic indicator for various diseases, it can be tested for in serum, sweat, urine, and feces. Serum and urine chloride concentrations are used in the diagnosis of acid-base and osmolar disorders and used in formulas like the anion gap, strong anion gap, strong ion difference, and chloride/sodium ratio. Sweat chloride concentration is used in the diagnosis of cystic fibrosis when it is above 60 mmol/L.
  • Iron  – Iron is tested via serum-based indicators of iron status, such as hemoglobin, plasma ferritin, and plasma transferrin saturation. Hemoglobin is routinely measured to indicate anemia but is not specific for iron. Plasma ferritin is the gold standard of iron status because it is the most specific indicator of iron stores. A plasma ferritin concentration of less than 20 ng/L indicates iron deficiency. High plasma ferritin values can indicate iron overload. Transferrin saturation indicates the ratio of iron to transferrin to reflect transport iron. Transferrin saturation is low-cost but shows a pronounced diurnal variation.
  • Zinc – Zinc status testing is via serum zinc. A concentration of zinc below the lower value of the reference range of 10 to 18 micromol/L is considered a deficiency.
  • Copper – Copper status evaluation is via serum copper or serum ceruloplasmin. A concentration of serum copper below the lower value of the reference range of 12 to 20 micromol/L is considered a deficiency.
  • Iodine – Iodine status can be assessed with four different methods: urinary iodine concentration, goiter rate, serum TSH, and serum Tg. Urinary iodine, serum Tg, and goiter rate are complementary tests given urinary iodine are sensitive to recent iodine intake in a matter of days, serum Tg shows an intermediate response in a matter of weeks or months, and goiter rate changes reflect iodine nutrition in a matter of months or years. TSH can be used to assess iodine status reflecting on the level of circulating thyroid hormone but is a relatively insensitive indicator of iodine status in adults. However, TSH is a sensitive indicator of iodine status in newborns.
  • Selenium – Selenium status is tested via serum selenium. A concentration of selenium below the lower value of the reference range of 0.75 to 1.85 micromol/L is considered a deficiency.

Clinical Significance

Carbohydrates

Diabetes refers to a group of metabolic diseases of disordered glucose metabolism. Diabetes is characterized by hyperglycemia, or high blood sugar, and premature vascular disease. Symptoms of diabetes-related hyperglycemia include polydipsia, polyuria, weight loss, polyphagia, and blurred vision. Acute and life-threatening complications of uncontrolled diabetes include hyperglycemia with diabetic ketoacidosis or nonketotic hyperosmolar syndrome. Long-term complications of uncontrolled diabetes include macrovascular and microvascular complications that lead to loss of vision, renal failure, neuropathy, and cardiovascular disease. There are three types of diabetes: type 1, type 2, and gestational. Type 1 diabetes occurs in 5 to 10% of cases and is characterized by absolute insulin deficiency and pancreatic beta-cell destruction. Insulin is a hormone produced by pancreatic beta cells that stimulate sugar uptake in the blood by cells. Insulin therapy is required to treat type 1 diabetes. Type 2 diabetes occurs in 90 to 95% of cases and is characterized by insulin resistance and impaired beta-cell function. In some individuals with type 2 diabetes, blood glucose control can be managed with lifestyle changes like diet, weight reduction, and exercise, and/or oral glucose-lowering medications. However, some individuals may need insulin therapy. Gestational diabetes occurs in 9% of pregnant women during the second or third trimester of pregnancy. Glucose tolerance usually returns to normal after delivery, but this increases the risk for type 2 diabetes later in life.

Proteins

Protein-energy malnutrition is a problem for children in developing and developed countries around the world and contributes to acute and chronic childhood illness. In cases of extreme protein-energy malnutrition, marasmus and kwashiorkor are the two main clinical syndromes seen. Marasmus is more common and is characterized by muscle wasting and depletion of subcutaneous fat stores without edema as a result of deprivation of calories and nutrients. In addition, there is poor growth, little disease resistance, slowed metabolism, and impaired brain development. This usually occurs in children under the age of 5 due to their increased caloric requirements. Kwashiorkor is characterized by normal weight with edema, poor growth, low blood albumin, little disease resistance, and apathy resulting from a diet with an adequate caloric intake but inadequate protein. This commonly occurs in older infants or toddlers who are displaced from breastfeeding due to the birth of a younger sibling and have to wean rapidly but are unable to increase protein intake enough.

Lipids

Lipids in abnormal concentrations attract clinical attention. Abnormal lipid levels can occur due to abnormalities in the synthesis, degradation, and transport of lipoprotein particles. Hyperlipidemia is defined as elevated levels of lipids or lipoproteins in the blood. Hyperlipidemia is very clinically relevant due to its association with an increased risk of atherosclerotic cardiovascular disease. Other clinical manifestations of hyperlipidemia include ischemic vascular disease, acute pancreatitis, and visible accumulations of lipid deposits. Increased plasma lipid levels can be related to genetic disorders, dietary factors, certain drugs, and as a secondary symptom of certain diseases.

Vitamin B1 (Thiamin)

Thiamin deficiency is historically known as a disease called beriberi. Currently, in developed nations, thiamin deficiency mainly occurs with chronic alcoholism and is called Wernicke-Korsakoff syndrome. Symptoms of thiamin deficiency are nonspecific and include anorexia, weight loss, apathy, short-term memory issues, confusion, irritability, muscular weakness, and enlargement of the heart.

Vitamin B2 (Riboflavin)

The symptoms of riboflavin deficiency include sore throat, angular stomatitis, glossitis, dermatitis, and weakness. It is rare but can occur with diseases such as cancer, diabetes, cardiac disease, and alcoholism.

Vitamin B3 (Niacin)

The classic clinical manifestation of severe niacin deficiency is a disease called pellagra. Pellagra is characterized by a symmetrical, pigmented rash that develops in sunlight exposed areas, GI symptoms such as vomiting, constipation, diarrhea, a bright red tongue, and neurological problems such as depression and fatigue, apathy, headache, and loss of memory. Pellagra was common in the United States and Europe in areas where corn was a dietary staple in the early twentieth century. Pellagra has disappeared from developed countries except for cases of chronic alcoholism. It persists in parts of India, China, and Africa.

Vitamin B5 (Pantothenic Acid)

Pantothenic acid deficiencies are extremely rare but have been shown in individuals fed diets devoid of pantothenic acid. Symptoms of deficiency include irritability, fatigue, apathy, sleep disturbances, GI complaints, numbness, paresthesias, muscle cramps, and hypoglycemia with increased insulin sensitivity.

Vitamin B6 (Pyridoxine) 

Vitamin B6 deficiency is rare in healthy individuals. Symptoms of vitamin B6 deficiency include seborrheic dermatitis, microcytic anemia, convulsions, and confusion. Microcytic anemia occurs due to PLP’s role as a cofactor in the first step in heme biosynthesis.

Vitamin B7 (Biotin)

Biotin deficiency is rare but can occur in specific scenarios. Biotin deficiency can occur in people who ingest raw eggs due to the protein avidin, which inhibits biotin absorption. It can also occur in people with genetic defects in the enzyme biotinidase. Symptoms of biotin deficiency include thinning of hair, loss of hair color, dermatitis, depression, lethargy, and hallucinations.

Vitamin B9 (Folate) 

Folate deficiency results in impaired synthesis of DNA and RNA, which can manifest clinically megaloblastic anemia and developmental disorders in utero. Megaloblastic or macrocytic anemia occurs when red blood cell development is halted in the early erythroblast stage due to a lack of folate, allowing DNA synthesis to continue and erythroblasts to divide and mature. Early erythroblasts are large and do not contain much hemoglobin. Inadequate maternal folate status during pregnancy can result in neural tube defects such as spina bifida and anencephaly. Neural tube defect risk reduction has been achieved with daily supplementation of 400 mcg of folate in women of childbearing age. In addition, there is some evidence that might suggest folate reduces the risk of cardiovascular disease, certain cancers, and psychiatric disorders.

Vitamin B12 (Cobalamin) 

The major cause of clinical effects of vitamin B12 deficiency is pernicious anemia, which is caused by a lack of functional intrinsic factor in the stomach due to autoimmune destruction of gastric parietal cells. Malabsorption of food-bound vitamin B12 can also occur due to non-autoimmune atrophic gastritis, which causes loss of stomach acid and mainly affects the elderly. The hematological effects of vitamin B12 deficiency are clinically indistinguishable from those of folate deficiency causing macrocytic, or megaloblastic, anemia. Vitamin B12 deficiency can also result in impaired neurological function and increased neural tube defect risk.

Vitamin C (Ascorbic Acid)

Vitamin C deficiency is clinically and historically known as scurvy. Vitamin C deficiency is currently rare and only seen in malnourished populations with chronic conditions, poor diet, malabsorption, or substance dependency. Symptoms of vitamin C deficiency include gingival inflammation, fatigue, petechiae, bruising, and joint pain.

Vitamin A (Retinol)

Vitamin A deficiency affects 20-40 million children worldwide in regions with low-fat, plant-based diets and protein-calorie malnutrition. Vitamin A deficiency more commonly causes death than blindness in children in high-risk regions due to its role in the immune system. Vitamin A deficiency can also cause an increased risk of respiratory and diarrheal infections, decreased growth rate, slow bone development, and decreased survival from a serious illness.

Vitamin D (Cholecalciferol)

Vitamin D deficiency can lead to rickets and osteomalacia due to its critical role in bone and mineral metabolism. Rickets occurs in infants and children as a result of the failure of the bone to mineralize. The symptoms of rickets include growth retardation and bowing of the long bones of the legs. Osteomalacia occurs in adults; as a result, inadequate amounts of calcium and phosphate causing demineralization of the bone. Vitamin D may have extraskeletal effects and play a role in cardiovascular diseases, autoimmune diseases, neurological diseases, cancer, asthma, and pregnancy complications.

Vitamin E (Tocopherol)

Vitamin E deficiency is very rare but can occur in certain individuals. Symptoms of vitamin E deficiency include oxidative damage of tissues, membrane damage of cells, neurological abnormalities such as peripheral neuropathy, muscular, functional abnormalities like ataxia, and hemolytic anemia. Vitamin E deficiency most commonly occurs in premature babies of very low birthweight, people with fat-malabsorption disorders like Crohn’s disease and cystic fibrosis, and those who have a rare neurodegenerative disease called ataxia with vitamin E deficiency (AVED) that is caused by mutations in the gene for αβ-tocopherol transfer protein.

Vitamin K (Phylloquinone; Menaquinone)

Vitamin K deficiency is uncommon in healthy adults but may be seen in those with gastrointestinal malabsorptive disorders. However, newborns are at high risk for vitamin K deficiency. Newborns are at risk given milk is low in vitamin K, their stores are low since vitamin K does not pass the placenta, and their intestines are not yet populated with vitamin K synthesizing bacteria. Infants born in the United States and Canada routinely receive 0.5 to 1 mg of intramuscular phylloquinone within 6 hours of birth to prevent vitamin K deficiency bleeding, or VKDB. VKDB can affect infants up to 3 to 4 months of age and cause intracranial hemorrhage, central nervous system damage, and liver damage.

Calcium

Hypocalcemia, or calcium deficiency, can result from inadequate calcium intake, poor calcium absorption, or excessive calcium losses. Poor calcium absorption can occur due to inadequate vitamin D status. Excessive calcium losses can occur due to a lack of PTH. Symptoms of hypocalcemia can include muscle spasms, cramps, paresthesia, tetany, and seizures. Long-term hypocalcemia can impact bone health and result in reduced bone mass and osteoporosis. Hypercalcemia can occur due to increased bone resorption, increased intestinal absorption, and decreased renal excretion of calcium. Syndromes that increase PTH production can result in excessive calcium reabsorption and calcitriol production in the kidney. Excess PTH and calcitriol production can result in increased bone resorption. Excess calcitriol also can increase intestinal absorption. Symptoms of hypercalcemia include fatigue, confusion, polydipsia, frequent urination, upset stomach, bone pain, muscle weakness, and cardiac arrhythmia.

Magnesium

Magnesium deficiency, or hypomagnesemia, can occur due to chronic inadequate magnesium intake, chronic diarrhea, magnesium malabsorption, alcoholism, and medications like diuretics, antacids, proton pump inhibitors, and aminoglycoside antibiotics. Symptoms of hypomagnesemia are nonspecific and include muscle weakness, cramps, spasms, and tremors. Magnesium toxicity, or hypermagnesemia, can occur with supplemental magnesium, especially in intestinal or renal disease. Symptoms of hypermagnesemia include diarrhea, nausea, vomiting, headaches, lethargy, and flushing. At very high serum concentrations of magnesium, cardiac and electrocardiogram changes can occur, as well as coma, respiratory depression, and cardiac arrest.

Phosphorus

Phosphorus deficiency, or hypophosphatemia, is relatively rare in healthy individuals. However, hypophosphatemia can occur due to conditions that cause a shift of phosphorous from extracellular fluid to intracellular fluid, decreased intestinal absorption of phosphorus, or increased renal excretion of phosphorus. Hypophosphatemia may also occur in individuals with rare genetic disorders that decrease renal reabsorption and increase phosphorus excretion. Hypophosphatemia can appear asymptomatic until serum levels reach <1.5 mg/dL, where symptoms of anorexia, confusion, seizures, and paralysis can present. Respiratory depression can occur at serum levels <1 mg/dL. Treatment of hypophosphatemia includes oral or intravenous supplementation, depending on the severity of deficiency. Phosphorus toxicity, or hyperphosphatemia, can occur in those with chronic kidney disease due to decreased phosphorus excretion. Hyperphosphatemia is associated with increased death from cardiovascular disease due to vascular calcification in individuals with and without chronic kidney disease. Hyperphosphatemia is treated first by dietary restriction of phosphate, protein restriction, and dialysis if the latter fails. Hyperphosphatemia can also be treated with oral phosphate binders that block dietary phosphorus absorption.

Sodium

Given the pervasiveness of sodium in various foods, sodium deficiency is highly unlikely in healthy individuals. Sodium deficiency, or hyponatremia, can only occur in pathological conditions such as adrenal insufficiency, kidney disease that results in excessive sodium losses, excessive burns, diabetic ketoacidosis, and additional conditions that cause excessive sodium losses such as vomiting, diarrhea, prolonged sweating, and excessive diuretic use. Symptoms of hyponatremia include hypovalemia, lethargy, confusion, and weakness. Sodium toxicity, or hypernatremia, can occur with dehydration, hyperaldosteronemia, and renal failure. Symptoms of hypernatremia include hypervolemia, hypertension, convulsions, or coma. Even under normal conditions, continuous excessive intake of sodium can result in hypertension in certain individuals.

Potassium

Potassium is considered to be a shortfall nutrient in the American diet according to the 2010 Dietary Guidelines for American’s Advisory Committee because most Americans are unable to consume the AI of 4,700 mg/day. There is moderate evidence of an association between blood pressure reduction and potassium intake in adults, which influences cardiovascular disease risk. Hypokalemia usually occurs due to inadequate potassium intake and/or excessive potassium losses. Hypokalemia can clinically manifest in symptoms such as muscle weakness, smooth muscle dysfunction, cardiac complications, and glucose intolerance. Hyperkalemia usually occurs due to impaired renal excretion. Hyperkalemia will manifest in excitatory tissues and present symptoms such as neuromuscular symptoms such as paresthesias and fasciculations, cardiac arrest, and impaired renal function.

Chloride

Hypochloremia, or chloride deficiency, is related to clinical situations that cause excessive chloride losses due to gastrointestinal or renal conditions such as vomiting and renal failure. When serum chloride levels fall, bicarbonate reabsorption increases proportionately, resulting in metabolic alkalosis. Symptoms of hypochloremia are concurrent with those of metabolic alkalosis and include confusion, apathy, cardiac arrhythmias, and neuromuscular irritability. Hyperchloremia, or chloride toxicity, is related to clinical situations that cause excessive gastrointestinal or renal bicarbonate losses, such as severe diarrhea and medications that promote bicarbonate excretion. When serum bicarbonate levels fall, chloride reabsorption increases proportionately, resulting in metabolic acidosis.

Iron

The World Health Organization (WHO) indicates iron deficiency to be the most common form of malnutrition globally, affecting 25% of the global population. Iron deficiency is highly prevalent in both developing and developed countries. Iron deficiency is most commonly caused by inadequate dietary iron intake, inadequate iron utilization due to diseases, impaired iron absorption, or excess iron loss. Iron deficiency can often be avoided and reversed with iron supplementation and/or reducing iron losses. Untreated iron deficiency can result in microcytic anemia, poor cognitive performance, impaired immune function, impaired growth in children, poor pregnancy outcomes, and reduced endurance capacity. On the other hand, iron overload can be caused by a disease called hereditary hemochromatosis due to a C282Y mutation in the HFE gene. Hereditary hemochromatosis can be treated with iron removal therapy.

Zinc

Zinc deficiency can present clinically with symptoms such as dermatitis, alopecia, decreased appetite, frequent diarrhea, frequent upper respiratory infection, stunted growth in children, and hypogonadism. Zinc deficiency can occur due to diarrheal illness, kidney failure, and genetic diseases acrodermatitis enteropathica (AE). AE is a fatal disease of zinc malabsorption due to a mutation in the ZIP4 gene, which encodes the major intestinal zinc uptake protein. AE is treated with lifelong zinc supplementation of 100 mg/kg per day. Zinc toxicity is rare due to the tight regulation of zinc concentrations in the body. However, long-term zinc supplementation above the tolerable upper intake level of 40 mg/day can decrease copper absorption and cause copper deficiency. This occurs because zinc induced the formation of the intestinal cell protein metallothionein, which binds to metals and prevents their absorption by trapping them in the intestinal cell. Metallothionein has a stronger affinity for copper than zinc, thus trapping copper in the intestinal cell and halting absorption.

Copper

Copper deficiency generally manifests in systems such as bone marrow hematopoiesis, optic nerve function, and the nervous system. Copper deficiency causes symptoms such as fatigue and weakness. Copper deficiency can occur due to excessive zinc supplementation and the genetic disorder of copper malabsorption called Menkes disease. Menkes disease is caused by a mutation in the ATP7A gene, which causes copper to accumulate in the enterocyte, making it unable to reach the blood or any other organ system. Another genetic disease of copper metabolism is Wilson disease, which is a genetic disease of accumulation of copper mainly in the liver and the brain due to a mutation in the ATP7B gene responsible for the ATP7B exporter.

Iodine

Iodine deficiency will cause a compensatory response of the thyroid gland. When iodine intake falls below approximately 100 mcg/day, the pituitary increases secretion of TSH, which increases plasma iodine clearance by the thyroid. Thus, plasma iodine levels decrease, and thyroid hormone synthesis decreases, resulting in hypothyroidism. The increase in TSH also increases the thyroid cell number and cell size resulting in an enlarged thyroid gland or goiter. The goiter can be treated with iodine supplementation, gradually reducing the size or a thyroidectomy. If left untreated, the goiter may cause tracheal and esophageal pressure. Thyroid deficiency during pregnancy can lead to neurological cretinism in the offspring.

Selenium

Selenium deficiency has been known to appear in humans after severe and prolonged cases of selenium deprivation. Selenium deficiency is known as Keshan disease and occurs in areas where selenium content in the soil is low, like China. Symptoms of Keshan disease include cardiomyopathy, peripheral myopathy, decreased muscle tone and function, hair thinning, opacification of nails, and anemia.

References

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Nutrition – Types, Mechanism, Functions, Health Benefits

Nutrition are chemical substances required by the body to sustain basic functions and are optimally obtained by eating a balanced diet. There are six major classes of nutrients essential for human health: carbohydrates, lipids, proteins, vitamins, minerals, and water. Carbohydrates, lipids, and proteins are considered macronutrients and serve as a source of energy. Water is required in large amounts but does not yield energy. Vitamins and minerals are considered micronutrients and play essential roles in metabolism. Vitamins are organic micronutrients classified as either water-soluble or fat-soluble. The essential water-soluble vitamins include vitamins B1, B2, B3, B5, B6, B7, B9, B12, and C. The essential fat-soluble vitamins include vitamins A, E, D, and K. Minerals are inorganic micronutrients. Minerals can classify as macrominerals or microminerals. Macrominerals are required in amounts greater than 100 mg per day and include calcium, phosphorous, magnesium, sodium, potassium, and chloride. Sodium, potassium, and chloride are also electrolytes. Microminerals are those nutrients required in amounts less than 100 mg per day and include iron, copper, zinc, selenium, and iodine. This article will review the following biochemical aspects of the essential nutrients: fundamentals, cellular, molecular, function, testing, and clinical significance.

Digestive Systems and Nutrition

Animals use the organs of their digestive systems to extract important nutrients from food they consume, which can later be absorbed.

Key Points

Animals obtain lipids, proteins, carbohydrates, essential vitamins, and minerals from the food they consume.

The digestive system is composed of a series of organs, each with a specific, yet related function, that work to extract nutrients from food.

Organs of the digestive system include the mouth, esophagus, stomach, small intestine, and the large intestine.

Accessory organs, such as the liver and pancreas, secrete digestive juices into the gastrointestinal tract to assist with food breakdown.

Key Terms

  • digestion: the process, in the gastrointestinal tract, by which food is converted into substances that can be utilized by the body
  • macromolecule: a very large molecule, especially used in reference to large biological polymers (e.g. nucleic acids and proteins)
  • alimentary canal: the organs of a human or an animal through which food passes; the digestive tract

All living organisms need nutrients to survive. While plants can obtain the molecules required for cellular function through the process of photosynthesis, most animals obtain their nutrients by the consumption of other organisms. At the cellular level, the biological molecules necessary for animal function are amino acids, lipid molecules, nucleotides, and simple sugars. The food consumed consists of protein, fat, and complex carbohydrates, but the requirements of each are different for each animal.

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Balanced human diet: For humans, fruits and vegetables are important in maintaining a balanced diet. Both of these are an important source of vitamins and minerals, as well as carbohydrates, which are broken down through digestion for energy.

Animals must convert these macromolecules into the simple molecules required for maintaining cellular functions, such as assembling new molecules, cells, and tissues. The conversion of the food consumed to the nutrients required is a multi-step process involving digestion and absorption. During digestion, food particles are broken down to smaller components which will later be absorbed by the body.

Digestive System

The digestive system is one of the largest organ systems in the human body. It is responsible for processing ingested food and liquids. The cells of the human body all require a wide array of chemicals to support their metabolic activities, from organic nutrients used as fuel to the water that sustains life at the cellular level. The digestive system not only effectively chemically reduces the compounds in food into their fundamental building blocks, but also acts to retain water and excrete undigested materials. The functions of the digestive system can be summarized as follows: ingestion (eat food), digestion (breakdown of food), absorption (extraction of nutrients from the food), and defecation (removal of waste products).

The digestive system consists of a group of organs that form a closed tube-like structure called the gastrointestinal tract (GI tract) or the alimentary canal. For convenience, the GI tract is divided into upper GI tract and lower GI tract. The organs that make up the GI tract include the mouth, the esophagus, the stomach, the small intestine, and the large intestine. There are also several accessory organs that secrete various enzymes into the GI tract. These include the salivary glands, the liver, and the pancreas.

