Vitamin B6; Deficiency Symptoms, Food Source, Health Benefit

Vitamin B₆ refers to a group of chemically similar compounds which can be interconverted in biological systems. Vitamin B₆ is part of the vitamin B group of essential nutrients. Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in some 100 enzyme reactions in amino acid, glucose, and lipid metabolize vitamin B6 in coenzyme forms performs a wide variety of functions in the body and is extremely versatile, with involvement in more than 100 enzyme reactions, mostly concerned with protein metabolism. Both PLP and PMP are involved in amino acid metabolism, and PLP is also involved in the metabolism of one-carbon units, carbohydrates, and lipids.

[stextbox id=’alert’]Vitamin B6 also plays a role in cognitive development through the biosynthesis of neurotransmitters and in maintaining normal levels of homocysteine, an amino acid in the blood. Vitamin B6 is involved in gluconeogenesis and glycogenolysis, immune function (for example, it promotes lymphocyte and interleukin-2 production), and hemoglobin formation. The human body absorbs vitamin B6 in the jejunum. Phosphorylated forms of the vitamin are dephosphorylated, and the pool of free vitamin B6 is absorbed by passive diffusion.[/stextbox]

Deficiency Symptoms of Vitamin B6

• fatigue
• depression
• irritability
• insomnia
• stomach pains
• tiredness
• apathy
• depression
• sleep disorders
• nausea -vomiting
• numbness
• muscle cramps
• hypoglycemia
• burning feet
• upper respiratory infections
• vomiting
• burning feet
• upper respiratory infections
• muscle cramps
• seborrhoeic dermatitis-like eruption
• atrophic glossitis with ulceration
• angular cheilitis,
• conjunctivitis
• intertrigo,
• neurologic
• symptoms of somnolence,
• confusion
• neuropathy (due to impaired sphingosine synthesis)
• sideroblastic anemia (due to impaired heme synthesis)
• metabolic disease associated with insufficient activity of the coenzyme PLP
• The most prominent of the lesions is due to impaired tryptophan–niacinconversion.
• This can be detected based on urinary excretion of xanthurenic acid after an oral tryptophan load.
• Vitamin B₆ deficiency can also result in impaired transsulfuration of methionine to cysteine.
• The PLP-dependent transaminases and glycogen phosphorylase provide the vitamin with its role in gluconeogenesis, so deprivation of vitamin B₆ results in impaired glucose tolerance.

Recommended Intakes of Vitamin B6

Intake recommendations for vitamin B6 and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the FNB . 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 gender, 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.

Table 1 lists the current RDAs for vitamin B6 . For infants from birth to 12 months, the FNB established an AI for vitamin B6 that is equivalent to the mean intake of vitamin B6 in healthy, breastfed infants.

* Adequate Intake (AI)

Food Source of Vitamin B6

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 vitamin B6 is 2 mg for adults and children age 4 and older. However, the FDA does not require food labels to list vitamin B6 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) Nutrient Database lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin B6 arranged by nutrient content and by food name.

*Breast milk, formula, and food should be the only sources of vitamin B6 for infants.