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Generalized animal digestive system: This diagram shows a generalized animal digestive system, detailing the different organs and their functions.

Challenges to Human Nutrition

One of the challenges in human nutrition is maintaining a balance between food intake, storage, and energy expenditure. Imbalances can have serious health consequences. For example, eating too much food while not expending much energy leads to obesity, which in turn will increase the risk of developing illnesses such as type-2 diabetes and cardiovascular disease. The recent rise in obesity and related diseases means that understanding the role of diet and nutrition in maintaining good health is more important than ever.

Carbohydrates: Sources, Uses in the Body, and Dietary Requirements

Carbohydrates, which break down to glucose, are a major source of energy for humans but are not essential nutrients.

Key Points

Carbohydrates include such items as fruits, grains, beans, and potatoes, along with sugars and sugared foods.

While fat is a better source of energy, the brain cannot burn fat and instead requires glucose.

Polysaccharides (complex carbs) are difficult for humans to break down but are useful as fiber to enhance the digestive process.

Government agencies recommend a dietary intake of 45–65% or 55–75% of carbohydrates to meet daily energy needs.

Of daily carbohydrate intake, only 10% should be simple carbs or sugars.

Key Terms

  • glucose: A simple monosaccharide (sugar) with a molecular formula of C6H12O6; it is a principle source of energy for cellular metabolism.
  • carbohydrate: A sugar, starch, or cellulose that is a food source of energy for an animal or plant; a saccharide.
  • saccharide: The unit structure of carbohydrates, of general formula CnH2nOn. Either the simple sugars or polymers such as starch and cellulose. The saccharides exist in either a ring or short chain conformation, and typically contain five or six carbon atoms.

EXAMPLES

Daily food intake that includes 8–10 fruit and vegetable servings (not starchy potatoes or grains, such as corn and rice) will not only provide plenty of energy but will also keep glucose levels in balance.

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Carbohydrates are a class of macromolecule: Grain products are rich sources of carbohydrates.

Foods high in carbohydrates include fruits, sweets, soft drinks, bread, pasta, beans, potatoes, bran, rice, and cereals. Carbohydrates are a common source of energy in living organisms, however, carbohydrate is not an essential nutrient in humans.

Carbohydrates are not necessary building blocks of other molecules, and the body can obtain all its energy from protein and fats. The brain and neurons generally cannot burn fat for energy but use solely glucose or ketones. Humans can synthesize some glucose (in a set of processes known as “gluconeogenesis”) from specific amino acids or from the glycerol backbone in triglycerides and, in some cases, from fatty acids. Carbohydrates and protein contain 4 kilocalories per gram, while fats contain 9 kilocalories per gram. In the case of protein, this is somewhat misleading as only some amino acids are able to undergo conversion into useful energy forms.

Organisms typically cannot metabolize all types of carbohydrates to yield energy. Glucose is a nearly universal and accessible source of calories. Many organisms also have the ability to metabolize other monosaccharides and disaccharides, though glucose is preferred. Polysaccharides are also common sources of energy. Even though these complex carbohydrates are not very digestible, they may comprise important dietary elements for humans. Called “dietary fiber,” these carbohydrates enhance digestion, among other benefits.

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Glucose Molecule: Image of a glucose molecule containing a fixed ratio of carbon, hydrogen and oxygen.

Based on the effects on risk of heart disease and obesity, the Institute of Medicine (IOM) recommends that American and Canadian adults get between 45–65% of dietary energy from carbohydrates. The Food and Agriculture Organization (FAO) and World Health Organization (WHO) jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).

Lipids: Sources, Uses in the Body, and Dietary Requirements

Fats store energy, facilitate absorption of fat-soluble vitamins, aid brain growth and development, and protect against many diseases.

Key Points

Vitamins A, D, E, and K should be taken with some dietary fat in order to facilitate their absorption and activity.

Humans cannot synthesize omega-6 and omega-3 fatty acids, so these fats must be obtained from the diet.

Omega-6 fatty acids are found in many foods, while omega-3 fatty acids are found in walnuts and are especially abundant in fatty fish.

Omega-3 fatty acids have many positive health benefits including reduced rates of cancer, cardiovascular disease, mental illness, and dementia.

Studies of dietary fat intake have found no link between the percentage of calories obtained from fats and the risk of cancer, heart disease, or obesity.

Trans fats, such as those present in partially hydrogenated vegetable oils, are a risk factor for cardiovascular disease.

Key Terms

  • phospholipids: Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers.
  • trans fats: Trans fats are unsaturated fats generated by physical agents such as heat or pressure that can lead to a variety of health problems.
  • fatty acid: Fatty acids can be saturated or unsaturated and are usually derived from triglycerides or phospholipids.

EXAMPLES

College students require optimal brain function, which is supported by fatty fish and walnuts.

Most of the fats found in food are triglycerides, cholesterol, and phospholipids. Some dietary fat is necessary for the absorption of fat-soluble vitamins (A, D, E, and K) and carotenoids. Humans and other mammals require fatty acids such as linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid), because they cannot be synthesized from simple precursors in the diet.

Both omega-6 and omega-3 are 18-carbon polyunsaturated fatty acids that differ in the number and position of their double bonds. Most vegetable oils (safflower, sunflower, and corn oils) are rich in linoleic acid. Alpha-linolenic acid is found in the green leaves of plants, selected seeds, nuts, and legumes, and particularly in flax, rapeseed, walnut, and soy. Fish oils are especially rich in the longer-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Numerous studies have shown that the consumption of omega-3 fatty acids has positive benefits in terms of infant development, cancer, cardiovascular disease, and mental illnesses such as depression, attention-deficit hyperactivity disorder, and dementia. In contrast, the consumption of trans fats, such as those present in partially hydrogenated vegetable oils, are now known to be a risk factor for cardiovascular disease.

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Omega-3 Fatty Acid: Docosahexaenoic acid (DHA) is an omega-3 fatty acid. It is essential for the proper functioning of the brain in both adults and infants. DHA concentrations in breast milk ranged from 0.07-1.0% of total fatty acids and are influenced by the amount of fatty fish in the mother’s diet. In the U.S., infant formula has been supplemented with DHA since 2001. Research suggests that DHA contributes to numerous nervous system functions such as visual acuity, neurogenesis, and synaptogenesis and that it lowers the risk for cardiovascular disease. It is highly concentrated in the brain and eye.

Several studies have suggested that total dietary fat intake is linked to obesity and diabetes. However, influential studies like the Women’s Health Initiative Dietary Modification Trial (an eight-year study of 49,000 women), as well as the Nurses’ Health Study and the Health Professionals Follow-up Study, have revealed no such link between the percentage of calories from fat and risk of cancer, heart disease, or weight gain. The Nutrition Source, a website maintained by the Department of Nutrition at the Harvard School of Public Health, summarizes the current evidence on the impact of dietary fat as follows: “Detailed research—much of it done at Harvard—shows that the total amount of fat in the diet isn’t really linked with weight or disease.”

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Salmon: Salmon is an excellent source of omega-3 fatty acids.

Proteins: Sources, Uses in the Body, and Dietary Requirements

Proteins are composed of 20 different amino acids, about half of which are essential, meaning they must be obtained from the diet.

Key Points

Protein-based foods (plant and animal) provide amino acids; however, the best source of essential amino acids is animal.

If the diet does not provide adequate protein, the body will obtain what it needs from itself, especially from its own muscles.

While adequate protein is required for building skeletal muscle and other tissues, there is ongoing debate regarding the use and necessity of high-protein diets in anaerobic exercise, in particular weight training and bodybuilding.

This use of protein as a fuel is particularly important under starvation conditions as it allows the body’s own proteins to be used to support life.

Key Terms

  • amino acid: Any of the twenty naturally occurring α-amino acids (having the amino, and carboxylic acid groups on the same carbon atom), and a variety of side chains, that combine, via peptide bonds, to form proteins.
  • denaturation: Denaturation is a process in which proteins or nucleic acids lose their tertiary and secondary structure which is present in their native state, by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), or heat.
  • protein: Any of numerous large, complex naturally-produced molecules composed of one or more long chains of amino acids, in which the amino acid groups are held together by peptide bonds.

Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals (including humans) must obtain some of the amino acids from the diet. The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids. Key enzymes that synthesize certain amino acids are not present in animals. One example is aspartokinase, which catalyzes the first step in the synthesis of lysine, methionine, and threonine from aspartate.

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Amino Acid: Ball-and-stick model of the cystine molecule, an amino acid formed from two cysteine molecules.

In animals, amino acids are obtained through the consumption of foods containing protein. Ingested proteins are then broken down into amino acids through digestion, which typically involves denaturation of the protein through exposure to acid and hydrolysis by enzymes called proteases. Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body’s own proteins to be used to support life, particularly those found in muscle. Amino acids are also an important dietary source of nitrogen.

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Protein: Muscle meat, such as steak, is an excellent source of the essential amino acids the body needs to create all necessary proteins.

A high-protein diet is often recommended by bodybuilders and nutritionists to help efforts to build muscle and lose fat. It should not be confused with low-carb diets, such as the Atkins Diet, which are not calorie-controlled and which often contain large amounts of fat. While adequate protein is required for building skeletal muscle and other tissues, there is ongoing debate regarding the use and necessity of high-protein diets in anaerobic exercise in particular weight training and bodybuilding. Extreme protein intake (in excess of 200g per day), coupled with an inadequate intake of other calorie sources (fat or carbohydrates), can cause a form of metabolic disturbance and death commonly known as rabbit starvation.

Relatively little evidence has been gathered regarding the effect of long-term high intake of protein on the development of chronic diseases. Increased load on the kidney is a result of an increase in the reabsorption of NaCl. This causes a decrease in the sensitivity of tubuloglomerular feedback, which, in turn, results in an increased glomerular filtration rate. This increases pressure in glomerular capillaries. When added to any additional renal disease, this may cause permanent glomerular damage.

Food Requirements and Essential Nutrients

Essential nutrients are those that cannot be created by an animal’s metabolism and need to be obtained from the diet.

Key Points

The animal diet needs to be well-balanced in order to ensure that all necessary vitamins and minerals are being obtained.

Vitamins are important for maintaining bodily health, making bones strong, and seeing in the dark.

Water-soluble vitamins are not stored by the body and need to be consumed more regularly than fat-soluble vitamins, which build up within body tissues.

Essential fatty acids need to be consumed through the diet and are important building blocks of cell membranes.

Nine of the 20 amino acids cannot be synthesized by the body and need to be obtained from the diet.

Key Terms

  • nutrient: a source of nourishment, such as food, that can be metabolized by an organism to give energy and build tissue
  • catabolism: destructive metabolism, usually including the release of energy and breakdown of materials
  • vitamin: any of a specific group of organic compounds essential in small quantities for healthy human growth, metabolism, development, and body function

Food Requirements

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A balanced diet: For humans, a balanced diet includes fruits, vegetables, grains, and protein. Each of these food sources provides different nutrients the body cannot make for itself. These include vitamins, omega 3 fatty acids, and some amino acids.

What are the fundamental requirements of the animal diet? The animal diet should be well balanced and provide nutrients required for bodily function along with the minerals and vitamins required for maintaining structure and regulation necessary for good health and reproductive capability.

Organic Precursors

The organic molecules required for building cellular material and tissues must come from food. Carbohydrates or sugars are the primary sources of organic carbons in the animal body. During digestion, digestible carbohydrates are ultimately broken down into glucose and used to provide energy through metabolic pathways. The excess sugars in the body are converted into glycogen and stored in the liver and muscles for later use. Glycogen stores are used to fuel prolonged exertions, such as long-distance running, and to provide energy during food shortages. Excess digestible carbohydrates are stored by mammals in order to survive famine and aid in mobility.

Another important requirement is that of nitrogen. Protein catabolism provides a source of organic nitrogen. Amino acids are the building blocks of proteins and protein breakdown provides amino acids that are used for cellular function. The carbon and nitrogen derived from these become the building block for nucleotides, nucleic acids, proteins, cells, and tissues. Excess nitrogen must be excreted, as it is toxic. Fats add flavor to food and promote a sense of satiety or fullness. Fatty foods are also significant sources of energy because one gram of fat contains nine calories. Fats are required in the diet to aid the absorption of fat-soluble vitamins and the production of fat-soluble hormones.

Essential Nutrients

While the animal body can synthesize many of the molecules required for function from the organic precursors, there are some nutrients that need to be consumed from food. These nutrients are termed essential nutrients: they must be eaten as the body cannot produce them.

Vitamins and minerals are substances found in the food we eat. Your body needs them to be able to work properly and for growth and development. Each vitamin has its own special role to play. For example, vitamin D (added to whole milk or naturally occurring in sardines), helps make bones strong, while vitamin A (found in carrots) helps with night vision. Vitamins fall into two categories: fat-soluble and water-soluble. The fat-soluble vitamins dissolve in fat and can be stored in your body, whereas the water-soluble vitamins need to dissolve in water before your body can absorb them; therefore, the body cannot store them.

Fat-soluble vitamins are found primarily in foods that contain fat and oil, such as animal fats, vegetable oils, dairy foods, liver, and fatty fish. Your body needs these vitamins every day to enable it to work properly. However, you do not need to eat foods containing these every day. If your body does not need these vitamins immediately, they will be stored in the liver and fat tissues for future use. This means that stores can build up; if you have more than you need, fat-soluble vitamins can become harmful. Some fat-soluble vitamins include vitamin A, vitamin K, vitamin D, and vitamin E. Unlike the other fat-soluble vitamins, vitamin D is difficult to obtain in adequate quantities in a normal diet; therefore, supplementation may be necessary.

Water-soluble vitamins are not stored in the body; therefore, you need to have them more frequently. If you have more then you need, the body rids itself of the extra vitamins during urination. Because the body does not store these vitamins, they are generally not harmful. Water-soluble vitamins are found in foods that include fruits, vegetables, and grains. Unlike fat-soluble vitamins, they can be destroyed by heat. This means that sometimes these vitamins can often be lost during cooking. This is why it is better to steam or grill these foods rather then boil them. Some water-soluble vitamins include vitamin B6, vitamin B12, vitamin C, biotin, folic acid, niacin, and riboflavin.

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Sea buckthorn seed oil: Sea buckthorn seed oil contains many vital nutrients.

The omega-3 alpha-linolenic acid and the omega-6 linoleic acid are essential fatty acids needed to synthesize some membrane phospholipids. Many people take supplements to ensure they are obtaining all the essential fatty acids they need. Sea buckthorn contains many of these fatty acids and is also high in vitamins. Sea buckthorn can be used to treat acne and promote weight loss and wound healing.

Minerals are inorganic essential nutrients that must also be obtained from food. Among their many functions, minerals help in cell structure and regulation; they are also considered co-factors. In addition to vitamins and minerals, certain amino acids must also be procured from food and cannot be synthesized by the body. These amino acids are the “essential” amino acids. The human body can synthesize only 11 of the 20 required amino acids. The rest must be obtained from food.

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Amino Acids: There are 20 known amino acids. Animals can make only 11, so the others must be obtained through the diet. Meats are the best source of amino acids, although some amino acids can also be obtained from vegetables and grains.

Fundamentals Nutrition

Carbohydrates

Carbohydrates are essential macronutrients that are the primary source of energy for humans; 1 gram of carbohydrate contains 4 kcal of energy. Carbohydrates also play roles in gut health and immune function. Carbohydrates are present in plant-based foods like grains, fruits, vegetables, and milk. Carbohydrates are ingested in the form of simple carbohydrates, like monosaccharides and disaccharides, or complex carbohydrates, like oligosaccharides and polysaccharides. Monosaccharides are the basic building blocks of all carbohydrates and include glucose, fructose, and galactose. Glucose is the primary form to which carbohydrates become metabolized in humans. Disaccharides contain two sugar units and include lactose, sucrose, and maltose. Lactose is a carbohydrate found in milk, and sucrose is basic table sugar. Oligosaccharides consist of 3 to 10 sugar units and include raffinose and stachyose, which are in legumes. Polysaccharides include greater than ten sugar units and consist of starches, glycogen, and fibers, like pectin and cellulose. Starches like amylose are in grains, starchy vegetables, and legumes and consist of glucose monomers. Glycogen is the storage form of glucose in animals and is present in the liver and muscle, but there is little to none in the diet. Fibers are plant polysaccharides like pectin and cellulose found in whole grains, fruits, vegetables, and legumes but are not digestible by humans. However, they play a major role in gut health and function and can be digested by microbiota in the large intestine. For healthy children and adults, carbohydrates should make up approximately 45 to 65% of energy intake based on the minimum required glucose for brain function. The recommended fiber intake is greater than 38 g for men and 25 g for women, which is the intake that research has observed to lower the risk of coronary artery disease. Some carbohydrates are more nutritious than others. Optimal carbohydrate intake consists of fiber-rich, nutrient-dense whole grains, fruits, vegetables, legumes, and added sugar.

Proteins

Proteins are essential macronutrients that contribute to structural and mechanical function, regulate processes in the cells and body, and provide energy if necessary. Proteins are composed of amino acids and are available in food sources like meats, dairy foods, legumes, vegetables, and grains. 1 gram of protein contains 4 kcal of energy. The recommended protein intake is 0.8 to 1 gram per kilogram of body weight per day. For healthy children ages 1 to 3, ages 4 to 18, and adults, approximately 5 to 20%, 10 to 30%, and 10 to 35% of daily energy intake should come from protein, respectively, based on the adequate amount needed for nitrogen equilibrium.

Lipids

Lipids are essential macronutrients that are the main source of stored energy in the body, contribute to cellular structure and function, regulate temperature, and protect body organs. Lipids are found in fats, oils, meats, dairy, and plants and consumed mostly in the form of triglycerides. One gram of fat contains 9 kcal of energy. For healthy children ages 1 to 3, ages 4 to 18, and adults, approximately 30 to 40%, 25 to 15%, and 20 to 35% of daily energy intake should come from fat, respectively. Approximately 5 to 10% and 0.6 to 1.2% of the daily fat energy intake should consist of n-6 polyunsaturated fatty acids (linoleic acid) and n-3 polyunsaturated fatty acids (α-linolenic acid), respectively.

Vitamin

  • Vitamin B1 (Thiamin) – Thiamin, or vitamin B1, is an essential water-soluble vitamin that acts as a coenzyme in carbohydrate and branched-chain amino acid metabolism. Thiamin is in food sources such as enriched and whole grains, legumes, and pork. The RDA (Recommended Dietary Allowance) of thiamin for adults is 1.1 mg/day for women and 1.2 mg/day for men.
  • Vitamin B2 (Riboflavin) – Riboflavin, or vitamin B2, is an essential water-soluble vitamin that acts as a coenzyme in redox reactions. Riboflavin is present in food sources such as enriched and whole grains, milk and dairy products, leafy vegetables, and beef. The RDA of riboflavin for adults is 1.1 mg/day for women and 1.3 mg/day for men.
  • Vitamin B3 (Niacin) – Niacin, or vitamin B3, is an essential water-soluble vitamin that acts as a coenzyme to dehydrogenase enzymes in the transfer of the hydride ion and an essential component of the electron carriers NAD and NADP. Niacin is present in enriched and whole grains and high protein foods like meat, milk, and eggs. The RDA of niacin for adults is 14 mg/day of NEs (niacin equivalents) for women and 16 mg/day of NEs for men.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid, or vitamin B5, is an essential water-soluble vitamin that acts as a key component of coenzyme A and phosphopantetheine, which are crucial to fatty acid metabolism. Pantothenic acid is widespread in foods. The AI (adequate intake) of pantothenic acid for adults is 5 mg/day.
  • Vitamin B6 (Pyridoxine)  – Vitamin B6, or pyridoxine, is an essential water-soluble vitamin that acts as a coenzyme for amino acid, glycogen, and sphingoid base metabolism. Vitamin B6 is widespread among food groups. The RDA for vitamin B6 for adults is 1.3 mg/day.
  • Vitamin B7 (Biotin) – Biotin, or vitamin B7, is an essential water-soluble vitamin that acts as a coenzyme in carboxylation reactions dependent on bicarbonate. Biotin is found widespread in foods, especially egg yolks, soybeans, and whole grains. The AI of biotin for adults is 30 mcg/day.
  • Vitamin B9 (Folate)  – Folate, or vitamin B9, is an essential water-soluble vitamin that acts as a coenzyme in single-carbon transfers in nucleic acid and amino acid metabolism. Folate is in enriched and fortified grains, green leafy vegetables, and legumes. The RDA of folate for adults is 400 mcg/day of DFEs. The recommendation is that women of childbearing age consume an additional 400 mcg/day of folic acid from supplements or fortified foods to decrease the risk of neural tube defects.
  • Vitamin B12 (Cobalamin) – Vitamin B12, or cobalamin, is an essential water-soluble vitamin that acts as coenzymes for the crucial methyl transfer reaction in converting homocysteine to methionine and the isomerization reaction that occurs in the conversion of L-methylmalonyl-CoA to succinyl-CoA. Vitamin B12 is only present in animal products because it is a product of bacteria synthesis. Many foods are also fortified with synthetic vitamin B12. The RDA of vitamin B12 for adults is 2.4 mcg/day. It is recommended for older adults to meet their RDA with fortified foods or supplements because many are unable to absorb naturally occurring vitamin B12.
  • Vitamin C (Ascorbic Acid) – Vitamin C, or ascorbic acid, is an essential water-soluble vitamin that acts as a reducing agent in enzymatic reactions and nonenzymatically as a soluble antioxidant. Vitamin C is found primarily in fruits and vegetables, except for animal organs like the liver and kidneys. The RDA of vitamin C for adult women and men is 75 mg/day and 90 mg/day, respectively. Smokers require an additional 35 mg/day of vitamin C.
  • Vitamin A (Retinol) – Vitamin A, or retinol, is an essential fat-soluble vitamin that plays numerous roles in vision, cellular differentiation, gene expression, growth, the immune system, bone development, and reproduction. Vitamin A is found primarily in animal products. Fruits and vegetables are a source of provitamin A carotenoids that can be converted to retinol in the body at a lesser amount. The RDA for vitamin A for adults is 900 mcg/day for males and 700 mcg/day for females.
  • Vitamin D (Cholecalciferol) –Vitamin D, or cholecalciferol, is an essential fat-soluble vitamin that plays an essential role in calcium metabolism, cell growth and development, and bone health. Vitamin D can be found in fish oils and in small amounts in plants in its less biologically active form. Interestingly, vitamin D synthesis occurs in the skin with exposure to UV light making dietary sources unnecessary in certain cases. The RDA for vitamin D for adults is 10 to 15 mcg/day.
  • Vitamin E (Tocopherol) – Vitamin E, or tocopherol, is a fat-soluble vitamin that is an antioxidant and may play roles in cell signaling, platelet aggregation, and vasodilation. Vitamin E, in the form of α-tocopherol, is found in certain vegetable oils, including sunflower, safflower, canola, and olive oil, whole grains, nuts, and green leafy vegetables. The RDA for vitamin E for adults is 15 mg/day.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K is an essential fat-soluble vitamin that is the coenzyme in the carboxylation of glutamic acid to form γ-carboxyglutamic acid reaction, which is essential to the proteins involved in blood coagulation. Vitamin K is present in green leafy vegetables, canola oil, and soybean oil. The RDA of vitamin K for adults is 120 mcg/day for men and 90 mcg/day for women.

Mineral

  • Calcium – Calcium is an essential macromineral responsible for numerous structural components such as bones and teeth and physiological mechanisms in the body. Calcium exists in dietary sources such as dairy, cereals, legumes, and vegetables. The RDA for calcium for adults is 1,000 mg/day.
  • Magnesium – Magnesium is an essential macromineral responsible for numerous functions in the body, including signaling pathways, energy storage, and transfer, glucose metabolism, lipid metabolism, neuromuscular function, and bone development. Magnesium is present in food sources such as fruits, vegetables, whole grains, legumes, nuts, dairy, meat, and fortified foods like cereal. The adult RDA for magnesium is 400 mg/day.
  • Phosphorus – Phosphorus is an essential macromineral that is a structural component of bones and teeth, DNA, RNA, and plasma membrane of cells. It is also critical metabolically to produce and store energy. Phosphorus is pervasive throughout food sources, with the greatest contributors being milk, dairy, meat, and poultry. Phosphorus is also an additive in processed foods as a preservative. The RDA for phosphorus for adults is 700 mg/day.
  • Sodium – Sodium is an essential macromineral and electrolyte that plays critical roles in cellular membrane transport, water balance, nerve innervation, and muscle contraction as the most abundant extracellular cation. Sodium is available in dietary sources such as salt, processed foods, meat, milk, eggs, and vegetables. The AI for sodium for adults is 1,500 mg/day; however, the average sodium intake in industrialized nations is 2 or 3 fold by comparison, at 3,000 to 4,500 mg/day.
  • Potassium – Potassium is an essential macromineral and electrolyte that plays critical roles in muscle contraction, nerve innervation, blood pH balance, and water balance as the most abundant intracellular cation. Potassium is obtainable in dietary sources such as fruits and vegetables. The AI for potassium is for adults is 4,700 mg/day.
  • Chloride – Chloride is an essential macromineral and electrolyte that plays critical roles in digestion, muscular activity, water balance, and acid-base balance as the most abundant extracellular anion in the body. Dietary chloride is almost always present in dietary sources associated with sodium in the form of NaCl or table salt. Chloride is in processed foods, meat, milk, eggs, and vegetables. The AI for chloride for adults is 1,500 mg/day.
  • Iron – Iron is an essential trace mineral that has a critical role in oxygen transport and energy metabolism. Dietary iron is from sources such as meat, fortified grains, and green leafy vegetables. Animal foods contain a more bioavailable form of iron called heme iron, while plant foods and fortified grains contain a less bioavailable form called non-heme iron. The RDA for iron for adults is 8 to 18 mg/day.
  • Zinc – Zinc is an essential trace mineral that functions structurally in proteins and catalytically as a component of over 300 different enzymes. Zinc appears in a variety of foods, especially shellfish and red meat. The RDA for zinc for adults is 10 mg/day.
  • Copper – Copper is an essential trace mineral that acts as a component of numerous proteins, including many important enzymes. Copper is in a variety of food sources but the highest concentrations in organ meats, nuts, seeds, chocolate, and shellfish. The RDA for copper for adults is 1 mg/day.
  • Iodine – Iodine is an essential trace mineral necessary for thyroid hormone synthesis. Iodine is present in meats and plant foods based on the soil content of the food production region. Otherwise, iodized salt is the main food source of iodine in regions with low soil iodine content. The adult RDA for iodine is 150 mcg/day.
  • Selenium – Selenium is an essential trace mineral that is an essential component of selenoproteins that play biological roles in antioxidant defense and anabolic processes in the human body. Selenium occurs in grains and vegetables, but the amounts vary based on the selenium content in the soil that the grains and vegetables were grown in. Brazil nuts are known for having high concentrations of selenium. The RDA for selenium for adults is 55 mcg/day.

Cellular

Carbohydrates

Carbohydrate digestion occurs in the mouth and small intestine with salivary amylase, pancreatic amylase, and brush border enzymes. Human carbohydrate digesting enzymes catalyze hydrolysis reactions that break the bonds between monomers. However, given fibers have beta bonds, they are indigestible by human enzymes, so some end up getting digested by bacterial enzymes in the large intestine, and the remainder is excreted in the feces. In the mouth, salivary amylase begins to break down the polysaccharide starch into the disaccharide maltose, which both contain monomers of glucose. Carbohydrate digestion bypasses the stomach and continues in the small intestine via pancreatic amylase and brush border enzymes on the microvilli. Pancreatic amylase continues to break down starches into maltose. The brush border enzymes include maltase, sucrase, and lactase. Maltase hydrolyzes maltose into two glucose monomers. Sucrase hydrolyzes sucrose into glucose and fructose. Lactase hydrolyzes lactose into glucose and galactose.

Monosaccharides pass through intestinal epithelial cells via facilitated diffusion and active transport to enter the bloodstream. Fructose is absorbed via facilitated diffusion by GLUT5 and released via facilitated diffusion by GLUT2. Glucose and galactose are absorbed along with sodium via active transport by the symporter sodium-glucose transporter 1 and are released via facilitated diffusion by GLUT2. The monomers enter the portal vein and travel to the liver. When fructose and galactose enter the liver, they must first be converted to glucose to be metabolized for energy. These can be converted into intermediates of the glycolysis pathway, glucose-6-phosphate or fructose-6-phosphate, to directly enter the glycolysis pathway or the substrate of glycogenesis, glucose-1-phosphate, to be stored as glycogen.

Glucose metabolism requires the following B vitamins to act as coenzymes: thiamine (B1), riboflavin (B2), and niacin (B3). Glucose metabolism begins in the cytoplasm of cells with the anaerobic process of glycolysis when one 6-carbon glucose molecule is partially oxidized into two 3-carbon pyruvate molecules. During the process, there is a net yield of two ATP and two NADH, where they will carry the electrons to the electron transport chain, eventually producing ATP. NADH is derived from niacin. ATP is the main source of cellular energy due to its high energy bonds between phosphate groups, which are released when broken via hydrolysis.

In the absence of oxygen, which can happen during strenuous exercise or in cells without mitochondria, lactate dehydrogenase catalyzes the conversion of pyruvate to lactate, which can then go back to the liver to be converted back to pyruvate and undergo gluconeogenesis to create glucose. Then, the glucose can go back to the muscle cells and go through glycolysis, again releasing two ATP molecules. This is called the Cori cycle and shows how lactate, the waste product of skeletal muscles, can be converted to glucose in hepatocytes and then be used for energy back in the skeletal muscles.

In the presence of oxygen, pyruvate will travel to the mitochondrial matrix, where pyruvate dehydrogenase will catalyze the oxidation and decarboxylation of two 3-carbon molecules of pyruvate from glycolysis into two 2-carbon molecules of acetyl-CoA. Pyruvate dehydrogenase uses thiamine pyrophosphate, or TPP, as a coenzyme. In addition, two carbon dioxide molecules and two NADH molecules are produced, and the NADH molecules will carry electrons to the electron transport chain to ultimately produce ATP. Pyruvate decarboxylation is the link between glycolysis and the citric acid cycle.

The citric acid cycle, also known as the TCA cycle and the Krebs cycle, occurs in the mitochondrial matrix where the 2-carbon acetyl-CoA will join 4-carbon oxalate to produce 6-carbon citrate, which gets degraded to produce the energetic molecules GTP, NADH, and FADH2. The cycle will continue so long as there is an input of acetyl-CoA because citrate eventually gets converted back to oxalate. Two pyruvates from glycolysis will release 2 GTP, 6 NADH, and 2 FADH molecules. FADH is derived from riboflavin. NADH and FADH2 will travel to the electron transport chain, where ATP will be synthesized via oxidative phosphorylation.

Oxidative phosphorylation begins at the electron transport chain along the inner membrane of the mitochondrion. Four protein complexes I-IV are embedded along the membrane and function to pump protons from the mitochondrial matrix to the intermembrane space to create an electrochemical gradient through a chain of redox reactions. Protein complex I receive electrons from NADH to pump hydrogen across the inner membrane. FADH2 drops electrons off at protein complex II, and protons get pumped across at protein complex III. One molecule of NADH generates three ATP molecules, while one molecule of FADH2 only generates two molecules of ATP.  When enough protons fill up the intermembrane space, an electrochemical gradient occurs. At protein complex IV, oxygen acts as the final electron acceptor, forming water. Through chemiosmosis, protons will flow from the intermembrane space through the hydrophilic tunnel of ATP synthase back to the matrix. The proton motive force generates energy that allows ATP synthase to condense ADP + Pi into high-energy ATP. Overall, this process generates 34 ATP molecules per molecule of glucose and is by far the most efficient way to produce energy.

Proteins

Protein digestion begins in the stomach, where they are broken down by the protease enzyme pepsin. First, gastric parietal cells will release hydrochloric acid, which will denature proteins and convert inactive pepsinogen to active pepsin. Pepsin digests proteins by hydrolyzing peptide bonds between amino acids to form large polypeptides or oligopeptides. Protein digestion continues in the small intestine. In response to the acidic chyme from the stomach, the hormones cholecystokinin and secretin are synthesized in the duodenum. These hormones trigger pancreatic cells to secrete bicarbonate and proenzymes into the intestine. The proenzymes trypsinogen, procarboxypeptidase, and chymotrypsinogen are converted into their active enzyme forms trypsin, carboxypeptidase, and chymotrypsin in a cascade of enzymatic reactions. Trypsin, carboxypeptidase, and chymotrypsin digest polypeptides into tripeptides, dipeptides, and free amino acids that can be absorbed in the small intestine.

Peptide and amino acid absorption occur across epithelial cells in the small intestine via transporters. Some amino acids can travel across the epithelium paracellularly, while others require amino acid transporters that vary based on the specific amino acid and mechanism in which they transport. Tripeptides and dipeptides are transported into the epithelial cell via PEPT1 coupled with the electrochemical gradient produced by the Na+/H+ exchanger on the brush border membrane. Intracellular peptides finish breaking down tripeptides and dipeptides into free amino acids. Free amino acids will exit the basolateral membrane of the epithelial cell and enter the bloodstream at the portal vein to the liver.

Amino acids can be metabolized via transamination for amino acid interconversion or deamination for the oxidation of the carbon skeleton for energy or excretion. For amino acid interconversion, pyridoxine (B6), cobalamin (B12), and folate (B9) are required. For amino acid oxidation, pyridoxine (B6), cobalamin (B12), and biotin (B7) are required. Amino acids can undergo transamination to enter the TCA cycle in glucose metabolism. Certain amino acids like alanine can be transaminated by an aminotransferase enzyme with the coenzyme PLP, which is derived from pyridoxine, to form pyruvate. Other amino acids can be transaminated by an aminotransferase enzyme with PLP to form α-ketoglutarate, an intermediate in the TCA cycle. Some amino acids can be transaminated by an aminotransferase enzyme with PLP to form oxaloacetate, which is an intermediate in the TCA cycle. Other amino acids can be oxidized with enzymes that require biotin and vitamin B12 as coenzymes or from succinyl-CoA, which is an intermediate in the TCA cycle. When the carbon skeletons of amino acids become degraded for energy, they are deaminated, and the nitrogen group is excreted in the form of urea.

Lipids

Limited digestion of lipids occurs in the mouth and stomach with the enzymes lingual lipase and gastric lipase, respectively. However, most ingested lipids arrive at the duodenum of the small intestine undigested. The presence of lipids in the duodenum stimulates the release of enzymes from the pancreas and bile from the gallbladder. Bile emulsifies that lipids preparing them for digestion by pancreatic lipase. Pancreatic lipase hydrolyzes triglycerides to monoglycerides and free fatty acids. Lipids are absorbed via simple diffusion. Short-chain fatty acids and glycerol move directly into the portal circulation and bind to albumin. Long-chain fatty acids, mono/diglycerides, cholesterol, and phospholipids combine with bile to form micelles allowing them to be soluble in the hydrophilic environment and then leave the micelle and enter the intestinal mucosa cell. In the intestinal cell, long-chain fatty acids are re-esterified to form triglycerides. Triglycerides combine with cholesterol, phospholipids, and other proteins to form chylomicrons. The chylomicrons will leave the intestinal cell and enter the lymph system, eventually entering the bloodstream through the thoracic duct.

Lipoproteins carry lipids throughout the bloodstream, and the enzyme lipoprotein lipase frees up fatty acids to be taken up by cells. In the bloodstream, the chylomicrons can deliver the dietary fatty acids to body cells, where they will form triglycerides and the remaining lipids to the liver to travel to other cells or be excreted. In the liver, triglycerides, cholesterol, phospholipids, and proteins will combine to form VLDL, which will leave the liver to deliver lipids, mainly in the form of triglycerides, to cells in the bloodstream. As VLDL delivers triglycerides to cells, it begins to shrink and become LDL. LDL continues to carry lipids to cells, but the lipids are mainly in the form of cholesterol. LDL binds to LDL receptors of cells for cholesterol to be taken up. The remaining lipids will leave cells in the form of HDL, where they will carry lipids back to the liver for either reuse or excretion. In the cells, lipids can be metabolized for energy by entering at different points of the glucose metabolism pathway. Triglycerides are broken down into glycerol and free fatty acids. Glycerol can be converted to pyruvate and catabolized for energy. Free fatty acids can be oxidized to acetyl-CoA to enter the citric acid cycle.

  • Vitamin B1 (Thiamin) – Thiamin absorption occurs mainly in the jejunum of the small intestine. Higher concentrations are absorbed via passive diffusion, while lower concentrations are absorbed via an active, carrier-mediated system that involves phosphorylation. In the blood, thiamin is transported in the erythrocytes and plasma. A small percentage of thiamin is absorbed, while the remainder is excreted in the urine.
  • Vitamin B2 (Riboflavin) – Thiamin is mainly consumed as FMN and FAD bound to a food protein. In the stomach, the acidic environment releases the coenzymes FMN and FAD from the protein. Most absorption of riboflavin occurs in the small intestine via an active or facilitated transport system. FMN and FAD must first be hydrolyzed to riboflavin by nonspecific pyrophosphatases to be absorbed. Riboflavin is transported in the plasma mainly bound to albumin and is excreted in the urine.
  • Vitamin B3 (Niacin) – At low concentrations, niacin is absorbed in the small intestine via sodium-ion-dependent facilitated diffusion. At high concentrations, niacin is absorbed in the small intestine via passive diffusion. Niacin can be transported freely in the blood in the forms of nicotinic acid or nicotinamide. Cells and tissues can take up niacin via passive diffusion or with the use of transporters. Niacin is excreted in urine as 1-methyl nicotinamide or NAM.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid is absorbed via active transport at low concentrations and passive transport at high concentrations in the small intestine. Pantothenate kinase catalyzes the synthesis of CoA from pantothenate. CoA plays an important role in the citric acid cycle in the forms of acetyl-CoA and succinyl-CoA. CoA can be hydrolyzed to pantothenate for excretion. Pantothenic acid is excreted in the urine.
  • Vitamin B6 (Pyridoxine)  – The main dietary form of vitamin B6 is pyridoxal phosphate or PLP. For PLP to be absorbed in the small intestine, it must first undergo phosphatase-mediated hydrolysis to enter the small intestine in its nonphosphorylated form. Pyridoxal, or PL, crosses the enterocyte via passive diffusion to enter the bloodstream to the liver. In the liver, PL is converted back to PLP by the enzyme PL kinase. PLP is the main circulating form of vitamin B6 and is transported in the blood bound to albumin. The majority of PLP in the body is found in the muscle. Vitamin B6 is excreted in the urine in the form of 4-pyridoxic acid.
  • Vitamin B7 (Biotin) – Biotin can be ingested as free biotin or protein-bound biotin. In the small intestine, an enzyme called biotinidase releases biotin from its covalent bond to the protein allowing it to be absorbed. Biotin is absorbed in the small intestine through a sodium-dependent transporter. Biotin is transported through the bloodstream to the liver, mostly unbound as free biotin. Biotin and biotin metabolites are excreted in the urine.
  • Vitamin B9 (Folate)  – Food folates are polyglutamate derivatives and must be hydrolyzed to the monoglutamate forms before absorption. The monoglutamate form of folate is absorbed in the small intestine via active transport. Pharmacological doses of folic acid from supplements or fortified foods are absorbed via passive transport. Folate is transported in the bloodstream to the liver in the form of 5-methyl-tetrahydrofolate. Folate is mostly bound to albumin in the bloodstream. Most ingested folate is used or stored. Any dietary folate not absorbed is excreted in feces.
  • Vitamin B12 (Cobalamin)  – Small amounts of vitamin B12 are absorbed through a coordinated process of the GI tract, given naturally occurring B12 is bound to a protein that must be released for absorption. First, in the stomach, the presence of acid and pepsin causes the dissociation of food-bound vitamin B12 from its proteins. Then R-proteins or haptocorrins, secreted by the salivary glands, bind to vitamin B12 to protect it from stomach acid. In the small intestine, pancreatic proteases degrade R-proteins to allow B-12 to bind to intrinsic factor, which is secreted by gastric parietal cells. Intrinsic factor attaches B12 to specific ileal mucosa receptors allowing the complex to be internalized by endocytosis into the enterocyte and released into the bloodstream where it is bound to transcobalamin I, II, or III. 50% of transcobalamin II bound B12 is taken up by the liver, where it is stored while the remainder is transported to other tissues. B12 is excreted in bile, but most of it ends up reabsorbed.
  • Vitamin C (Ascorbic Acid) – The absorption, tissue distribution, and excretion of vitamin C are tightly regulated by tissue-specific active transporters SVCT-1 and SCVT-2. Ascorbic acid is absorbed into the enterocyte by SVCT-1 and enters the bloodstream via SVCT-2. Other tissues take up ascorbic acid via SVCT-1 and/or SCVT-2. Vitamin C is excreted in the urine at intakes greater than 400 mg/day. Vitamin C is most concentrated in the brain, eyes, and adrenal gland.
  • Vitamin A (Retinol) – Vitamin A is ingested both in the form of retinol and provitamin A carotenoids. In the small intestine, retinol and provitamin A carotenoids enter the mucosal cell after combining with bile to form a micelle. Retinol binds to cellular retinol-binding protein (CRBP) II within the intestinal mucosal cells to form a retinol-CRBP II complex. Then, lecithin retinol aminotransferase esterifies CRBP II retinol with a fatty acid to form CRBP-retinyl palmitate. The retinol esters will be incorporated with other lipids and apoproteins to form a chylomicron. The chylomicron will leave the intestinal cell and enter the lymph system and eventually enter the blood. β-carotene, a provitamin A carotenoid, is converted to retinoic acid inside the intestinal cells and is able to directly enter the bloodstream where it attaches to albumin to be transported to the liver.
  • Vitamin D (Cholecalciferol) – Vitamin D is obtained mainly through UV-B-induced production in the skin. A minor amount of vitamin D is obtained through dietary intake. In the skin, vitamin D3, or cholecalciferol, is synthesized when 7-dehydrocholesterol is exposed to UV-B light from the sun. Vitamin D3 is transferred to the liver to be further metabolized. Through dietary intake, vitamin D3 is absorbed in the small intestine via incorporation into a micelle to enter the intestinal cells and incorporate into chylomicrons to leave the intestinal cells to enter the lymph system and eventually enter circulation the thoracic duct. In the liver, vitamin D3 enters a hepatocyte and is hydroxylated into 25-OH vitamin D3, which is catalyzed by the enzyme 25-hydroxylase. Then, 25-OH vitamin D3 bind to vitamin D-binding protein, or DBP, to leave the hepatocytes and be transported to the kidney for an additional hydroxylation reaction. In the kidney, 25-OH vitamin D3 is hydroxylated to 1,25-(OH)2 vitamin D3, which is catalyzed by the enzyme 1-hydroxylase. 1,25-(OH)2 vitamin D3 is also known as calcitriol, which is considered the active form of vitamin D. 1,25-(OH)2 vitamin D3 bound to DBP is released to the bone, immune cells, and liver cells.
  • Vitamin E (Tocopherol) – Through dietary intake, vitamin E is absorbed in the small intestine via incorporation into a micelle to enter the intestinal cells and incorporate into a chylomicron to leave the intestinal cells and enter the lymph system and eventually enter circulation the thoracic duct. Vitamin E is transported in remnant chylomicrons to the liver, where it is taken up by a hepatocyte. In the hepatocyte, α-tocopherol transfer protein incorporates α-tocopherols into very low-density lipoproteins, or VLDLs, to transport to peripheral tissues. In circulation, lipoprotein lipase (LPL) catalyzes the conversion of VLDL to LDL to HDL. The cellular uptake of α-tocopherol takes place with the uptake of lipoproteins via receptor-mediated endocytosis. Most α-tocopherol is stored in adipose tissue. The remaining tocopherols and tocotrienols are excreted with bile in feces.
  • Vitamin K (Phylloquinone; Menaquinone) – Through dietary intake, vitamin K1 and K2 are absorbed in the small intestine via incorporation into a micelle to enter the intestinal cells and incorporation into a chylomicron to leave the intestinal cells and enter the lymph system and eventually enter circulation at the thoracic duct. Vitamin K1 and K2 are transported in remnant chylomicrons to the liver where it is taken up by a hepatocyte. In the hepatocyte, vitamin K1 and K2 are incorporated into very low-density lipoproteins, or VLDLs, to transport to peripheral tissues. In circulation, lipoprotein lipase (LPL) catalyzes the conversion of VLDL to LDL to HDL. The cellular uptake of vitamin K1 and K2 takes place with the uptake of lipoproteins via receptor-mediated endocytosis. Vitamin K is stored predominantly in the liver in the form of menaquinone and is excreted in the urine and feces.
  • Calcium – The intestine, kidney, bone, and parathyroid gland work together to tightly regulate calcium balance in the body. The majority of calcium is absorbed in the small intestine via paracellular diffusion. The remainder of calcium is absorbed transcellular through the calcium channel TRPV6 when luminal calcium levels are low. Calcium is transported in the bloodstream in three forms: 48% ionized as free Ca2+, 46% bound to the protein albumin, and 7% complexed with citrate, phosphate, or sulfate. In low blood calcium concentration conditions, the parathyroid gland is stimulated to release parathyroid hormone (PTH). PTH then stimulates the kidneys to increase calcium reabsorption in the proximal convoluted tubule. PTH also stimulates the kidneys to convert 25-OH D3 into 1,25(OH)2 D3, or calcitriol. The increased calcitriol and PTH in the blood travel to the bone and stimulate the resorption of calcium and phosphorus from the bone. Calcitriol also stimulates the small intestine to increase calcium absorption. As a result, blood calcium is increased. In high blood calcium conditions, the thyroid gland releases the hormone calcitonin, preventing calcium mobilization from the bone, thus reducing blood calcium levels. 99% of the calcium in the body is found in the bones and teeth, while the remainder is found in soft tissues and plasma both intracellularly and extracellularly. Most calcium is reabsorbed in the kidney, but the remainder is excreted in urine and feces.
  • Magnesium – Magnesium is absorbed in the small intestine through paracellular diffusion and transcellular active transport via TRPM6 and TRMP7. At normal magnesium intakes, 30% of intestinal magnesium absorption occurs via transcellular transport. When magnesium intakes are lower, more magnesium is absorbed via transcellular transport. When magnesium intakes are higher, more magnesium is absorbed through paracellular diffusion. Magnesium is transported in the blood as free Mg2+(60%), protein-bound (30%), and complexed to citrate, phosphate, or sulfate (10%). The kidneys control magnesium homeostasis. About 70% of serum magnesium is available for glomerular filtration, and 96% of the filtered magnesium is reabsorbed in the kidneys through several mechanisms in the proximal tubule, ascending limb, and distal tubule. The remaining magnesium is excreted in the urine. 99% of magnesium in the body is stored intracellularly in bone, muscle, and soft tissues, while 1% of magnesium in the body is found in extracellular fluid.
  • Phosphorus –  The phosphorus is absorbed in the small intestine into the enterocyte via two processes: active transport by the apical Na+ phosphate transporter NaPi-IIb and paracellular diffusion. Phosphorous leaves the enterocyte to enter the bloodstream via facilitated diffusion. The kidney plays a role in phosphorus homeostasis through the reabsorption of inorganic phosphate from the glomerular filtrate in the proximal convoluted tubule. Approximately 75 to 85% of phosphorus is reabsorbed per day, and the remainder is excreted in the urine. Phosphorus homeostasis can also be regulated secondary to that of calcium with resorption from the bone due to high PTH and calcitriol levels. Throughout the body, phosphorus is distributed 85% in the skeleton, 0.4% in the teeth, 14% in the soft tissue, 0.3% in the blood, and 0.3% in the extravascular fluid.
  • Sodium – Sodium is absorbed in the small intestine across the brush border membrane of the enterocyte via sodium-glucose cotransporter 1 (SGLT1). SGLT 1 is an active transporter that absorbs 2 sodium ions and 1 glucose across the brush border membrane of the enterocyte. Sodium is then transported out of the enterocyte into the bloodstream across the basolateral membrane via the sodium-potassium pump, or ATPase. The sodium-potassium pump uses ATP to transport 3 sodium ions out of the enterocyte and 2 potassium ions into the enterocyte. Sodium and water balance are closely linked and maintained by the kidneys. Half of the sodium in the body is found in extracellular fluid, while around 10% is found in intracellular fluid. The remaining 40% of sodium is found in the skeleton. Small losses of sodium can occur through urine, feces, and sweat.
  • Potassium – Most of the dietary potassium is absorbed in the small intestine via passive transport. The kidney maintains potassium homeostasis. About 90% of the potassium consumed is excreted in the urine, with the remaining small amount excreted in stool and sweat. Most of the potassium content in the body is found in the intracellular space of the skeletal muscle.
  • Chloride – Chloride absorption occurs in the lumen of the small intestine via three distinct mechanisms: paracellularly through passive transport, the coupling of Na+/H+ and Cl−/HCO3− exchangers, and HCO3−-dependent Cl− absorption. Chloride is principally found in extracellular fluid. The kidneys regulate chloride concentration. Around 99% of chloride is reabsorbed in the proximal tubule of the kidneys both paracellularly and transcellular via the Cl−/HCO3− exchanger. The remainder of chloride can be excreted in urine, feces, or sweat.
  • Iron – Iron consumed from food can be present in two forms: heme and nonheme iron. 90% of dietary iron consists of nonheme iron, which is far less bioavailable than heme iron. Iron is absorbed in the small intestine in the duodenum. Given nonheme iron is often present in the form of ferric iron, it must be reduced to the ferrous form prior to enterocyte uptake with the ferric reductase enzyme DCYTB. The apical surface of the enterocyte contains divalent metal transporter 1 (DMT1), which transports ferrous iron into the enterocyte. On the basolateral membrane of the enterocyte, ferroportin releases ferrous iron to hephaestin, which oxidizes ferrous iron to ferric iron so it can bind to the transporting protein transferrin in portal circulation. Ferroportin is the main regulatory point of entry for iron in the body. Iron is stored in the liver bound to ferritin, where it can be sequestered to bone marrow for erythropoiesis or red blood cell formation. Macrophages in the reticuloendothelial system of the liver, spleen, and bone marrow can ingest old red blood cells to recycle iron to be stored in the liver. There is no specific excretory system for iron. Iron loss can only occur secondary to the exfoliation of epithelial cells in the skin and gastrointestinal tract in addition to red blood cell loss from the gastrointestinal tract.
  • Zinc – Zinc is absorbed in the small intestine via carrier-mediated transport, with ZIP4 taking zinc up into the intestinal cell and ZNT1 releasing it into the bloodstream. Zinc is bound to albumin in circulation. Zinc transporters are pervasive throughout tissues in the body and play a role in maintaining zinc homeostasis. Zinc is excreted in feces.
  • Copper – Copper absorption mainly occurs in the small intestine. Copper is taken up by enterocytes with copper transporter 1 (CTR1), which is a copper importer located at the apical membrane of intestinal cells and most tissues. Copper is exported from the enterocytes into the blood by the exporter ATP7A. In portal circulation, most of the copper is bound to the transporter protein ceruloplasmin. Copper is taken up by the liver when copper-bound ceruloplasmin binds to ceruloplasmin receptors. In the hepatocytes, protein metallochaperones serve to assign and transport copper to specific pathways throughout the body. Copper is exported from the hepatocyte via the exporter ATP7B. Excess copper is secreted in the bile, which gets excreted in the feces.
  • Iodine – Iodine can be ingested in many chemical forms. Iodide is rapidly and almost completely absorbed in the stomach and small intestine. Iodate, which is used in iodized salt, is reduced in the gut and then absorbed as iodide. In circulation, iodine is taken up mainly by the thyroid gland and kidney. Iodine uptake by the thyroid depends on iodine intake, whereas uptake by the kidney remains fairly constant. Iodine is excreted in the urine. Most of the body’s iodine is stored in the thyroid to be used in thyroid hormone synthesis.
  • Selenium – The mechanism of selenium absorption is not well known. Selenium absorption occurs in the small intestine via mechanisms dependant upon the form of selenium. The absorption of inorganic selenate occurs through active transport with a sodium pump. The absorption of inorganic selenite occurs via passive diffusion. Organic selenomethionine and selenocysteine are absorbed via an active transport mechanism similar to that of neutral amino acids like methionine. Selenium is absorbed into the portal bloodstream from the enterocyte and is transported to the liver in multiple forms. Selenite is taken up by erythrocytes and reduced by glutathione reductase to selenide, which is transported in the plasma bound to albumin. Selenium can also be transported in the form of selenoprotein P. Sometimes, selenium may bind to LDL and VLDL. Selenium is stored in tissues in the form of selenomethionine with variable densities in the liver, muscle, kidney, plasma, and other organs. Selenium excretion via urine in the form of methylselenol.