Health Benefit of Vitamin B6

• Anemia (sideroblastic anemia) – Taking pyridoxine by mouth is effective for treating an inherited type of anemia called sideroblastic anemia.
• Certain seizures in infants (pyridoxine-dependent seizures) – Administering pyridoxine intravenously (by IV) controls seizures in infants that are caused by pyridoxine dependence.
• Pyridoxine deficiency –  Taking pyridoxine by mouth is effective for preventing and treating pyridoxine deficiency.
• High homocysteine blood levels – Taking pyridoxine by mouth alone or together with folic acid is effective for treating high homocysteine levels in the blood.
• Macular degeneration –  Some research shows that taking pyridoxine with other vitamins including folic acid and vitamin B12 might help prevent the loss of vision caused by the eye disease called age-related macular degeneration.
• Behavior disorder in children caused by low serotonin levels (hyperkinetic cerebral dysfunction syndrome) – Early research shows that taking pyridoxine by mouth might have a beneficial effect on children with a behavior disorder caused by low serotonin levels.
• High blood pressure –  Early research suggests that taking pyridoxine can lower blood pressure in people with high blood pressure
• Kidney stones – There is some evidence that taking pyridoxine alone or combined with magnesium can decrease the risk of kidney stones in people with a hereditary disorder that increases their risk of forming kidney stones (type I primary hyperoxaluria). However, it does not appear to help people with other kinds of kidney stones.
• Lung cancer –  Taking pyridoxine by mouth seems to decrease the risk of lung cancer in individuals who smoke.
• Upset stomach and vomiting in pregnancy –  Some research suggests pyridoxine does not improve symptoms of mild to moderate nausea as much as severe nausea. The American College of Obstetrics and Gynecology considers pyridoxine a first-line treatment for nausea and vomiting caused by pregnancy. Pyridoxine plus the medication doxylamine is recommended for women who do not get better when treated with just pyridoxine.
• Premenstrual syndrome (PMS) – There is some evidence that taking pyridoxine by mouth can improve PMS symptoms including breast pain. The lowest effective dose should be used. Higher doses will increase the chance of side effects and are not likely to increase the beneficial effects.
• Movement disorders (tardive dyskinesia) –Taking pyridoxine seems to improve movement disorders in people taking drugs for mental disorders.
• Alzheimer’s disease – Some evidence suggests that taking pyridoxine supplements does not reduce the risk of Alzheimer’s disease in older people.
• Autism –  Taking pyridoxine with magnesium daily does not seem to improve autistic behavior in children.
• Carpal tunnel syndrome –  Although some early research suggests that pyridoxine might relieve certain symptoms of carpal tunnel syndrome, most research suggests that this supplement does not benefit people with this condition.
• Mental function  – Taking pyridoxine daily together with folic acid and vitamin B12 does not seem to improve mental function in older people.
• Stroke –  Taking pyridoxine by mouth does not seem to prevent the occurrence of another stoke in people with a history of stroke.
• Preventing re-blockage of blood vessels after angioplasty – Evidence on the benefits of pyridoxine for preventing the re-blockage of blood vessels after angioplasty is inconsistent. Some evidence suggests that taking folic acid, vitamin B12 and pyridoxine might be beneficial. However, other research finds no benefit.
• Asthma. The effectiveness of pyridoxine supplementation in children with asthma is unclear.
• Itchy and inflamed skin (atopic dermatitis (eczema)) – Early research suggests that taking pyridoxine daily for 4 weeks does not reduce eczema symptoms in children.
• Attention deficit-hyperactivity disorder (ADHD) – Early research suggests that taking pyridoxine by mouth, with or without high doses of B vitamins, might help ADHD. However, research using high doses of both pyridoxine and vitamins seems to have no effect on ADHD symptoms.
• Depression – Early research suggests that taking pyridoxine might reduce depression symptoms in postmenopausal women but not in the general population.
• Painful periods (dysmenorrhea) – Early research suggests that taking pyridoxine daily might reduce painful periods.
• Nerve problems caused by diabetes – Evidence on the effects of pyridoxine in people with nerve problems caused by diabetes is inconsistent. Some research shows that taking pyridoxine with thiamine daily reduces the severity of symptoms, while other research shows no benefit.
• High blood sugar during pregnancy (gestational diabetes) – Some early research suggests that taking pyridoxine daily for 2 weeks may lower sugar levels in women with high blood sugar during pregnancy. However other early research shows no benefit of pyridoxine on this condition.
• Nerve damage caused by tuberculosis medication – Early research suggests that taking pyridoxine daily might reduce nerve damage caused by a drug taken for tuberculosis.
• Stopping breast milk production – Early research suggests that taking pyridoxine daily for 6-7 days does not stop breast milk production.
• Complications in pregnancy – Taking pyridoxine during pregnancy does not seem to reduce the risk of eclampsia, pre-eclampsia, or preterm birth, but may reduce the risk of tooth decay.
• Seizures caused by a high fever (seizures) – Early research suggests that taking pyridoxine daily for 12 months does not reduce the recurrence of seizures caused by a high fever.
• Nerve damage caused by chemotherapy – Early research suggests that pyridoxine might help reverse nerve damage caused by the chemotherapy drug vincristine.
• Boosting the immune system.
• Muscle cramps.
• Eye problems.
• Kidney problems.
• Night leg cramps.
• Arthritis.
• Allergies.
• Lyme disease.

References

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