Molecular

Carbohydrates

Carbohydrates are organic molecules made up of carbon, hydrogen, and oxygen. Carbohydrates are classified based on their chemistry: individual monomer characteristics, degree of polymerization, and type of linkages (α or β). Given this classification, carbohydrates subdivide into three main groups: sugars (degree of polymerization = 1 to 2), oligosaccharides (degree of polymerization = 3 to 10), and polysaccharides (degree of polymerization more than 10). Sugars include monosaccharides and disaccharides. The most common monosaccharides are glucose, fructose, and galactose. The most common disaccharides are sucrose, lactose, and maltose. Examples of oligosaccharides include maltodextrins, raffinose, and polydextrose. Polysaccharides include starches and non-starch polysaccharides. Starches include digestible amylose due to its alpha-linked monosaccharides. Non-starch polysaccharides include non-digestible cellulose due to their β-linked monosaccharides.

Proteins

Proteins are polymers of amino acids. Amino acids are organic molecules composed of carbon, hydrogen, oxygen, and nitrogen. The general structure of an amino acid consists of a central carbon surrounded by hydrogen, an amino group, a carboxylic acid group, and a side chain “R.” Each amino acid has a unique side chain. Nine essential amino acids must come from dietary sources: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The body can make eleven non-essential amino acids from precursors: alanine, arginine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, and tyrosine. There are four structure levels in a protein: primary, secondary, tertiary, and quaternary. The primary structure of a protein is a chain of amino acids connected by peptide bonds; this determines the subsequent structures and biological functions of the protein. The secondary structure of a protein consists of hydrogen bonding within amino acid chains that create either an α-helix or β-sheet conformation. The tertiary structure of a protein derives from attractions between α-helices and β-sheets of a polypeptide resulting in a three-dimensional arrangement of a protein. The quaternary structure of an amino acid consists of a spatial arrangement of multiple polypeptides in a protein.

Lipids

Lipids are organic molecules that share the common property of being hydrophobic. Dietary lipids are often in the forms of triglycerides, phospholipids, cholesterol, and fatty acids. Fatty acids are classified as saturated or containing no carbon-carbon double bonds, or unsaturated, or containing at least one carbon-carbon double bond. Saturated fatty acids have higher melting points than unsaturated fatty acids, making them solid at room temperature, unlike liquid unsaturated fatty acids. Triglycerides are composed of one 3-carbon glycerol backbone and three fatty acids. Phospholipids contain a phosphate head connected to a glycerol molecule, connected to two fatty acids. Cholesterol is a sterol that is composed of a hydrocarbon ring structure.

  • Vitamin B1 (Thiamin) – Thiamin consists of pyrimidine and thiazole rings that are linked by a methylene bridge. Thiamin exists in a variety of phosphorylated forms. Its main form is thiamin pyrophosphate or TPP.
  • Vitamin B2 (Riboflavin) – The basic chemical structure of riboflavin consists of a flavin group formed by the tricyclic heterocyclic isoalloxazine and a ribitol sugar group. The main coenzyme forms of riboflavin are flavin mononucleotide or FMN and flavin adenine dinucleotide, or FAD.
  • Vitamin B3 (Niacin) – Niacin refers to nicotinamide, nicotinic acid, and other derivatives. The basic chemical structure of nicotinic acid consists of a pyridine ring with a substituted carboxylic acid group. The chemical structure of nicotinamide consists of a pyridine ring with a substituted amide group. The main coenzyme forms of niacin are nicotinamide adenine dinucleotide or NAD and nicotinamide adenine dinucleotide phosphate or NADP.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid is a water-soluble vitamin synthesized from the condensation reaction of pantoic acid and β-alanine in only plants and bacteria. Pantothenic acid serves to transfer and carry acyl groups.
  • Vitamin B6 (Pyridoxine)  – Vitamin B6 is a generic term for six related compounds: pyridoxal (PL), pyridoxamine (PM, pyridoxine (PN), and their respective 5’-phosphatase forms (PLP, PMP, and PNP). The major forms of vitamin B6 in animal tissues are PLP and PMP.
  • Vitamin B7 (Biotin) – Biotin’s chemical structure consists of a heterobicyclic ring of radio and thiophene with a valeric acid side chain.
  • Vitamin B9 (Folate) – Folate is the generic term for the different forms of vitamin B9 that function in single-carbon transfers. The most oxidized and stable form of folate called folic acid is in vitamin supplements. It consists of a p-aminobenzoic acid molecule bound to a pteridine ring on one side and a glutamic acid molecule on the other side. Naturally occurring folates found in food, called food folate, are pteroylpolyglutamates, which contain between one and six additional glutamate molecules connected by a peptide linkage to glutamate’s γ-carboxyl.
  • Vitamin B12 (Cobalamin) – Cobalamin, or vitamin B12, is a generic term for a group of cobalt-containing compounds with a corrin ring attached to 5,6-dimethylbenzimidazole, a sugar ribose, and a phosphate. The two cobalamins that are active in human metabolism as coenzymes are methylcobalamin and 5-deoxyadenosylcobalamin.
  • Vitamin C (Ascorbic Acid) – Vitamin C, or ascorbic acid, chemically is a simple carbohydrate with an ene-diol structure that makes it an essential water-soluble electron donor. The main form of vitamin C found in foods is its reduced form – ascorbic acid. Ascorbate is the main circulating form of vitamin C in the body.
  • Vitamin A (Retinol) – Vitamin A is a generic descriptor for compounds that exhibit the biological activity of retinol and provitamin A carotenoids. Retinol is an unsaturated 20-carbon cyclic alcohol. Provitamin A carotenoids exhibit a 40-carbon basal structure with cyclic end groups and a conjugated system of double bonds.
  • Vitamin D (Cholecalciferol) – Vitamin D3, or cholecalciferol, had a chemical structure that contains three steroid rings and an eight-carbon side chain. The structure derives from cholesterol.
  • Vitamin E (Tocopherol) – The term vitamin E encompasses eight lipophilic compounds that include four tocopherols and four tocotrienols, each of which has a designation as α-, β-, γ-, and δ-. Each of these compounds contains a chromanol ring and a lipophilic tail. Tocotrienols differ from tocopherols with their unsaturated side chains. α-tocopherol is the only form of vitamin E that is known to reverse deficiency symptoms.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K occurs naturally in two main forms: K1, or phylloquinone, and K2, or menaquinone, which has many different forms. Also, vitamin K occurs in the synthetic form of vitamin K3, or menadione, which contains only the 2-methyl-1, a 4-naphthoquinone nucleus common to all forms of vitamin K. The natural forms differ by the number of isoprenoid units in their isoprenoid side chains.
  • Calcium – Calcium is an alkaline earth metal cation found in the form of Ca2+. Calcium is a critical divalent cation in intracellular and extracellular fluid.
  • Magnesium – Magnesium is an alkaline earth metal cation found in the form of Mg2+. Magnesium is the second most abundant intracellular cation in the body.
  • Phosphorus – Phosphorous is a multivalent nonmetal that occurs in both inorganic and organic forms throughout the body. The organic forms of phosphorus include phospholipids and various phosphate esters. The inorganic forms of phosphorus include phosphate ions, protein-bound phosphate, and calcium, sodium, or magnesium-bound phosphate. Most phosphorus exists in the form of an inorganic free phosphate ion (PO42- or PO43-).
  • Sodium – Sodium is an alkali metal cation found in the form of Na+. Sodium is the major extracellular cation in the body.
  • Potassium – Potassium is an alkali metal cation found in the form of K+. Potassium is the major intracellular cation in the body.
  • Chloride – Chloride is a nonmetal anion found in the form of Cl-. Chloride is the body’s principal anion making up 70% of the body’s total anion content and serves as the most important extracellular anion in the body.
  • Iron – Iron is a transition metal element. Iron exists in two main oxidation states: Fe2+ and Fe3+. The more bioavailable form of iron is its reduced form ferrous iron, or Fe2+, due to its solubility. The less bioavailable form of iron is its oxidized form ferric iron, or Fe3+, due to its lack of solubility. Heme iron is contained in the protoporphyrin ring of hemoglobin, myoglobin, and cytochromes and is highly bioavailable. Nonheme iron can be found in molecules like iron-sulfur enzymes and ferritin and is less bioavailable.
  • Zinc – Zinc is a metal that exists in the form of Zn2+. With the 2+ charge, zinc is a strong electron acceptor in biological systems.
  • Copper – Copper is a transition metal that exists in the forms of Cu+ and Cu2+. Cu+ is the cuprous reduced form of copper. Cu2+ is the cupric oxidized form of copper. Copper is absorbed into cells in its reduced form but is ingested and travels through the bloodstream in its oxidized form.
  • Iodine – Iodine is a nonmetal element identified by its distinct violet vapor. Iodine is consumed and absorbed in its reduced form of iodide (I-). Iodine is also consumable in its oxidized form of iodate (IO3-), as well as when it is organically bound to thyroxine (T4) and triiodothyronine (T3).
  • Selenium – Selenium is present in nature in both organic and inorganic forms. The main organic forms of selenium are selenomethionine and selenocysteine. The inorganic forms of selenium are selenite (SeO32-), selenide (Se2−), selenate (SeO42-), and selenium element (Se).

Function

Macronutrients – Carbohydrates, Proteins, Lipids

Macronutrients mainly function to supply energy. Carbohydrates function as the main source of cellular energy from the human diet and are particularly essential to supply energy to the glucose-dependent brain and nervous system. Fiber plays a role in lowering cholesterol by binding to bile and promoting gut health. Proteins function less favorably as a source of energy because they play crucial roles in regulating body processes and contributing majorly to cell and body structure. Proteins particularly function as hormones, enzymes, transporters, and antibodies. Lipids function as a source of stored energy, contribute to cell function and structure and protects body organs. Water acts as a solvent for chemical reactions, a medium for nutrient transport, and a thermoregulator.

  • Vitamin B1 (Thiamin) – The coenzyme form of thiamin, or TPP, is involved in the following types of metabolic reactions: decarboxylation of α-keto acids and transmetalation. These occur in carbohydrate and branched-chain amino acids metabolism.
  • Vitamin B2 (Riboflavin) – Riboflavin functions as a component of the metabolically essential coenzymes FMN and FAD. FMN and FAD can serve as intermediates in electron transfer in redox reactions. As coenzymes, FAD and FMN are often bound to enzymes that are oxidases and dehydrogenases.
  • Vitamin B3 (Niacin) – Niacin functions as a component of the metabolically essential coenzymes NAD and NADP. These coenzymes act as hydride ion acceptors or donors in biological redox reactions. They also serve as coenzymes for dehydrogenases.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid functions as a supporter of the synthesis and maintenance of coenzyme A, a cofactor and acyl group carrier for other enzymes, and an acyl protein carrier in the fatty acid synthase complex.
  • Vitamin B6 (Pyridoxine) – Vitamin B6, in the form of PLP, is a coenzyme for over 100 enzymes involved in amino acid metabolism. PLP is a coenzyme for aminotransferases, decarboxylases, racemases, and dehydratases. PLP is a coenzyme in the first step of heme biosynthesis and the transsulfuration of homocysteine to cysteine.
  • Vitamin B7 (Biotin) – Biotin functions in metabolism as a coenzyme for transferring single-carbon units in the form of carbon dioxide for the following carboxylases: pyruvate carboxylase, propionyl-CoA carboxylase, acetyl-CoA carboxylase, and β-methylcrotonyl-CoA carboxylase. These enzymes play roles in gluconeogenesis, citric acid cycle, fatty acid synthesis, and leucine degradation.
  • Vitamin B9 (Folate)  – Folate functions in nucleic and amino acid metabolism as a coenzyme in single-carbon transfers. Folate functions as a coenzyme in nucleic acid metabolism in the processes of DNA synthesis in purine and pyrimidine nucleotide biosynthesis.  Folate functions as a coenzyme in amino acid metabolism in amino acid interconversions, including the conversion of homocysteine to methionine, which serves as the major source of methionine for the formation of the major methylating agent S-adenosyl-methionine.
  • Vitamin B12 (Cobalamin)  – Cobalamin functions as a coenzyme for two enzymes in human metabolism: methionine synthase and L-methylmalonyl-CoA mutase. Vitamin B12, in the form of methylcobalamin, is required as a coenzyme to methionine synthase for the methyl transfer reaction from methyltetrahydrofolate to homocysteine resulting in the formation of methionine and tetrahydrofolate. Vitamin B12, in the form of adenosylcobalamin, is required as a coenzyme to  L-methylmalonyl-CoA mutase in the isomerization reaction that results in the conversion of L-methylmalonyl-CoA to succinyl-CoA.
  • Vitamin C (Ascorbic Acid) – Vitamin C, in the form of ascorbate, has both enzymatic and nonenzymatic functions in the body. Ascorbate functions as a coenzyme as a reducing agent in the synthesis reactions of collagen, carnitine, neurotransmitters, and tyrosine. Ascorbate functions nonenzymatically as a powerful water-soluble antioxidant with the ability to reduce free radicals and reactive oxygen species. Ascorbate notably reduces glutathione radicals produced by the electron transport chain.
  • Vitamin A (Retinol) – Vitamin A functions metabolically in vision, cellular differentiation, gene expression, growth, immune system, and reproduction. In the form of 11-cis-retinal, Vitamin A is the chromophore group of rhodopsin found in the rod cells of the retina and is essential for night vision. In the form of retinoic acid, Vitamin A is required for the differentiation of certain cells like keratinocytes to epidermal cells and squamous epithelial keratinizing cells to mucous-secreting cells. Vitamin A can regulate gene expression by acting as transcription factors when bound to RAR and RXR. Vitamin A protects against xerophthalmia by maintaining normal growth of the conjunctival membranes of the eye. Vitamin A plays roles in processes involved in innate and adaptive immunity, including cell differentiation and hematopoiesis. Vitamin A plays a vital role in spermatogenesis in reproduction.
  • Vitamin D (Cholecalciferol) – Vitamin D, in its active form 1,25-(OH)2 vitamin D3, can function as a hormone by binding to receptors on target tissues to activate a signal transduction pathway and a regulator of gene expression by binding to a nuclear receptor to affect transcription. One of the most important functions of 1,25-(OH)2 vitamin D3 is to work with parathyroid hormone to maintain blood calcium homeostasis. 1,25-(OH)2 vitamin D3 functions to increase the absorption of calcium in the small intestine and reabsorption of calcium in the kidneys in response to low blood calcium. It also works with parathyroid hormone to stimulate the resorption of calcium from the bone to increase blood calcium levels. 1,25-(OH)2 vitamin D3 can also bind to various nuclear vitamin D receptors, or VDRs, in the bones, intestines, kidneys, and skin to stimulate the transcription of genes. This process is key to osteoclast maturation.
  • Vitamin E (Tocopherol) – Vitamin E is best known to function as a chain-breaking antioxidant that neutralizes the lipid peroxyl radicals during lipid peroxidation to prevent cyclic propagation of lipid peroxidation. This process is key in protecting the polyunsaturated fatty acids within the phospholipids of plasma membranes and plasma lipoproteins.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K mainly functions in the synthesis of several blood coagulation factors. It also plays a role in bone mineralization. Vitamin K performs these functions by enabling the carboxylation of glutamic acid residues in proteins to form γ-glutamic carboxyl (Gla) residues. Gla residues enable proteins to bind with calcium and interact with other proteins, which is necessary for blood coagulation and bone mineralization.
  • Calcium – 99% of the calcium in the body is in bone and teeth as a structural component. The remaining calcium in the body is found in intracellular and extracellular spaces and plays key roles in innervation, muscle contraction, blood coagulation, hormone secretion, and intracellular adhesion.
  • Magnesium – Magnesium is an important intracellular cation for numerous functions throughout the body. Magnesium plays a key role in metabolic reactions such as energy storage, glucose metabolism, and nucleic acid and protein synthesis. Magnesium also functions in oxidative reactions, immune function, and bone development. Magnesium plays a role in stabilizing excitable membranes by maintaining electrolyte balance and homeostasis of calcium, sodium, and potassium. Magnesium acts as a calcium channel antagonist and plays a role in vasodilation.
  • Phosphorus – Phosphorus has various structural and metabolic functions throughout the body. Structurally, phosphorus functions to form the structure of bone and teeth along with calcium, the phosphate backbone of DNA and RNA, and the phospholipid bilayer of cell membranes. Metabolically, phosphorus functions to create and store energy in phosphate bonds of ATP, regulate acid/base balance in the blood as a buffer, regulate gene transcription, regulate enzyme activity, and enable signal transduction of numerous regulatory pathways.
  • Sodium – As an extracellular cation, sodium functions to regulate blood volume, blood pressure, osmotic equilibrium, and pH. Sodium and potassium ions function together to create an action potential maintained by ion pumps that allow for neurotransmission, muscle contraction, and heart function. Sodium also plays a critical role in the transport of nutrients across the plasma membrane.
  • Potassium – Potassium is critical for normal cellular function. Sodium and potassium ions function together to create an action potential maintained by Na+-K+ ATPase, allowing for neurotransmission, muscle contraction, and heart function. Potassium also works alongside sodium to maintain intracellular and extracellular osmotic pressure.
  • Chloride – As the most important extracellular anion in the body, chloride functions to maintain fluid balance, acid-base balance, electrolyte balance, electrical neutrality, and muscle function throughout the body. Chloride works with sodium to maintain fluid balance. Chloride also works with bicarbonate to maintain acid-base balance.
  • Iron – Iron’s functions are essential for oxygen transport and cell proliferation—iron functions as the core of heme proteins like myoglobin, hemoglobin, and cytochromes. Myoglobin and hemoglobin are essential for oxygen storage and transport, while cytochromes are essential for electron transport chain reactions in energy metabolism. Iron is also critical in its nonheme form in iron-sulfur enzymes like succinate dehydrogenase and NADH dehydrogenase in oxidative metabolism.
  • Zinc – Zinc functions structurally as a component of proteins and catalytically as a component of >300 enzymes in the body. Zinc’s functions are pervasive throughout the body and crucial to growth, immunity, cognitive function, and bone health.
  • Copper – Copper functions as a critical cofactor to a group of cellular transporters called cuproenzymes. Copper is essential for the proper function of human organs and metabolic processes such as hemoglobin synthesis, neurotransmitter synthesis, iron oxidation, cellular respiration, antioxidant peptide amidation, pigment formation, and connective tissue formation.
  • Iodine – The primary function of iodine is its role in the synthesis of thyroid hormones thyroxine (T4) and triiodothyronine (T3). At the apical surface of the thyrocyte, iodide is oxidized by the enzymes thyroperoxidase (TPO) and hydrogen peroxide to attach it to tyrosyl residues on thyroglobulin to produce the precursors of thyroid hormones: monoiodotyrosine (MIT) and diiodotyrosine (DIT). TPO then catalyzes the formation of a diether bridge between the phenyl groups of iodotyrosine to create thyroid hormones. The linkage of two DITs produces T4, while the linkage of MIT and DIT produces T3. T3 and T4  are almost structurally identical, but T3 has one less iodine than T4. Thyroid hormones function to regulate fetal cell growth, postnatal growth, and basal metabolic rate.
  • Selenium – Selenium functions as an essential component of selenoproteins that play major roles in dense against oxidation, thyroid hormone formation, DNA synthesis, reproduction, and fertility. The functions of most selenoproteins are unknown, but the known functions involve participation in antioxidant and anabolic processes. A family of antioxidant enzymes named glutathione peroxidases is dependent upon selenium to function to neutralize hydrogen peroxide and organic hyperoxides in both intracellular and extracellular compartments. Deiodinases are a group of three selenoenzymes responsible for converting T4 to T3 in thyroid hormone activation. Selenoprotein-P is the most abundant selenoprotein found in plasma and plays a major role in the transport and homeostasis of selenium in tissues.

Testing

Carbohydrates

Measuring the amount of glucose in plasma is one of the most important ways to screen for and manage diabetes. To clinically test and monitor blood glucose, blood is drawn from a vein, usually when the patient has fasted for at least 8 hours. The level of glucose is measured in milligrams of glucose per deciliter plasma. A healthy fasting blood glucose level is less than or equal to 99 mg/dL. Someone who has an increased risk for diabetes, or prediabetes, falls in the range of fasting blood glucose of 100 to 125 mg/dL. If a patient has a fasting blood glucose of 126 mg/dL or greater on two separate occasions, they can receive a diagnosis of diabetes.

Proteins

Nitrogen balance is the gold standard for testing the protein status of the body. Nitrogen balance can serve as a marker of adequate nutrition and physiological stress. Nitrogen balance is equal to the grams of nitrogen consumed minus the grams of nitrogen excreted. The grams of nitrogen consumed is calculated by the grams of protein consumed divided by 6.25 grams of protein per 1 gram of nitrogen. The grams of nitrogen excreted is calculated by extrapolating losses with grams of nitrogen in urinary urea plus 4 grams, which accounts for losses in feces, sweat, skin, and wounds. Under normal conditions, an individual should be at nitrogen equilibrium, or nitrogen balance equals zero. Critically ill patients often have negative nitrogen, so the goal with them is to increase the protein intake to achieve a positive nitrogen balance for healing.

Lipids

To test the amount of lipids in the body, a sample of blood is taken via venipuncture in tubes and analyzed for serum or plasma total cholesterol, triglycerides, and lipoproteins. Cholesterol levels remain fairly constant so that sampling is possible at any time. In contrast to cholesterol levels, triglyceride levels fluctuate throughout the day, so blood collection should occur after a 12-hour fasting period because, at that point, chylomicrons should have cleared from the circulation. To separate and quantify lipoproteins from the plasma sample, ultracentrifugation, precipitation, and electrophoresis are performed. High vs. low plasma lipid levels are determined based on the bell-shaped distribution of the general population. Cholesterol levels are determined based on the risk for coronary atherosclerosis. Cholesterol levels below 200 mg/dl are considered desirable, levels from 200 to 239 mg/dl are considered borderline high cholesterol, and levels of 240 mg/dl or greater are considered high cholesterol.

  • Vitamin B1 (Thiamin) – Thiamin status is measurable via urinary thiamin excretion, erythrocyte thiamin, and erythrocyte transketolase activity. Erythrocyte transketolase activity is considered the gold standard functional test of thiamin status.
  • Vitamin B2 (Riboflavin) – Riboflavin status is measured via erythrocyte glutathione reductase activity, erythrocyte flavin, and urinary flavin. Erythrocyte glutathione reductase activity is the most common method to determine riboflavin status.
  • Vitamin B3 (Niacin) – Niacin status can be measured using urinary 1-methyl nicotinamide excretion, plasma concentrations of 2-pyridone, erythrocyte pyridine nucleotides, and transfer of adenosine diphosphate ribose as a functional measurement. Urinary 1-methyl nicotinamide is the most reliable and sensitive measure of niacin status.
  • Vitamin B5 (Pantothenic Acid) – Pantothenic acid status can be measured using urinary pantothenic acid excretion and whole blood pantothenic acid concentration.
  • Vitamin B6 (Pyridoxine)  – Vitamin B6 status assessment is best with plasma PLP. A plasma PLP of <20 nmol/L indicates a vitamin B6 deficiency.
  • Vitamin B7 (Biotin) – Biotin status is measurable with urinary biotin and 3-hydroxyisovalerate excretion. Decreased urinary excretion of biotin along with increased urinary excretion of 3-hydroxyisovalerate indicates biotin deficiency.
  • Vitamin B9 (Folate)  – The primary test used to measure folate status is erythrocyte folate. Given folate is taken up by developing erythrocytes in the bone marrow, erythrocyte folate concentration is an ideal indicator of long-term folate status. Plasma homocysteine can also be useful as an indicator of folate status given in inadequate quantities of folate; not as much homocysteine can undergo conversion to methionine. Serum folate can also be tested as an indicator of dietary folate intake but is limited and should be used in conjunction with additional folate status indicators.
  • Vitamin B12 (Cobalamin)  – The primary test to measure vitamin B12 status is serum vitamin B12, reflecting both intake and stores. The lower limit of serum vitamin B12 for adults is 170 to 250 pg/mL. Serum methylmalonic acid concentration is another specific and functional indicator of vitamin B12 status because serum methylmalonic acid concentrations become elevated during vitamin B12 deficiency. Serum total homocysteine concentration is a functional but non-specific indicator of vitamin B12 status due to elevation during vitamin B12 deficiency.
  • Vitamin C (Ascorbic Acid – Vitamin C status testing is via plasma vitamin C and leukocyte vitamin C. Plasma vitamin C concentration is sensitive to a recent diet, while leukocyte vitamin C reflects tissue stores. A plasma vitamin C concentration of less than 0.2 mg/dL is considered deficient.
  • Vitamin A (Retinol) – The gold standard for testing vitamin A status is through a liver biopsy because the liver is vitamin A’s major storage organ. However, this measure is not very feasible in humans. Retinol status is testable with plasma retinol concentration, but it only indicates low status if there is a severe deficiency. Vitamin A status may also be tested with a relative dose-response test, which measures the magnitude of increased RBP following supplementation.
  • Vitamin D (Cholecalciferol) – Vitamin D status is tested by using serum 25-hydroxyvitamin D concentrations. A serum 25-hydroxyvitamin D concentration that is less than 20 ng/mL represents a vitamin D deficiency and a need for supplementation.
  • Vitamin E (Tocopherol) – Vitamin E status is difficult to test because serum concentrations of vitamin E are largely age-dependent and are influenced by blood lipids. In the general population, α-tocopherol plasma levels can range from 19.9 micromoles/L to 34.2 micromoles. More research needs to be done to adjust specific requirements to an individual’s bioavailability.
  • Vitamin K (Phylloquinone; Menaquinone) – Vitamin K status is difficult to assess due to its being lipophilic and not very abundant. However, functional tests such as prothrombin time or Gla protein measurement can be useful to assess vitamin K status indirectly.
  • Calcium – Calcium status is difficult to assess in individuals because there is no reliable indicator that can establish a relationship between calcium and a particular disease state. Total body calcium is not useful to assess calcium intake because the body regulates calcium in a very tight range and will adapt to conserve it. Bone-mass measurements may indicate long-term calcium status by assessing changes in bone density.
  • Magnesium – Magnesium status can be tested with serum magnesium. Serum magnesium is maintained at a tight range of 1.7 to 2.6 mg/dL. A serum value of under 1.7 mg indicates a magnesium deficiency. A serum value of over 2.6 mg/dL indicates magnesium toxicity.
  • Phosphorus – Serum phosphorus is the most common way to assess phosphorus status. Serum phosphorus is maintained in a relatively narrow range of 2.5 to 4.5 mg/dL. Although serum phosphorus does not reflect the full body stores, serum phosphorus is crucial for various cellular processes in the body. Serum phosphorus below or above the normal range can indicate a deficiency and toxicity, respectively.
  • Sodium – Sodium balance is tested via plasma sodium concentration. A plasma sodium concentration greater than 150 mmol/L indicates sodium toxicity or hypernatremia. A plasma sodium concentration of less than 136 mmol/L indicates sodium deficiency or hyponatremia.
  • Potassium – Potassium balance is tested via serum potassium. The body maintains normal serum potassium levels in a narrow range of 3.5 to 5.5 mmol/L. Potassium toxicity, or hyperkalemia, occurs at serum potassium concentrations greater than 5.5 mmol/L. Potassium deficiency, or hypokalemia, occurs at concentrations less than 3.5 mmol/L.
  • Chloride – Since chloride serves as an important diagnostic indicator for various diseases, it can be tested for in serum, sweat, urine, and feces. Serum and urine chloride concentrations are used in the diagnosis of acid-base and osmolar disorders and used in formulas like the anion gap, strong anion gap, strong ion difference, and chloride/sodium ratio. Sweat chloride concentration is used in the diagnosis of cystic fibrosis when it is above 60 mmol/L.
  • Iron  – Iron is tested via serum-based indicators of iron status, such as hemoglobin, plasma ferritin, and plasma transferrin saturation. Hemoglobin is routinely measured to indicate anemia but is not specific for iron. Plasma ferritin is the gold standard of iron status because it is the most specific indicator of iron stores. A plasma ferritin concentration of less than 20 ng/L indicates iron deficiency. High plasma ferritin values can indicate iron overload. Transferrin saturation indicates the ratio of iron to transferrin to reflect transport iron. Transferrin saturation is low-cost but shows a pronounced diurnal variation.
  • Zinc – Zinc status testing is via serum zinc. A concentration of zinc below the lower value of the reference range of 10 to 18 micromol/L is considered a deficiency.
  • Copper – Copper status evaluation is via serum copper or serum ceruloplasmin. A concentration of serum copper below the lower value of the reference range of 12 to 20 micromol/L is considered a deficiency.
  • Iodine – Iodine status can be assessed with four different methods: urinary iodine concentration, goiter rate, serum TSH, and serum Tg. Urinary iodine, serum Tg, and goiter rate are complementary tests given urinary iodine are sensitive to recent iodine intake in a matter of days, serum Tg shows an intermediate response in a matter of weeks or months, and goiter rate changes reflect iodine nutrition in a matter of months or years. TSH can be used to assess iodine status reflecting on the level of circulating thyroid hormone but is a relatively insensitive indicator of iodine status in adults. However, TSH is a sensitive indicator of iodine status in newborns.
  • Selenium – Selenium status is tested via serum selenium. A concentration of selenium below the lower value of the reference range of 0.75 to 1.85 micromol/L is considered a deficiency.

Clinical Significance

Carbohydrates

Diabetes refers to a group of metabolic diseases of disordered glucose metabolism. Diabetes is characterized by hyperglycemia, or high blood sugar, and premature vascular disease. Symptoms of diabetes-related hyperglycemia include polydipsia, polyuria, weight loss, polyphagia, and blurred vision. Acute and life-threatening complications of uncontrolled diabetes include hyperglycemia with diabetic ketoacidosis or nonketotic hyperosmolar syndrome. Long-term complications of uncontrolled diabetes include macrovascular and microvascular complications that lead to loss of vision, renal failure, neuropathy, and cardiovascular disease. There are three types of diabetes: type 1, type 2, and gestational. Type 1 diabetes occurs in 5 to 10% of cases and is characterized by absolute insulin deficiency and pancreatic beta-cell destruction. Insulin is a hormone produced by pancreatic beta cells that stimulate sugar uptake in the blood by cells. Insulin therapy is required to treat type 1 diabetes. Type 2 diabetes occurs in 90 to 95% of cases and is characterized by insulin resistance and impaired beta-cell function. In some individuals with type 2 diabetes, blood glucose control can be managed with lifestyle changes like diet, weight reduction, and exercise, and/or oral glucose-lowering medications. However, some individuals may need insulin therapy. Gestational diabetes occurs in 9% of pregnant women during the second or third trimester of pregnancy. Glucose tolerance usually returns to normal after delivery, but this increases the risk for type 2 diabetes later in life.

Proteins

Protein-energy malnutrition is a problem for children in developing and developed countries around the world and contributes to acute and chronic childhood illness. In cases of extreme protein-energy malnutrition, marasmus and kwashiorkor are the two main clinical syndromes seen. Marasmus is more common and is characterized by muscle wasting and depletion of subcutaneous fat stores without edema as a result of deprivation of calories and nutrients. In addition, there is poor growth, little disease resistance, slowed metabolism, and impaired brain development. This usually occurs in children under the age of 5 due to their increased caloric requirements. Kwashiorkor is characterized by normal weight with edema, poor growth, low blood albumin, little disease resistance, and apathy resulting from a diet with an adequate caloric intake but inadequate protein. This commonly occurs in older infants or toddlers who are displaced from breastfeeding due to the birth of a younger sibling and have to wean rapidly but are unable to increase protein intake enough.

Lipids

Lipids in abnormal concentrations attract clinical attention. Abnormal lipid levels can occur due to abnormalities in the synthesis, degradation, and transport of lipoprotein particles. Hyperlipidemia is defined as elevated levels of lipids or lipoproteins in the blood. Hyperlipidemia is very clinically relevant due to its association with an increased risk of atherosclerotic cardiovascular disease. Other clinical manifestations of hyperlipidemia include ischemic vascular disease, acute pancreatitis, and visible accumulations of lipid deposits. Increased plasma lipid levels can be related to genetic disorders, dietary factors, certain drugs, and as a secondary symptom of certain diseases.

Vitamin B1 (Thiamin)

Thiamin deficiency is historically known as a disease called beriberi. Currently, in developed nations, thiamin deficiency mainly occurs with chronic alcoholism and is called Wernicke-Korsakoff syndrome. Symptoms of thiamin deficiency are nonspecific and include anorexia, weight loss, apathy, short-term memory issues, confusion, irritability, muscular weakness, and enlargement of the heart.

Vitamin B2 (Riboflavin)

The symptoms of riboflavin deficiency include sore throat, angular stomatitis, glossitis, dermatitis, and weakness. It is rare but can occur with diseases such as cancer, diabetes, cardiac disease, and alcoholism.

Vitamin B3 (Niacin)

The classic clinical manifestation of severe niacin deficiency is a disease called pellagra. Pellagra is characterized by a symmetrical, pigmented rash that develops in sunlight exposed areas, GI symptoms such as vomiting, constipation, diarrhea, a bright red tongue, and neurological problems such as depression and fatigue, apathy, headache, and loss of memory. Pellagra was common in the United States and Europe in areas where corn was a dietary staple in the early twentieth century. Pellagra has disappeared from developed countries except for cases of chronic alcoholism. It persists in parts of India, China, and Africa.

Vitamin B5 (Pantothenic Acid)

Pantothenic acid deficiencies are extremely rare but have been shown in individuals fed diets devoid of pantothenic acid. Symptoms of deficiency include irritability, fatigue, apathy, sleep disturbances, GI complaints, numbness, paresthesias, muscle cramps, and hypoglycemia with increased insulin sensitivity.

Vitamin B6 (Pyridoxine) 

Vitamin B6 deficiency is rare in healthy individuals. Symptoms of vitamin B6 deficiency include seborrheic dermatitis, microcytic anemia, convulsions, and confusion. Microcytic anemia occurs due to PLP’s role as a cofactor in the first step in heme biosynthesis.

Vitamin B7 (Biotin)

Biotin deficiency is rare but can occur in specific scenarios. Biotin deficiency can occur in people who ingest raw eggs due to the protein avidin, which inhibits biotin absorption. It can also occur in people with genetic defects in the enzyme biotinidase. Symptoms of biotin deficiency include thinning of hair, loss of hair color, dermatitis, depression, lethargy, and hallucinations.

Vitamin B9 (Folate) 

Folate deficiency results in impaired synthesis of DNA and RNA, which can manifest clinically megaloblastic anemia and developmental disorders in utero. Megaloblastic or macrocytic anemia occurs when red blood cell development is halted in the early erythroblast stage due to a lack of folate, allowing DNA synthesis to continue and erythroblasts to divide and mature. Early erythroblasts are large and do not contain much hemoglobin. Inadequate maternal folate status during pregnancy can result in neural tube defects such as spina bifida and anencephaly. Neural tube defect risk reduction has been achieved with daily supplementation of 400 mcg of folate in women of childbearing age. In addition, there is some evidence that might suggest folate reduces the risk of cardiovascular disease, certain cancers, and psychiatric disorders.

Vitamin B12 (Cobalamin) 

The major cause of clinical effects of vitamin B12 deficiency is pernicious anemia, which is caused by a lack of functional intrinsic factor in the stomach due to autoimmune destruction of gastric parietal cells. Malabsorption of food-bound vitamin B12 can also occur due to non-autoimmune atrophic gastritis, which causes loss of stomach acid and mainly affects the elderly. The hematological effects of vitamin B12 deficiency are clinically indistinguishable from those of folate deficiency causing macrocytic, or megaloblastic, anemia. Vitamin B12 deficiency can also result in impaired neurological function and increased neural tube defect risk.

Vitamin C (Ascorbic Acid)

Vitamin C deficiency is clinically and historically known as scurvy. Vitamin C deficiency is currently rare and only seen in malnourished populations with chronic conditions, poor diet, malabsorption, or substance dependency. Symptoms of vitamin C deficiency include gingival inflammation, fatigue, petechiae, bruising, and joint pain.

Vitamin A (Retinol)

Vitamin A deficiency affects 20-40 million children worldwide in regions with low-fat, plant-based diets and protein-calorie malnutrition. Vitamin A deficiency more commonly causes death than blindness in children in high-risk regions due to its role in the immune system. Vitamin A deficiency can also cause an increased risk of respiratory and diarrheal infections, decreased growth rate, slow bone development, and decreased survival from a serious illness.

Vitamin D (Cholecalciferol)

Vitamin D deficiency can lead to rickets and osteomalacia due to its critical role in bone and mineral metabolism. Rickets occurs in infants and children as a result of the failure of the bone to mineralize. The symptoms of rickets include growth retardation and bowing of the long bones of the legs. Osteomalacia occurs in adults; as a result, inadequate amounts of calcium and phosphate causing demineralization of the bone. Vitamin D may have extraskeletal effects and play a role in cardiovascular diseases, autoimmune diseases, neurological diseases, cancer, asthma, and pregnancy complications.

Vitamin E (Tocopherol)

Vitamin E deficiency is very rare but can occur in certain individuals. Symptoms of vitamin E deficiency include oxidative damage of tissues, membrane damage of cells, neurological abnormalities such as peripheral neuropathy, muscular, functional abnormalities like ataxia, and hemolytic anemia. Vitamin E deficiency most commonly occurs in premature babies of very low birthweight, people with fat-malabsorption disorders like Crohn’s disease and cystic fibrosis, and those who have a rare neurodegenerative disease called ataxia with vitamin E deficiency (AVED) that is caused by mutations in the gene for αβ-tocopherol transfer protein.

Vitamin K (Phylloquinone; Menaquinone)

Vitamin K deficiency is uncommon in healthy adults but may be seen in those with gastrointestinal malabsorptive disorders. However, newborns are at high risk for vitamin K deficiency. Newborns are at risk given milk is low in vitamin K, their stores are low since vitamin K does not pass the placenta, and their intestines are not yet populated with vitamin K synthesizing bacteria. Infants born in the United States and Canada routinely receive 0.5 to 1 mg of intramuscular phylloquinone within 6 hours of birth to prevent vitamin K deficiency bleeding, or VKDB. VKDB can affect infants up to 3 to 4 months of age and cause intracranial hemorrhage, central nervous system damage, and liver damage.

Calcium

Hypocalcemia, or calcium deficiency, can result from inadequate calcium intake, poor calcium absorption, or excessive calcium losses. Poor calcium absorption can occur due to inadequate vitamin D status. Excessive calcium losses can occur due to a lack of PTH. Symptoms of hypocalcemia can include muscle spasms, cramps, paresthesia, tetany, and seizures. Long-term hypocalcemia can impact bone health and result in reduced bone mass and osteoporosis. Hypercalcemia can occur due to increased bone resorption, increased intestinal absorption, and decreased renal excretion of calcium. Syndromes that increase PTH production can result in excessive calcium reabsorption and calcitriol production in the kidney. Excess PTH and calcitriol production can result in increased bone resorption. Excess calcitriol also can increase intestinal absorption. Symptoms of hypercalcemia include fatigue, confusion, polydipsia, frequent urination, upset stomach, bone pain, muscle weakness, and cardiac arrhythmia.

Magnesium

Magnesium deficiency, or hypomagnesemia, can occur due to chronic inadequate magnesium intake, chronic diarrhea, magnesium malabsorption, alcoholism, and medications like diuretics, antacids, proton pump inhibitors, and aminoglycoside antibiotics. Symptoms of hypomagnesemia are nonspecific and include muscle weakness, cramps, spasms, and tremors. Magnesium toxicity, or hypermagnesemia, can occur with supplemental magnesium, especially in intestinal or renal disease. Symptoms of hypermagnesemia include diarrhea, nausea, vomiting, headaches, lethargy, and flushing. At very high serum concentrations of magnesium, cardiac and electrocardiogram changes can occur, as well as coma, respiratory depression, and cardiac arrest.

Phosphorus

Phosphorus deficiency, or hypophosphatemia, is relatively rare in healthy individuals. However, hypophosphatemia can occur due to conditions that cause a shift of phosphorous from extracellular fluid to intracellular fluid, decreased intestinal absorption of phosphorus, or increased renal excretion of phosphorus. Hypophosphatemia may also occur in individuals with rare genetic disorders that decrease renal reabsorption and increase phosphorus excretion. Hypophosphatemia can appear asymptomatic until serum levels reach <1.5 mg/dL, where symptoms of anorexia, confusion, seizures, and paralysis can present. Respiratory depression can occur at serum levels <1 mg/dL. Treatment of hypophosphatemia includes oral or intravenous supplementation, depending on the severity of deficiency. Phosphorus toxicity, or hyperphosphatemia, can occur in those with chronic kidney disease due to decreased phosphorus excretion. Hyperphosphatemia is associated with increased death from cardiovascular disease due to vascular calcification in individuals with and without chronic kidney disease. Hyperphosphatemia is treated first by dietary restriction of phosphate, protein restriction, and dialysis if the latter fails. Hyperphosphatemia can also be treated with oral phosphate binders that block dietary phosphorus absorption.

Sodium

Given the pervasiveness of sodium in various foods, sodium deficiency is highly unlikely in healthy individuals. Sodium deficiency, or hyponatremia, can only occur in pathological conditions such as adrenal insufficiency, kidney disease that results in excessive sodium losses, excessive burns, diabetic ketoacidosis, and additional conditions that cause excessive sodium losses such as vomiting, diarrhea, prolonged sweating, and excessive diuretic use. Symptoms of hyponatremia include hypovalemia, lethargy, confusion, and weakness. Sodium toxicity, or hypernatremia, can occur with dehydration, hyperaldosteronemia, and renal failure. Symptoms of hypernatremia include hypervolemia, hypertension, convulsions, or coma. Even under normal conditions, continuous excessive intake of sodium can result in hypertension in certain individuals.

Potassium

Potassium is considered to be a shortfall nutrient in the American diet according to the 2010 Dietary Guidelines for American’s Advisory Committee because most Americans are unable to consume the AI of 4,700 mg/day. There is moderate evidence of an association between blood pressure reduction and potassium intake in adults, which influences cardiovascular disease risk. Hypokalemia usually occurs due to inadequate potassium intake and/or excessive potassium losses. Hypokalemia can clinically manifest in symptoms such as muscle weakness, smooth muscle dysfunction, cardiac complications, and glucose intolerance. Hyperkalemia usually occurs due to impaired renal excretion. Hyperkalemia will manifest in excitatory tissues and present symptoms such as neuromuscular symptoms such as paresthesias and fasciculations, cardiac arrest, and impaired renal function.

Chloride

Hypochloremia, or chloride deficiency, is related to clinical situations that cause excessive chloride losses due to gastrointestinal or renal conditions such as vomiting and renal failure. When serum chloride levels fall, bicarbonate reabsorption increases proportionately, resulting in metabolic alkalosis. Symptoms of hypochloremia are concurrent with those of metabolic alkalosis and include confusion, apathy, cardiac arrhythmias, and neuromuscular irritability. Hyperchloremia, or chloride toxicity, is related to clinical situations that cause excessive gastrointestinal or renal bicarbonate losses, such as severe diarrhea and medications that promote bicarbonate excretion. When serum bicarbonate levels fall, chloride reabsorption increases proportionately, resulting in metabolic acidosis.

Iron

The World Health Organization (WHO) indicates iron deficiency to be the most common form of malnutrition globally, affecting 25% of the global population. Iron deficiency is highly prevalent in both developing and developed countries. Iron deficiency is most commonly caused by inadequate dietary iron intake, inadequate iron utilization due to diseases, impaired iron absorption, or excess iron loss. Iron deficiency can often be avoided and reversed with iron supplementation and/or reducing iron losses. Untreated iron deficiency can result in microcytic anemia, poor cognitive performance, impaired immune function, impaired growth in children, poor pregnancy outcomes, and reduced endurance capacity. On the other hand, iron overload can be caused by a disease called hereditary hemochromatosis due to a C282Y mutation in the HFE gene. Hereditary hemochromatosis can be treated with iron removal therapy.

Zinc

Zinc deficiency can present clinically with symptoms such as dermatitis, alopecia, decreased appetite, frequent diarrhea, frequent upper respiratory infection, stunted growth in children, and hypogonadism. Zinc deficiency can occur due to diarrheal illness, kidney failure, and genetic diseases acrodermatitis enteropathica (AE). AE is a fatal disease of zinc malabsorption due to a mutation in the ZIP4 gene, which encodes the major intestinal zinc uptake protein. AE is treated with lifelong zinc supplementation of 100 mg/kg per day. Zinc toxicity is rare due to the tight regulation of zinc concentrations in the body. However, long-term zinc supplementation above the tolerable upper intake level of 40 mg/day can decrease copper absorption and cause copper deficiency. This occurs because zinc induced the formation of the intestinal cell protein metallothionein, which binds to metals and prevents their absorption by trapping them in the intestinal cell. Metallothionein has a stronger affinity for copper than zinc, thus trapping copper in the intestinal cell and halting absorption.

Copper

Copper deficiency generally manifests in systems such as bone marrow hematopoiesis, optic nerve function, and the nervous system. Copper deficiency causes symptoms such as fatigue and weakness. Copper deficiency can occur due to excessive zinc supplementation and the genetic disorder of copper malabsorption called Menkes disease. Menkes disease is caused by a mutation in the ATP7A gene, which causes copper to accumulate in the enterocyte, making it unable to reach the blood or any other organ system. Another genetic disease of copper metabolism is Wilson disease, which is a genetic disease of accumulation of copper mainly in the liver and the brain due to a mutation in the ATP7B gene responsible for the ATP7B exporter.

Iodine

Iodine deficiency will cause a compensatory response of the thyroid gland. When iodine intake falls below approximately 100 mcg/day, the pituitary increases secretion of TSH, which increases plasma iodine clearance by the thyroid. Thus, plasma iodine levels decrease, and thyroid hormone synthesis decreases, resulting in hypothyroidism. The increase in TSH also increases the thyroid cell number and cell size resulting in an enlarged thyroid gland or goiter. The goiter can be treated with iodine supplementation, gradually reducing the size or a thyroidectomy. If left untreated, the goiter may cause tracheal and esophageal pressure. Thyroid deficiency during pregnancy can lead to neurological cretinism in the offspring.

Selenium

Selenium deficiency has been known to appear in humans after severe and prolonged cases of selenium deprivation. Selenium deficiency is known as Keshan disease and occurs in areas where selenium content in the soil is low, like China. Symptoms of Keshan disease include cardiomyopathy, peripheral myopathy, decreased muscle tone and function, hair thinning, opacification of nails, and anemia.

References

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Seeds – Which Seeds Contain How Much Vitamin

Which Seeds Contain How Much Vitamin/Seeds contain all the starting materials necessary to develop into complex plants. Because of this, they are extremely nutritious. Seeds are great sources of fiber. They also contain healthy monounsaturated fats, polyunsaturated fats and many important vitamins, minerals, and antioxidants. When consumed as part of a healthy diet, seeds can help reduce blood sugar, cholesterol, and blood pressure.

This article will describe the nutritional content and health benefits of six of the healthiest seeds you can eat.

1. Flaxseeds

Flaxseeds, also known as linseeds, are a great source of fiber and omega-3 fats, particularly alpha-linolenic acid (ALA). However, the omega-3 fats are contained within the fibrous outer shell of the seed, which humans can’t digest easily. Therefore, if you want to increase your omega-3 levels, it’s best to eat flaxseeds that have been ground (rx,rx).

A 1-ounce (28-gram) serving of flaxseeds contains a wide mix of nutrients (rx):

  • Calories: 152
  • Fiber: 7.8 grams
  • Protein: 5.2 grams
  • Monounsaturated fat: 2.1 grams
  • Omega-3 fats: 6.5 grams
  • Omega-6 fats: 1.7 grams
  • Manganese: 35% of the RDI
  • Thiamine (vitamin B1): 31% of the RDI
  • Magnesium: 28% of the RDI

Flaxseeds also contain a number of different polyphenols, especially lignans, which act as important antioxidants in the body (rx).

Lignans, as well as the fiber and omega-3 fats in flaxseeds, can all help reduce cholesterol and other risk factors for heart disease (rx,rx,rx).

One large study combined the results of 28 others, finding that consuming flaxseeds reduced levels of “bad” LDL cholesterol by an average of 10 mmol/l (rx).

Flaxseeds may also help reduce blood pressure. An analysis of 11 studies found that flaxseeds could reduce blood pressure especially when eaten whole every day for more than 12 weeks (rx).

A couple of studies have shown that eating flaxseeds may reduce markers of tumor growth in women with breast cancer, and may also reduce cancer risk (rx, rx, rx).

This may be due to the lignans in flaxseeds. Lignans are phytoestrogens and are similar to the female sex hormone estrogen.

What’s more, similar benefits have been shown regarding prostate cancer in men (rx).

In addition to reducing the risk of heart disease and cancer, flaxseeds may also help reduce blood sugar,                                 which may help lower the risk of diabetes (rx). Flaxseeds are an excellent source of fiber, omega-3 fats,                                   lignans and other nutrients. A lot of evidence has shown they may reduce cholesterol, blood pressure and                                even the risk of cancer.

2. Chia Seeds

Chia seeds are very similar to flaxseeds because they are also good sources of fiber and omega-3 fats, along with a number of other nutrients.

A 1-ounce (28-gram) serving of chia seeds contains (rx):

  • Calories: 137
  • Fiber: 10.6 grams
  • Protein: 4.4 grams
  • Monounsaturated fat: 0.6 grams
  • Omega-3 fats: 4.9 grams
  • Omega-6 fats: 1.6 grams
  • Thiamine (vitamin B1): 15% of the RDI
  • Magnesium: 30% of the RDI
  • Manganese: 30% of the RDI

Like flaxseeds, chia seeds also contain a number of important antioxidant polyphenols.

Interestingly, a number of studies have shown that eating chia seeds can increase ALA in the blood. ALA is an important omega-3 fatty acid that can help reduce inflammation (rx, rx).

Your body can convert ALA into other omega-3 fats, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are the omega-3 fats found in oily fish. However, this conversion process in the body is usually quite inefficient.

One study has shown that chia seeds may be able to increase levels of EPA in the blood (rx).

Chia seeds may also help reduce blood sugar. A couple of studies have shown that whole and ground chia seeds are equally effective for reducing blood sugar immediately after a meal (rx, rx).

Another study found that, as well as reducing blood sugar, chia seeds may reduce appetite (rx).

Chia seeds may also reduce risk factors of heart disease (rx).

A study of 20 people with type 2 diabetes found that eating 37 grams of chia seeds per day for 12 weeks reduced blood pressure and levels of several inflammatory chemicals, including C-reactive protein (CRP) (rx).

SUMMARY:Chia seeds are a good source of omega-3 fats and are effective at lowering blood sugar and reducing risk factors for heart disease.

3. Hemp Seeds

Hemp seeds are an excellent source of vegetarian protein. In fact, they contain more than 30% protein, as well as many other essential nutrients.

Hemp seeds are one of the few plants that are complete protein sources, meaning they contain all the essential amino acids that your body can’t make.

Studies have also shown that the protein quality of hemp seeds is better than most other plant protein sources (rx).

A 1-ounce (28-gram) serving of hemp seeds contains (rx):

  • Calories: 155
  • Fiber: 1.1 grams
  • Protein: 8.8 grams
  • Monounsaturated fat: 0.6 grams
  • Polyunsaturated fat: 10.7 grams
  • Magnesium: 45% of the RDI
  • Thiamine (vitamin B1): 31% of the RDI
  • Zinc: 21% of the RDI

The proportion of omega-6 to omega-3 fats in hemp seed oil is roughly 3:1, which is considered a good ratio. Hemp seeds also contain gamma-linolenic acid, an important anti-inflammatory fatty acid (rx).

For this reason, many people take hemp seed oil supplements.

Hemp seed oil may have a beneficial effect on heart health by increasing the amount of omega-3 fatty acids in the blood (rx, rx, erx).

The anti-inflammatory action of the omega-3 fatty acids may also help improve symptoms of eczema.

One study found that people with eczema experienced less skin dryness and itchiness after taking hemp seed oil supplements for 20 weeks. They also used skin medication less, on average (rx).

SUMMARY:Hemp seeds are a great source of protein and contain all the essential amino acids. Hemp seed oil may help reduce symptoms of eczema and other chronic inflammatory conditions.

4. Sesame seeds

Sesame seeds are commonly consumed in Asia, and also in Western countries as part of a paste called tahini.

Similar to other seeds, they contain a wide nutrient profile. One ounce (28 grams) of sesame seeds contains (rx):

  • Calories: 160
  • Fiber: 3.3 grams
  • Protein: 5 grams
  • Monounsaturated fat: 5.3 grams
  • Omega-6 fats: 6 grams
  • Copper: 57% of the RDI
  • Manganese: 34% of the RDI
  • Magnesium: 25% of the RDI

Like flaxseeds, sesame seeds contain a lot of lignans, particularly one called sesamin. In fact, sesame seeds are the best known dietary source of lignans.

A couple of interesting studies have shown that sesamin from sesame seeds may get converted by your gut bacteria into another type of lignan called enterolactone (rx, rx).

Enterolactone can act like the sex hormone estrogen, and lower-than-normal levels of this lignan in the body have been associated with heart disease and breast cancer (rx).

Another study found that postmenopausal women who ate 50 grams of sesame seed powder daily for five weeks had significantly lower blood cholesterol and improved sex hormone status (rx).

Sesame seeds may also help reduce inflammation and oxidative stress, which can worsen symptoms of many disorders, including arthritis.

One study showed that people with knee osteoarthritis had significantly fewer inflammatory chemicals in their blood after eating about 40 grams of sesame seed powder every day for two months (rx).

Another recent study found that after eating about 40 grams of sesame seed powder per day for 28 days, semi-professional athletes had significantly reduced muscle damage and oxidative stress, as well as increased aerobic capacity (rx).

SUMMARY:Sesame seeds are a great source of lignans, which may help improve sex hormone status for estrogen. Sesame seeds may also help reduce inflammation and oxidative stress.

5. Pumpkin Seeds

Pumpkin seeds are one of the most commonly consumed types of seeds, and are good sources of phosphorus, monounsaturated fats and omega-6 fats.

A 1-ounce (28-gram) serving of pumpkin seeds contains (rx):

  • Calories: 151
  • Fiber: 1.7 grams
  • Protein: 7 grams
  • Monounsaturated fat: 4 grams
  • Omega-6 fats: 6 grams
  • Manganese: 42% of the RDI
  • Magnesium: 37% of the RDI
  • Phosphorus: 33% of the RDI

Pumpkin seeds are also good sources of phytosterols, which are plant compounds that may help lower blood cholesterol (rx).

These seeds have been reported to have a number of health benefits, likely due to their wide range of nutrients.

One observational study of more than 8,000 people found that those who had a higher intake of pumpkin and sunflower seeds had a significantly reduced risk of breast cancer (rx).

Another study in children found that pumpkin seeds may help lower the risk of bladder stones by reducing the amount of calcium in urine (rx).

Bladder stones are similar to kidney stones. They’re formed when certain minerals crystalize inside the bladder, which leads to abdominal discomfort.

A couple of studies have shown that pumpkin seed oil can improve symptoms of prostate and urinary disorders (rx, rx).

These studies also showed that pumpkin seed oil may reduce symptoms of overactive bladder and improve quality of life for men with enlarged prostates.

A study of postmenopausal women also found that pumpkin seed oil may help reduce blood pressure, increase “good” HDL cholesterol and improve menopause symptoms (rx).

SUMMARY:Pumpkin seeds and pumpkin seed oil are good sources of monounsaturated and omega-6 fats, and may help improve heart health and symptoms of urinary disorders.

Sunflower seeds contain a good amount of protein, monounsaturated fats and vitamin E. One ounce (28 grams) of sunflower seeds contains (rx):

  • Calories: 164
  • Fiber: 2.4 grams
  • Protein: 5.8 grams
  • Monounsaturated fat: 5.2 grams
  • Omega-6 fats: 6.4 grams
  • Vitamin E: 47% of the RDI
  • Manganese: 27% of the RDI
  • Magnesium: 23% of the RDI

Sunflower seeds may be associated with reduced inflammation in middle-aged and older people, which may help reduce the risk of heart disease.

An observational study of more than 6,000 adults found that a high intake of nuts and seeds was associated with reduced inflammation (rx).

In particular, consuming sunflower seeds more than five times per week was associated with reduced levels of C-reactive protein (CRP), a key chemical involved in inflammation.

Another study examined whether eating nuts and seeds affected blood cholesterol levels in postmenopausal women with type 2 diabetes (rx).

The women consumed 30 grams of sunflower seeds or almonds as part of a healthy diet every day for three weeks.

By the end of the study, both the almond and sunflower seed groups had experienced reduced total cholesterol and LDL cholesterol. The sunflower seed diet reduced triglycerides in the blood more than the almond diet, though.

However, “good” HDL cholesterol was also reduced, suggesting that sunflower seeds may reduce both good and bad types of cholesterol.

SUMMARY:Sunflower seeds contain high levels of both monounsaturated and omega-6 fats, and may help reduce inflammation and cholesterol levels.

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The 17 Best Protein Sources for Vegans and Vegetarians

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A common concern about vegetarian and vegan diets is that they might lack sufficient protein.

However, many experts agree that a well-planned vegetarian or vegan diet can provide you with all the nutrients you need (rx, rx, rx, rx).

That said, certain plant foods contain significantly more protein than others.

And higher-protein diets can promote muscle strength, satiety and weight loss (rx, rx, rx).

Here are 17 plant foods that contain a high amount of protein per serving.

1. Seitan

Seitan is a popular protein source for many vegetarians and vegans.

It’s made from gluten, the main protein in wheat. Unlike many soy-based mock meats, it resembles the look and texture of meat when cooked.

Also known as wheat meat or wheat gluten, it contains about 25 grams of protein per 3.5 ounces (100 grams). This makes it the richest plant protein source on this list (rx).

Seitan is also a good source of selenium and contains small amounts of iron, calcium and phosphorus (rx).

You can find this meat alternative in the refrigerated section of most health food stores, or make your own version with vital wheat gluten using this recipe.

Seitan can be pan-fried, sautéed and even grilled. Therefore, it can be easily incorporated in a variety of recipes.

However, seitan should be avoided by people with celiac disease or gluten sensitivity.

BOTTOM LINE:Seitan is a mock meat made from wheat gluten. Its high protein content, meat-like texture and versatility make it a popular plant-based protein choice among many vegetarians and vegans.

2. Tofu, Tempeh and Edamame

Tofu, tempeh and edamame all originate from soybeans.

Soybeans are considered a whole source of protein. This means that they provide the body with all the essential amino acids it needs.

Edamame are immature soybeans with a sweet and slightly grassy taste. They need to be steamed or boiled prior to consumption and can be eaten on their own or added to soups and salads.

Tofu is made from bean curds pressed together in a process similar to cheesemaking. Tempeh is made by cooking and slightly fermenting mature soybeans prior to pressing them into a patty.

Tofu doesn’t have much taste, but easily absorbs the flavor of the ingredients it’s prepared with. Comparatively, tempeh has a characteristic nutty flavor.

Both tofu and tempeh can be used in a variety of recipes, ranging from burgers to soups and chilis.

All three contain iron, calcium and 10-19 grams of protein per 3.5 ounces (100 grams) (rx, rx, rx).

Edamame are also rich in folate, vitamin K and fiber. Tempeh contains a good amount of probiotics, B vitamins and minerals such as magnesium and phosphorus.

BOTTOM LINE:Tofu, tempeh and edamame all originate from soybeans, a complete source of protein. They also contain good amounts of several other nutrients and can be used in a variety of recipes.

3. Lentils

At 18 grams of protein per cooked cup (240 ml), lentils are a great source of protein (rx).

They can be used in a variety of dishes, ranging from fresh salads to hearty soups and spice-infused dahls.

Lentils also contain good amounts of slowly digested carbs, and a single cup (240 ml) provides approximately 50% of your recommended daily fiber intake.

Furthermore, the type of fiber found in lentils has been shown to feed the good bacteria in your colon, promoting a healthy gut. Lentils may also help reduce the risk of heart disease, diabetes, excess body weight and some types of cancer (rx).

In addition, lentils are rich in folate, manganese and iron. They also contain a good amount of antioxidants and other health-promoting plant compounds (rx).

BOTTOM LINE:Lentils are nutritional powerhouses. They are rich in protein and contain good amounts of other nutrients. They may also help reduce the risk of various diseases.

4. Chickpeas and Most Varieties of Beans

Kidney, black, pinto and most other varieties of beans contain high amounts of protein per serving.

Chickpeas, also known as garbanzo beans, are another legume with high protein content.

Both beans and chickpeas contain about 15 grams of protein per cooked cup (240 ml). They are also excellent sources of complex carbs, fiber, iron, folate, phosphorus, potassium, manganese, and several beneficial plant compounds (rx, rx, rx).

Moreover, several studies show that a diet rich in beans and other legumes can decrease cholesterol, help control blood sugar levels, lower blood pressure and even reduce belly fat (rx, rx, rx,rx).

Add beans to your diet by making a tasty bowl of homemade chili, or enjoy extra health benefits by sprinkling a dash of turmeric on roasted chickpeas (rx).

BOTTOM LINE:Beans are health-promoting, protein-packed legumes that contain a variety of vitamins, minerals and beneficial plant compounds.

5. Nutritional Yeast

Nutritional yeast is a deactivated strain of Saccharomyces cerevisiae yeast, sold commercially as a yellow powder or flakes.

It has a cheesy flavor, which makes it a popular ingredient in dishes like mashed potatoes and scrambled tofu.

Nutritional yeast can also be sprinkled on top of pasta dishes or even enjoyed as a savory topping on popcorn.

This complete source of plant protein provides the body with 14 grams of protein and 7 grams of fiber per ounce (28 grams) (rx).

Fortified nutritional yeast is also an excellent source of zinc, magnesium, copper, manganese and all the B vitamins, including B12 (rx).

However, fortification is not universal and unfortified nutritional yeast should not be relied on as a source of vitamin B12.

BOTTOM LINE:Nutritional yeast is a popular plant-based ingredient often used to give dishes a dairy-free cheese flavor. It is high in protein, fiber and is often fortified with various nutrients, including vitamin B12.

6. Spelt and Teff

Spelled and teff belong to a category known as ancient grains. Other ancient grains include einkorn, barley, sorghum, and farro.

Spelled is a type of wheat and contains gluten, whereas teff originates from an annual grass, which means it’s gluten-free.

Spelled and teff provide 10–11 grams of protein per cooked cup (240 ml), making them higher in protein than other ancient grains (rx, rx).

Both are excellent sources of various nutrients, including complex carbs, fiber, iron, magnesium, phosphorus, and manganese. They also contain good amounts of B vitamins, zinc, and selenium.

Spelled and teff are versatile alternatives to common grains, such as wheat and rice, and can be used in many recipes ranging from baked goods to polenta and risotto.

You can purchase spelled and teff online.

BOTTOM LINE:Spelt and teff are high-protein ancient grains. They’re a great source of various vitamins and minerals and an interesting alternative to more common grains.

7. Hempseed

Hempseed comes from the Cannabis sativa plant, which is notorious for belonging to the same family as the marijuana plant.

But hempseed contains only trace amounts of THC, the compound that produces the marijuana-like drug effects.

Although not as well-known as other seeds, hempseed contains 10 grams of complete, easily digestible protein per ounce (28 grams). That’s 50% more than chia seeds and flaxseeds (rx, rx).

Hempseed also contains a good amount of magnesium, iron, calcium, zinc and selenium. What’s more, it’s a good source of omega-3 and omega-6 fatty acids in the ratio considered optimal for human health (rx).

Interestingly, some studies indicate that the type of fats found in hempseed may help reduce inflammation, as well as diminish symptoms of PMS, menopause, and certain skin diseases (rx, rx, rx, rx, rx).

You can add hemp seed to your diet by sprinkling some in your smoothie or morning muesli. It can also be used in homemade salad dressings or protein bars.

BOTTOM LINE:Hempseed contains a good amount of complete, highly-digestible protein, as well as health-promoting essential fatty acids in a ratio optimal for human health

8. Green Peas

The little green peas often served as a side dish contain 9 grams of protein per cooked cup (240 ml), which is slightly more than a cup of milk (rx).

What’s more, a serving of green peas covers more than 25% of your daily fiber, vitamin A, C, K, thiamine, folate, and manganese requirements.

Green peas are also a good source of iron, magnesium, phosphorus, zinc, copper and several other B vitamins (rx).

You can use peas in recipes such as pea and basil stuffed ravioli, thai-inspired pea soup or pea and avocado guacamole.

BOTTOM LINE:Green peas are high in protein, vitamins and minerals and can be used as more than just a side dish.

9. Spirulina

This blue-green algae is definitely a nutritional powerhouse.

Two tablespoons (30 ml) provide you with 8 grams of complete protein, in addition to covering 22% of your daily requirements of iron and thiamin and 42% of your daily copper needs (rx).

Spirulina also contains decent amounts of magnesium, riboflavin, manganese, potassium and small amounts of most of the other nutrients your body needs, including essential fatty acids.

Phycocyanin, a natural pigment found in spirulina, appears to have powerful antioxidant, anti-inflammatory and anti-cancer properties (rx, rx, rx).

Furthermore, studies link consuming spirulina to health benefits ranging from a stronger immune system and reduced blood pressure to improved blood sugar and cholesterol levels (rx, rx, rx, rx).

BOTTOM LINE:Spirulina is a nutritious high-protein food with many beneficial health-enhancing properties.

10. Amaranth and Quinoa

Although often referred to as ancient or gluten-free grains, amaranth and quinoa don’t grow from grasses like other cereal grains do.

For this reason, they’re technically considered “pseudocereals.”

Nevertheless, they can be prepared or ground into flours similar to more commonly known grains.

Amaranth and quinoa provide 8–9 grams of protein per cooked cup (240 ml) and are complete sources of protein, which is rare among grains and pseudocereals (rx, rx).

Also, amaranth and quinoa are good sources of complex carbs, fiber, iron, manganese, phosphorus and magnesium (rx, rx).

BOTTOM LINE:Amaranth and quinoa are pseudocereals that provide you with a complete source of protein. They can be prepared and eaten similar to traditional grains such as wheat and rice.

11. Ezekiel Bread and Other Bread Made From Sprouted Grains

Ezekiel bread is made from organic, sprouted whole grains and legumes. These include wheat, millet, barley, and spelt, as well as soybeans and lentils.

Two slices of Ezekiel bread contain approximately 8 grams of protein, which is slightly more than the average bread (rx).

Sprouting grains and legumes increases the number of healthy nutrients they contain and reduces the number of anti-nutrients in them (rx, rx).

In addition, studies show that sprouting increases their amino acid content. Lysine is the limiting amino acid in many plants, and sprouting increases the lysine content. This helps boost the overall protein quality (rx).

Similarly, combining grains with legumes could further improve the bread’s amino acid profile (rx).

Sprouting also seems to increase the bread’s soluble fiber, folate, vitamin C, vitamin E and beta-carotene content. It may also slightly reduce the gluten content, which can enhance digestion in those sensitive to gluten (rx, rx).

BOTTOM LINE:Ezekiel and other breads made from sprouted grains have an enhanced protein and nutrient profile, compared to more traditional breads.

12. Soy Milk

Milk that’s made from soybeans and fortified with vitamins and minerals is a great alternative to cow’s milk.

Not only does it contain 7 grams of protein per cup (240 ml), but it’s also an excellent source of calcium, vitamin D and vitamin B12 (rx).

However, keep in mind that soy milk and soybeans do not naturally contain vitamin B12, so picking a fortified variety is recommended.

Soy milk is found in most supermarkets. It’s an incredibly versatile product that can be consumed on its own or in a variety of cooking and baking recipes.

It is a good idea to opt for unsweetened varieties to keep the amount of added sugars to a minimum.

BOTTOM LINE:Soy milk is a high-protein plant alternative to cow’s milk. It’s a versatile product that can be used in a variety of ways.

13. Oats and Oatmeal

Oats are an easy and delicious way to add protein to any diet.

Half a cup (120 ml) of dry oats provides you with approximately 6 grams of protein and 4 grams of fiber. This portion also contains good amounts of magnesium, zinc, phosphorus and folate (rx).

Although oats are not considered a complete protein, they do contain higher-quality protein than other commonly consumed grains like rice and wheat.

You can use oats in a variety of recipes ranging from oatmeal to veggie burgers. They can also be ground into flour and used for baking.

BOTTOM LINE:Oats are not only nutritious but also an easy and delicious way to incorporate plant protein into a vegan or vegetarian diet.

14. Wild Rice

Wild rice contains approximately 1.5 times as much protein as other long-grain rice varieties, including brown rice and basmati.

One cooked cup (240 ml) provides 7 grams of protein, in addition to a good amount of fiber, manganese, magnesium, copper, phosphorus and B vitamins (rx).

Unlike white rice, wild rice is not stripped of its bran. This is great from a nutritional perspective, as bran contains fiber and plenty of vitamins and minerals (rx).

However, this causes concerns about arsenic, which can accumulate in the bran of rice crops grown in polluted areas.

Arsenic is a toxic trace element that may give rise to various health problems, especially when ingested regularly for long periods of time (rx, rx,rx, rx).

Washing wild rice before cooking and using plenty of water to boil it may reduce the arsenic content by up to 57% (rx).

BOTTOM LINE:Wild rice is a tasty, nutrient-rich plant source of protein. Those relying on wild rice as a food staple should take precautions to reduce its arsenic content.

15. Chia Seeds

Chia seeds are derived from the Salvia hispanica plant, which is native to Mexico and Guatemala.

At 6 grams of protein and 13 grams of fiber per 1.25 ounces (35 grams), chia seeds definitely deserve their spot on this list (rx).

What’s more, these little seeds contain a good amount of iron, calcium, selenium and magnesium, as well as omega-3 fatty acids, antioxidants, and various other beneficial plant compounds (rx, rx).

They’re also incredibly versatile. Chia seeds have a bland taste and are able to absorb water, turning into a gel-like substance. This makes them an easy addition to a variety of recipes, ranging from smoothies to baked goods and chia puddings.

BOTTOM LINE:Chia seeds are a versatile source of plant protein. They also contain a variety of vitamins, minerals, antioxidants and other health-promoting compounds.

16. Nuts, Nut Butters, and Other Seeds

Nuts, seeds and their derived products are great sources of protein.

One ounce (28 grams) contains between 5–7 grams of protein, depending on the nut and seed variety (rx, rx, rx, rx, rx, rx).

Nuts and seeds are also great sources of fiber and healthy fats, in addition to iron, calcium, magnesium, selenium, phosphorus, vitamin E and certain B vitamins. They also contain antioxidants, among other beneficial plant compounds (rx).

When choosing which nuts and seeds to buy, keep in mind that blanching and roasting may damage the nutrients in nuts. So reach for raw, unblanched versions whenever possible (rx).

Also, try opting for natural nut butter to avoid the oil, sugar and excess salt often added to many household brand varieties.

BOTTOM LINE:Nuts, seeds and their butters are an easy way to add plant protein, vitamins and minerals to your diet. Opt to consume them raw, unblanched and with no other additives to maximize their nutrient content.

17. Protein-Rich Fruits and Vegetables

All fruits and vegetables contain protein, but the amounts are usually small.

However, some contain more than others.

Vegetables with the most protein include broccoli, spinach, asparagus, artichokes, potatoes, sweet potatoes and Brussels sprouts. They contain about 4–5 grams of protein per cooked cup (rx, rx, rx, rx, rx, rx, rx). Although technically a grain, sweet corn is a common food that contains about as much protein as these high-protein vegetables (rx).

Fresh fruits generally have a lower protein content than vegetables. Those containing the most include guava, cherimoyas, mulberries, blackberries, nectarines and bananas, which have about 2–4 grams of protein per cup (rx, rx, rx, ez, rx, rx).

BOTTOM LINE:Certain fruits and vegetables contain more protein than others. Include them in your meals to increase your daily protein intake.

Take-Home Message

Protein deficiencies among vegetarians and vegans are far from being the norm (rx). Nonetheless, some people may be interested in increasing their plant protein intake for a variety of reasons. This list can be used as a guide for anyone interested in incorporating more plant-based proteins into their diet.

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Top Best Super Healthy Seeds You Should Eat for Good Health

Seeds contain all the starting materials necessary to develop into complex plants. Because of this, they are extremely nutritious. Seeds are great sources of fiber. They also contain healthy monounsaturated fats, polyunsaturated fats and many important vitamins, minerals, and antioxidants. When consumed as part of a healthy diet, seeds can help reduce blood sugar, cholesterol, and blood pressure.

This article will describe the nutritional content and health benefits of six of the healthiest seeds you can eat.

1. Flaxseeds

Flaxseeds, also known as linseeds, are a great source of fiber and omega-3 fats, particularly alpha-linolenic acid (ALA). However, the omega-3 fats are contained within the fibrous outer shell of the seed, which humans can’t digest easily. Therefore, if you want to increase your omega-3 levels, it’s best to eat flaxseeds that have been ground (rx,rx).

A 1-ounce (28-gram) serving of flaxseeds contains a wide mix of nutrients (rx):

  • Calories: 152
  • Fiber: 7.8 grams
  • Protein: 5.2 grams
  • Monounsaturated fat: 2.1 grams
  • Omega-3 fats: 6.5 grams
  • Omega-6 fats: 1.7 grams
  • Manganese: 35% of the RDI
  • Thiamine (vitamin B1): 31% of the RDI
  • Magnesium: 28% of the RDI

Flaxseeds also contain a number of different polyphenols, especially lignans, which act as important antioxidants in the body (rx).

Lignans, as well as the fiber and omega-3 fats in flaxseeds, can all help reduce cholesterol and other risk factors for heart disease (rx,rx,rx).

One large study combined the results of 28 others, finding that consuming flaxseeds reduced levels of “bad” LDL cholesterol by an average of 10 mmol/l (rx).

Flaxseeds may also help reduce blood pressure. An analysis of 11 studies found that flaxseeds could reduce blood pressure especially when eaten whole every day for more than 12 weeks (rx).

A couple of studies have shown that eating flaxseeds may reduce markers of tumor growth in women with breast cancer, and may also reduce cancer risk (rx, rx, rx).

This may be due to the lignans in flaxseeds. Lignans are phytoestrogens and are similar to the female sex hormone estrogen.

What’s more, similar benefits have been shown regarding prostate cancer in men (rx).

In addition to reducing the risk of heart disease and cancer, flaxseeds may also help reduce blood sugar,                                 which may help lower the risk of diabetes (rx). Flaxseeds are an excellent source of fiber, omega-3 fats,                                   lignans and other nutrients. A lot of evidence has shown they may reduce cholesterol, blood pressure and                                even the risk of cancer.

2. Chia Seeds

Chia seeds are very similar to flaxseeds because they are also good sources of fiber and omega-3 fats, along with a number of other nutrients.

A 1-ounce (28-gram) serving of chia seeds contains (rx):

  • Calories: 137
  • Fiber: 10.6 grams
  • Protein: 4.4 grams
  • Monounsaturated fat: 0.6 grams
  • Omega-3 fats: 4.9 grams
  • Omega-6 fats: 1.6 grams
  • Thiamine (vitamin B1): 15% of the RDI
  • Magnesium: 30% of the RDI
  • Manganese: 30% of the RDI

Like flaxseeds, chia seeds also contain a number of important antioxidant polyphenols.

Interestingly, a number of studies have shown that eating chia seeds can increase ALA in the blood. ALA is an important omega-3 fatty acid that can help reduce inflammation (rx, rx).

Your body can convert ALA into other omega-3 fats, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are the omega-3 fats found in oily fish. However, this conversion process in the body is usually quite inefficient.

One study has shown that chia seeds may be able to increase levels of EPA in the blood (rx).

Chia seeds may also help reduce blood sugar. A couple of studies have shown that whole and ground chia seeds are equally effective for reducing blood sugar immediately after a meal (rx, rx).

Another study found that, as well as reducing blood sugar, chia seeds may reduce appetite (rx).

Chia seeds may also reduce risk factors of heart disease (rx).

A study of 20 people with type 2 diabetes found that eating 37 grams of chia seeds per day for 12 weeks reduced blood pressure and levels of several inflammatory chemicals, including C-reactive protein (CRP) (rx).

SUMMARY:Chia seeds are a good source of omega-3 fats and are effective at lowering blood sugar and reducing risk factors for heart disease.

3. Hemp Seeds

Hemp seeds are an excellent source of vegetarian protein. In fact, they contain more than 30% protein, as well as many other essential nutrients.

Hemp seeds are one of the few plants that are complete protein sources, meaning they contain all the essential amino acids that your body can’t make.

Studies have also shown that the protein quality of hemp seeds is better than most other plant protein sources (rx).

A 1-ounce (28-gram) serving of hemp seeds contains (rx):

  • Calories: 155
  • Fiber: 1.1 grams
  • Protein: 8.8 grams
  • Monounsaturated fat: 0.6 grams
  • Polyunsaturated fat: 10.7 grams
  • Magnesium: 45% of the RDI
  • Thiamine (vitamin B1): 31% of the RDI
  • Zinc: 21% of the RDI

The proportion of omega-6 to omega-3 fats in hemp seed oil is roughly 3:1, which is considered a good ratio. Hemp seeds also contain gamma-linolenic acid, an important anti-inflammatory fatty acid (rx).

For this reason, many people take hemp seed oil supplements.

Hemp seed oil may have a beneficial effect on heart health by increasing the amount of omega-3 fatty acids in the blood (rx, rx, erx).

The anti-inflammatory action of the omega-3 fatty acids may also help improve symptoms of eczema.

One study found that people with eczema experienced less skin dryness and itchiness after taking hemp seed oil supplements for 20 weeks. They also used skin medication less, on average (rx).

SUMMARY:Hemp seeds are a great source of protein and contain all the essential amino acids. Hemp seed oil may help reduce symptoms of eczema and other chronic inflammatory conditions.

4. Sesame seeds

Sesame seeds are commonly consumed in Asia, and also in Western countries as part of a paste called tahini.

Similar to other seeds, they contain a wide nutrient profile. One ounce (28 grams) of sesame seeds contains (rx):

  • Calories: 160
  • Fiber: 3.3 grams
  • Protein: 5 grams
  • Monounsaturated fat: 5.3 grams
  • Omega-6 fats: 6 grams
  • Copper: 57% of the RDI
  • Manganese: 34% of the RDI
  • Magnesium: 25% of the RDI

Like flaxseeds, sesame seeds contain a lot of lignans, particularly one called sesamin. In fact, sesame seeds are the best known dietary source of lignans.

A couple of interesting studies have shown that sesamin from sesame seeds may get converted by your gut bacteria into another type of lignan called enterolactone (rx, rx).

Enterolactone can act like the sex hormone estrogen, and lower-than-normal levels of this lignan in the body have been associated with heart disease and breast cancer (rx).

Another study found that postmenopausal women who ate 50 grams of sesame seed powder daily for five weeks had significantly lower blood cholesterol and improved sex hormone status (rx).

Sesame seeds may also help reduce inflammation and oxidative stress, which can worsen symptoms of many disorders, including arthritis.

One study showed that people with knee osteoarthritis had significantly fewer inflammatory chemicals in their blood after eating about 40 grams of sesame seed powder every day for two months (rx).

Another recent study found that after eating about 40 grams of sesame seed powder per day for 28 days, semi-professional athletes had significantly reduced muscle damage and oxidative stress, as well as increased aerobic capacity (rx).

SUMMARY:Sesame seeds are a great source of lignans, which may help improve sex hormone status for estrogen. Sesame seeds may also help reduce inflammation and oxidative stress.

5. Pumpkin Seeds

Pumpkin seeds are one of the most commonly consumed types of seeds, and are good sources of phosphorus, monounsaturated fats and omega-6 fats.

A 1-ounce (28-gram) serving of pumpkin seeds contains (rx):

  • Calories: 151
  • Fiber: 1.7 grams
  • Protein: 7 grams
  • Monounsaturated fat: 4 grams
  • Omega-6 fats: 6 grams
  • Manganese: 42% of the RDI
  • Magnesium: 37% of the RDI
  • Phosphorus: 33% of the RDI

Pumpkin seeds are also good sources of phytosterols, which are plant compounds that may help lower blood cholesterol (rx).

These seeds have been reported to have a number of health benefits, likely due to their wide range of nutrients.

One observational study of more than 8,000 people found that those who had a higher intake of pumpkin and sunflower seeds had a significantly reduced risk of breast cancer (rx).

Another study in children found that pumpkin seeds may help lower the risk of bladder stones by reducing the amount of calcium in urine (rx).

Bladder stones are similar to kidney stones. They’re formed when certain minerals crystalize inside the bladder, which leads to abdominal discomfort.

A couple of studies have shown that pumpkin seed oil can improve symptoms of prostate and urinary disorders (rx, rx).

These studies also showed that pumpkin seed oil may reduce symptoms of overactive bladder and improve quality of life for men with enlarged prostates.

A study of postmenopausal women also found that pumpkin seed oil may help reduce blood pressure, increase “good” HDL cholesterol and improve menopause symptoms (rx).

SUMMARY:Pumpkin seeds and pumpkin seed oil are good sources of monounsaturated and omega-6 fats, and may help improve heart health and symptoms of urinary disorders.

Sunflower seeds contain a good amount of protein, monounsaturated fats and vitamin E. One ounce (28 grams) of sunflower seeds contains (rx):

  • Calories: 164
  • Fiber: 2.4 grams
  • Protein: 5.8 grams
  • Monounsaturated fat: 5.2 grams
  • Omega-6 fats: 6.4 grams
  • Vitamin E: 47% of the RDI
  • Manganese: 27% of the RDI
  • Magnesium: 23% of the RDI

Sunflower seeds may be associated with reduced inflammation in middle-aged and older people, which may help reduce the risk of heart disease.

An observational study of more than 6,000 adults found that a high intake of nuts and seeds was associated with reduced inflammation (rx).

In particular, consuming sunflower seeds more than five times per week was associated with reduced levels of C-reactive protein (CRP), a key chemical involved in inflammation.

Another study examined whether eating nuts and seeds affected blood cholesterol levels in postmenopausal women with type 2 diabetes (rx).

The women consumed 30 grams of sunflower seeds or almonds as part of a healthy diet every day for three weeks.

By the end of the study, both the almond and sunflower seed groups had experienced reduced total cholesterol and LDL cholesterol. The sunflower seed diet reduced triglycerides in the blood more than the almond diet, though.

However, “good” HDL cholesterol was also reduced, suggesting that sunflower seeds may reduce both good and bad types of cholesterol.

SUMMARY:Sunflower seeds contain high levels of both monounsaturated and omega-6 fats, and may help reduce inflammation and cholesterol levels.

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The 17 Best Protein Sources for Vegans and Vegetarians

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A common concern about vegetarian and vegan diets is that they might lack sufficient protein.

However, many experts agree that a well-planned vegetarian or vegan diet can provide you with all the nutrients you need (rx, rx, rx, rx).

That said, certain plant foods contain significantly more protein than others.

And higher-protein diets can promote muscle strength, satiety and weight loss (rx, rx, rx).

Here are 17 plant foods that contain a high amount of protein per serving.

1. Seitan

Seitan is a popular protein source for many vegetarians and vegans.

It’s made from gluten, the main protein in wheat. Unlike many soy-based mock meats, it resembles the look and texture of meat when cooked.

Also known as wheat meat or wheat gluten, it contains about 25 grams of protein per 3.5 ounces (100 grams). This makes it the richest plant protein source on this list (rx).

Seitan is also a good source of selenium and contains small amounts of iron, calcium and phosphorus (rx).

You can find this meat alternative in the refrigerated section of most health food stores, or make your own version with vital wheat gluten using this recipe.

Seitan can be pan-fried, sautéed and even grilled. Therefore, it can be easily incorporated in a variety of recipes.

However, seitan should be avoided by people with celiac disease or gluten sensitivity.

BOTTOM LINE:Seitan is a mock meat made from wheat gluten. Its high protein content, meat-like texture and versatility make it a popular plant-based protein choice among many vegetarians and vegans.

2. Tofu, Tempeh and Edamame

Tofu, tempeh and edamame all originate from soybeans.

Soybeans are considered a whole source of protein. This means that they provide the body with all the essential amino acids it needs.

Edamame are immature soybeans with a sweet and slightly grassy taste. They need to be steamed or boiled prior to consumption and can be eaten on their own or added to soups and salads.

Tofu is made from bean curds pressed together in a process similar to cheesemaking. Tempeh is made by cooking and slightly fermenting mature soybeans prior to pressing them into a patty.

Tofu doesn’t have much taste, but easily absorbs the flavor of the ingredients it’s prepared with. Comparatively, tempeh has a characteristic nutty flavor.

Both tofu and tempeh can be used in a variety of recipes, ranging from burgers to soups and chilis.

All three contain iron, calcium and 10-19 grams of protein per 3.5 ounces (100 grams) (rx, rx, rx).

Edamame are also rich in folate, vitamin K and fiber. Tempeh contains a good amount of probiotics, B vitamins and minerals such as magnesium and phosphorus.

BOTTOM LINE:Tofu, tempeh and edamame all originate from soybeans, a complete source of protein. They also contain good amounts of several other nutrients and can be used in a variety of recipes.

3. Lentils

At 18 grams of protein per cooked cup (240 ml), lentils are a great source of protein (rx).

They can be used in a variety of dishes, ranging from fresh salads to hearty soups and spice-infused dahls.

Lentils also contain good amounts of slowly digested carbs, and a single cup (240 ml) provides approximately 50% of your recommended daily fiber intake.

Furthermore, the type of fiber found in lentils has been shown to feed the good bacteria in your colon, promoting a healthy gut. Lentils may also help reduce the risk of heart disease, diabetes, excess body weight and some types of cancer (rx).

In addition, lentils are rich in folate, manganese and iron. They also contain a good amount of antioxidants and other health-promoting plant compounds (rx).

BOTTOM LINE:Lentils are nutritional powerhouses. They are rich in protein and contain good amounts of other nutrients. They may also help reduce the risk of various diseases.

4. Chickpeas and Most Varieties of Beans

Kidney, black, pinto and most other varieties of beans contain high amounts of protein per serving.

Chickpeas, also known as garbanzo beans, are another legume with high protein content.

Both beans and chickpeas contain about 15 grams of protein per cooked cup (240 ml). They are also excellent sources of complex carbs, fiber, iron, folate, phosphorus, potassium, manganese, and several beneficial plant compounds (rx, rx, rx).

Moreover, several studies show that a diet rich in beans and other legumes can decrease cholesterol, help control blood sugar levels, lower blood pressure and even reduce belly fat (rx, rx, rx,rx).

Add beans to your diet by making a tasty bowl of homemade chili, or enjoy extra health benefits by sprinkling a dash of turmeric on roasted chickpeas (rx).

BOTTOM LINE:Beans are health-promoting, protein-packed legumes that contain a variety of vitamins, minerals and beneficial plant compounds.

5. Nutritional Yeast

Nutritional yeast is a deactivated strain of Saccharomyces cerevisiae yeast, sold commercially as a yellow powder or flakes.

It has a cheesy flavor, which makes it a popular ingredient in dishes like mashed potatoes and scrambled tofu.

Nutritional yeast can also be sprinkled on top of pasta dishes or even enjoyed as a savory topping on popcorn.

This complete source of plant protein provides the body with 14 grams of protein and 7 grams of fiber per ounce (28 grams) (rx).

Fortified nutritional yeast is also an excellent source of zinc, magnesium, copper, manganese and all the B vitamins, including B12 (rx).

However, fortification is not universal and unfortified nutritional yeast should not be relied on as a source of vitamin B12.

BOTTOM LINE:Nutritional yeast is a popular plant-based ingredient often used to give dishes a dairy-free cheese flavor. It is high in protein, fiber and is often fortified with various nutrients, including vitamin B12.

6. Spelt and Teff

Spelled and teff belong to a category known as ancient grains. Other ancient grains include einkorn, barley, sorghum, and farro.

Spelled is a type of wheat and contains gluten, whereas teff originates from an annual grass, which means it’s gluten-free.

Spelled and teff provide 10–11 grams of protein per cooked cup (240 ml), making them higher in protein than other ancient grains (rx, rx).

Both are excellent sources of various nutrients, including complex carbs, fiber, iron, magnesium, phosphorus, and manganese. They also contain good amounts of B vitamins, zinc, and selenium.

Spelled and teff are versatile alternatives to common grains, such as wheat and rice, and can be used in many recipes ranging from baked goods to polenta and risotto.

You can purchase spelled and teff online.

BOTTOM LINE:Spelt and teff are high-protein ancient grains. They’re a great source of various vitamins and minerals and an interesting alternative to more common grains.

7. Hempseed

Hempseed comes from the Cannabis sativa plant, which is notorious for belonging to the same family as the marijuana plant.

But hempseed contains only trace amounts of THC, the compound that produces the marijuana-like drug effects.

Although not as well-known as other seeds, hempseed contains 10 grams of complete, easily digestible protein per ounce (28 grams). That’s 50% more than chia seeds and flaxseeds (rx, rx).

Hempseed also contains a good amount of magnesium, iron, calcium, zinc and selenium. What’s more, it’s a good source of omega-3 and omega-6 fatty acids in the ratio considered optimal for human health (rx).

Interestingly, some studies indicate that the type of fats found in hempseed may help reduce inflammation, as well as diminish symptoms of PMS, menopause, and certain skin diseases (rx, rx, rx, rx, rx).

You can add hemp seed to your diet by sprinkling some in your smoothie or morning muesli. It can also be used in homemade salad dressings or protein bars.

BOTTOM LINE:Hempseed contains a good amount of complete, highly-digestible protein, as well as health-promoting essential fatty acids in a ratio optimal for human health

8. Green Peas

The little green peas often served as a side dish contain 9 grams of protein per cooked cup (240 ml), which is slightly more than a cup of milk (rx).

What’s more, a serving of green peas covers more than 25% of your daily fiber, vitamin A, C, K, thiamine, folate, and manganese requirements.

Green peas are also a good source of iron, magnesium, phosphorus, zinc, copper and several other B vitamins (rx).

You can use peas in recipes such as pea and basil stuffed ravioli, thai-inspired pea soup or pea and avocado guacamole.

BOTTOM LINE:Green peas are high in protein, vitamins and minerals and can be used as more than just a side dish.

9. Spirulina

This blue-green algae is definitely a nutritional powerhouse.

Two tablespoons (30 ml) provide you with 8 grams of complete protein, in addition to covering 22% of your daily requirements of iron and thiamin and 42% of your daily copper needs (rx).

Spirulina also contains decent amounts of magnesium, riboflavin, manganese, potassium and small amounts of most of the other nutrients your body needs, including essential fatty acids.

Phycocyanin, a natural pigment found in spirulina, appears to have powerful antioxidant, anti-inflammatory and anti-cancer properties (rx, rx, rx).

Furthermore, studies link consuming spirulina to health benefits ranging from a stronger immune system and reduced blood pressure to improved blood sugar and cholesterol levels (rx, rx, rx, rx).

BOTTOM LINE:Spirulina is a nutritious high-protein food with many beneficial health-enhancing properties.

10. Amaranth and Quinoa

Although often referred to as ancient or gluten-free grains, amaranth and quinoa don’t grow from grasses like other cereal grains do.

For this reason, they’re technically considered “pseudocereals.”

Nevertheless, they can be prepared or ground into flours similar to more commonly known grains.

Amaranth and quinoa provide 8–9 grams of protein per cooked cup (240 ml) and are complete sources of protein, which is rare among grains and pseudocereals (rx, rx).

Also, amaranth and quinoa are good sources of complex carbs, fiber, iron, manganese, phosphorus and magnesium (rx, rx).

BOTTOM LINE:Amaranth and quinoa are pseudocereals that provide you with a complete source of protein. They can be prepared and eaten similar to traditional grains such as wheat and rice.

11. Ezekiel Bread and Other Bread Made From Sprouted Grains

Ezekiel bread is made from organic, sprouted whole grains and legumes. These include wheat, millet, barley, and spelt, as well as soybeans and lentils.

Two slices of Ezekiel bread contain approximately 8 grams of protein, which is slightly more than the average bread (rx).

Sprouting grains and legumes increases the number of healthy nutrients they contain and reduces the number of anti-nutrients in them (rx, rx).

In addition, studies show that sprouting increases their amino acid content. Lysine is the limiting amino acid in many plants, and sprouting increases the lysine content. This helps boost the overall protein quality (rx).

Similarly, combining grains with legumes could further improve the bread’s amino acid profile (rx).

Sprouting also seems to increase the bread’s soluble fiber, folate, vitamin C, vitamin E and beta-carotene content. It may also slightly reduce the gluten content, which can enhance digestion in those sensitive to gluten (rx, rx).

BOTTOM LINE:Ezekiel and other breads made from sprouted grains have an enhanced protein and nutrient profile, compared to more traditional breads.

12. Soy Milk

Milk that’s made from soybeans and fortified with vitamins and minerals is a great alternative to cow’s milk.

Not only does it contain 7 grams of protein per cup (240 ml), but it’s also an excellent source of calcium, vitamin D and vitamin B12 (rx).

However, keep in mind that soy milk and soybeans do not naturally contain vitamin B12, so picking a fortified variety is recommended.

Soy milk is found in most supermarkets. It’s an incredibly versatile product that can be consumed on its own or in a variety of cooking and baking recipes.

It is a good idea to opt for unsweetened varieties to keep the amount of added sugars to a minimum.

BOTTOM LINE:Soy milk is a high-protein plant alternative to cow’s milk. It’s a versatile product that can be used in a variety of ways.

13. Oats and Oatmeal

Oats are an easy and delicious way to add protein to any diet.

Half a cup (120 ml) of dry oats provides you with approximately 6 grams of protein and 4 grams of fiber. This portion also contains good amounts of magnesium, zinc, phosphorus and folate (rx).

Although oats are not considered a complete protein, they do contain higher-quality protein than other commonly consumed grains like rice and wheat.

You can use oats in a variety of recipes ranging from oatmeal to veggie burgers. They can also be ground into flour and used for baking.

BOTTOM LINE:Oats are not only nutritious but also an easy and delicious way to incorporate plant protein into a vegan or vegetarian diet.

14. Wild Rice

Wild rice contains approximately 1.5 times as much protein as other long-grain rice varieties, including brown rice and basmati.

One cooked cup (240 ml) provides 7 grams of protein, in addition to a good amount of fiber, manganese, magnesium, copper, phosphorus and B vitamins (rx).

Unlike white rice, wild rice is not stripped of its bran. This is great from a nutritional perspective, as bran contains fiber and plenty of vitamins and minerals (rx).

However, this causes concerns about arsenic, which can accumulate in the bran of rice crops grown in polluted areas.

Arsenic is a toxic trace element that may give rise to various health problems, especially when ingested regularly for long periods of time (rx, rx,rx, rx).

Washing wild rice before cooking and using plenty of water to boil it may reduce the arsenic content by up to 57% (rx).

BOTTOM LINE:Wild rice is a tasty, nutrient-rich plant source of protein. Those relying on wild rice as a food staple should take precautions to reduce its arsenic content.

15. Chia Seeds

Chia seeds are derived from the Salvia hispanica plant, which is native to Mexico and Guatemala.

At 6 grams of protein and 13 grams of fiber per 1.25 ounces (35 grams), chia seeds definitely deserve their spot on this list (rx).

What’s more, these little seeds contain a good amount of iron, calcium, selenium and magnesium, as well as omega-3 fatty acids, antioxidants, and various other beneficial plant compounds (rx, rx).

They’re also incredibly versatile. Chia seeds have a bland taste and are able to absorb water, turning into a gel-like substance. This makes them an easy addition to a variety of recipes, ranging from smoothies to baked goods and chia puddings.

BOTTOM LINE:Chia seeds are a versatile source of plant protein. They also contain a variety of vitamins, minerals, antioxidants and other health-promoting compounds.

16. Nuts, Nut Butters, and Other Seeds

Nuts, seeds and their derived products are great sources of protein.

One ounce (28 grams) contains between 5–7 grams of protein, depending on the nut and seed variety (rx, rx, rx, rx, rx, rx).

Nuts and seeds are also great sources of fiber and healthy fats, in addition to iron, calcium, magnesium, selenium, phosphorus, vitamin E and certain B vitamins. They also contain antioxidants, among other beneficial plant compounds (rx).

When choosing which nuts and seeds to buy, keep in mind that blanching and roasting may damage the nutrients in nuts. So reach for raw, unblanched versions whenever possible (rx).

Also, try opting for natural nut butter to avoid the oil, sugar and excess salt often added to many household brand varieties.

BOTTOM LINE:Nuts, seeds and their butters are an easy way to add plant protein, vitamins and minerals to your diet. Opt to consume them raw, unblanched and with no other additives to maximize their nutrient content.

17. Protein-Rich Fruits and Vegetables

All fruits and vegetables contain protein, but the amounts are usually small.

However, some contain more than others.

Vegetables with the most protein include broccoli, spinach, asparagus, artichokes, potatoes, sweet potatoes and Brussels sprouts. They contain about 4–5 grams of protein per cooked cup (rx, rx, rx, rx, rx, rx, rx). Although technically a grain, sweet corn is a common food that contains about as much protein as these high-protein vegetables (rx).

Fresh fruits generally have a lower protein content than vegetables. Those containing the most include guava, cherimoyas, mulberries, blackberries, nectarines and bananas, which have about 2–4 grams of protein per cup (rx, rx, rx, ez, rx, rx).

BOTTOM LINE:Certain fruits and vegetables contain more protein than others. Include them in your meals to increase your daily protein intake.

Take-Home Message

Protein deficiencies among vegetarians and vegans are far from being the norm (rx). Nonetheless, some people may be interested in increasing their plant protein intake for a variety of reasons. This list can be used as a guide for anyone interested in incorporating more plant-based proteins into their diet.

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How much pantothenic acid should I take?

How much pantothenic acid should I take?/Pantothenic Acid is a water-soluble vitamin ubiquitously found in plants and animal tissues with antioxidant properties. Vitamin B5 is a component of coenzyme A (CoA) and a part of the vitamin B2 complex. Vitamin B5 is a growth factor and is essential for various metabolic functions, including the metabolism of carbohydrates, proteins, and fatty acids. This vitamin is also involved in the synthesis of cholesterol, lipids, neurotransmitters, steroid hormones, and hemoglobin.

Vitamin B or Pantothenic acid is a water-soluble vitamin. Pantothenic acid is an essential nutrient. Animals require pantothenic acid in order to synthesize coenzyme-A (CoA), as well as to synthesize and metabolize proteins, carbohydrates, and fats. The anion is called pantothenate. Pantothenic acid is the amide between pantoic acid and β-alanine. Its name derives from the Greek pantothen, meaning from everywhere, and small quantities of pantothenic acid are found in nearly every food, with high amounts in fortified whole-grain cereals, egg yolks, liver, and dried mushrooms. It is commonly found as its alcohol analog, the provitamin panthenol (pantothenol), and calcium pantothenate.

Deficiency Symptoms of Pantothenic Acid / Vitamin B5

Pantothenic acid deficiency has only been observed in individuals who were fed diets virtually devoid of pantothenic acid or who were given a pantothenic acid metabolic antagonist, omega-methyl pantothenic acid. The subjects exhibited various degrees of signs and symptoms, including irritability and restlessness; fatigue; apathy; malaise; sleep disturbances; gastrointestinal complaints such as nausea, vomiting, and abdominal cramps; neurobiological symptoms such as numbness, paresthesias, muscle cramps, and staggering gait; and hypoglycemia and increased sensitivity to insulin.

Symptoms of a vitamin B5 deficiency may include

Recommended Intakes of Vitamin B5

Intake recommendations for pantothenic acid and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and sex, include:

  • Recommended Dietary Allowance (RDA) – Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
  • Adequate Intake (AI) – Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
  • Estimated Average Requirement (EAR) – Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
  • Tolerable Upper Intake Level (UL) – Maximum daily intake unlikely to cause adverse health effects.

When the FNB evaluated the available data, it found the data insufficient to derive an EAR for pantothenic acid. Consequently, the FNB established AIs for all ages based on usual pantothenic acid intakes in healthy populations.

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Adequate Intakes (AIs) for Pantothenic Acid 
Age Male Female Pregnancy Lactation
Birth to 6 months 1.7 mg 1.7 mg
7–12 months 1.8 mg 1.8 mg
1–3 years 2 mg 2 mg
4–8 years 3 mg 3 mg
9–13 years 4 mg 4 mg
14–18 years 5 mg 5 mg 6 mg 7 mg
19+ years 5 mg 5 mg 6 mg 7 mg

Dietary Reference Intakes for Pantothenic Acid by Life Stage Group (mg/day)

Adequate Intake
Life Stage Group
0-6 mo 1.7
7-12 mo 1.8
1-3 yr 2
4-8 yr 3
9-13 yr 4
14-18 yr 5
19-30 yr 5
31-50 yr 5
51-70 yr 5
> 70 yr 5
Pregnancy
< or = 18 yr 6
19-50 yr 6
Lactation
< or = 18 yr 7
19-50 yr 7

 

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Food Source of Pantothenic Acid / Vitamin B5

Several food sources of pantothenic acid are listed bellow

 Selected Food Sources of Pantothenic Acid 
Food Milligrams
(mg) per
serving
Percent
DV*
Breakfast cereals, fortified with 100% of the DV 10 100
Beef liver, boiled, 3 ounces 8.3 83
Shitake mushrooms, cooked, ½ cup pieces 2.6 26
Sunflower seeds, ¼ cup 2.4 24
Chicken, breast meat, skinless, roasted, 3 ounces 1.3 13
Tuna, fresh, bluefin, cooked, 3 ounces 1.2 12
Avocados, raw, ½ avocado 1.0 10
Milk, 2% milkfat, 1 cup 0.9 9
Mushrooms, white, stir-fried, ½ cup sliced 0.8 8
Potatoes, russet, flesh, and skin, baked, 1 medium 0.7 7
Egg, hard-boiled, 1 large 0.7 7
Greek yogurt, vanilla, nonfat, 5.3-ounce container 0.6 6
Ground beef, 85% lean meat, broiled, 3 ounces 0.6 6
Peanuts, roasted in oil, ¼ cup 0.5 5
Broccoli, boiled, ½ cup 0.5 5
Whole-wheat pita, 1 large 0.5 5
Chickpeas, canned, ½ cup 0.4 4
Rice, brown, medium-grain, cooked, ½ cup 0.4 4
Oats, regular and quick, cooked with water, ½ cup 0.4 4
Cheese, cheddar, 1.5 ounces 0.2 2
Carrots, chopped, raw, ½ cup 0.2 2
Cabbage, boiled, ½ cup 0.1 1
Clementine, raw, 1 clementine 0.1 1
Tomatoes, raw, chopped or sliced, ½ cup 0.1 1
Cherry tomatoes, raw, ½ cup 0 0
Apple, raw, slices, ½ cup 0 0

*DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration (FDA) to help consumers compare the nutrient contents of products within the context of a total diet. The DV for the values in Table 2 is 10 mg for adults and children age 4 years and older. This value, however, decreases to 5 mg when the updated Nutrition and Supplement Facts labels are implemented. The updated labels must appear on food products and dietary supplements beginning in January 2020, but they can be used now. The FDA does not require food labels to list pantothenic acid content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.

The U.S. Department of Agriculture’s (USDA’s) National Nutrient Database for Standard Reference website lists the nutrient content of many foods and provides a comprehensive list of foods containing pantothenic acid arranged by pantothenic acid content and by food name.

Health Benefit of Pantothenic Acid / Vitamin B5

  • Pantothenic acid – has been used for a wide range of disorders such as acne, alopecia, allergies, burning feet, asthma, grey hair, dandruff, cholesterol-lowering, improving exercise performance, depression, osteoarthritis, rheumatoid arthritis, multiple sclerosis, stress, shingles, aging and Parkinson’s disease. It has been investigated in clinical trials for arthritis, cholesterol-lowering and exercise performance.[Mason P; Dietary Supplements,
  • The topical application of pantothenate –  is widely used in clinical practice for wound healing.
  • Pantothenic acid deficiency –  Taking pantothenic acid by mouth prevents and treats pantothenic acid deficiency.
  • Skin reactions from radiation therapy – Applying dexpanthenol, a chemical similar to pantothenic acid, to areas of irritated skin does not seem to help treat skin reactions from radiation therapy.
  • Some research suggests that taking pantothenic acid in combination with pantethine and thiamine does not improve muscular strength or endurance in well-trained athletes.
  • There is conflicting evidence regarding the usefulness of pantothenic acid in combination with large doses of other vitamins for the treatment of ADHD.
  • Early research suggests that taking dexpanthenol, a chemical similar to pantothenic acid, by mouth daily or receiving dexpanthenol shots can help treat constipation.
  • Early research suggests that using specific eye drops (Siccaprotect) containing dexpanthenol, a chemical similar to pantothenic acid, does not improve most symptoms of dry eyes.
  • Some evidence suggests that applying gel or drops containing dexpanthenol, a chemical similar to pantothenic acid, reduces some symptoms of eye trauma. However, not all research is consistent.
  • Early research suggests that pantothenic acid (given as calcium pantothenate) does not reduce symptoms of osteoarthritis.
  • There is inconsistent evidence on the potential benefits of taking pantothenic acid after surgery. Taking pantothenic acid or dexpanthenol, a chemical similar to pantothenic acid, does not seem to improve bowel function after stomach surgery. However, taking dexpanthenol by mouth might reduce other symptoms after surgery, such as sore throat.
  • Developing research suggests that pantothenic acid (given as calcium pantothenate) does not reduce the symptoms of arthritis in people with rheumatoid arthritis.
  • Early research suggests that using a specific spray (Nasicur) that contains dexpanthenol, a chemical similar to pantothenic acid, helps relieve nasal dryness.
  • Early research suggests that using a nasal spray containing dexpanthenol, a chemical similar to pantothenic acid, after sinus surgery reduces discharge from the nose, but not other symptoms.
  • Research on the effects of pantothenic acid for preventing skin irritations is not consistent. Some early research suggests that a specific product (Bepanthol Handbalsam) containing dexpanthenol, a chemical similar to pantothenic acid, does not prevent skin irritation when applied to the skin. However, other research suggests that dexpanthenol ointment can prevent skin irritation.
  • Early research suggests that using a specific ointment (Hepathrombin-50,000-Salbe Adenylchemie) containing dexpanthenol, a chemical similar to pantothenic acid, as well as heparin and allantoin reduces swelling related to ankle sprains.
  • Alcoholism.
  • Allergies.
  • Hair loss.
  • Asthma.
  • Heart problems.
  • Carpal tunnel syndrome.
  • Lung disorders.
  • Colitis.
  • Eye infections (conjunctivitis).
  • Convulsions.
  • Kidney disorders.
  • Dandruff.
  • Depression.
  • Diabetic problems.
  • Enhancing immune function.
  • Headache.
  • Hyperactivity.
  • Low blood pressure.
  • Inability to sleep (insomnia).
  • Irritability.
  • Multiple sclerosis.
  • Muscular dystrophy.
  • Muscle cramps.

References

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