Vitamin B6

by MedlinePlus

In 1936, a scientist named Gyorgy distinguished the water-soluble factor from vitamin B2 and named it vitamin B6. The chemical structure of vitamin B6 was elucidated in 1939.

Vitamin B6 (pyridoxine) is required for the synthesis of the neurotransmitters serotonin and norepinephrine, and for myelin formation.

Pyridoxine deficiency in adults principally affects the peripheral nerves, skin, mucous membranes, and the hematopoietic system. In children, the central nervous system (CNS) is also affected. Deficiency can occur in people with uremia, alcoholism, cirrhosis, hyperthyroidism, malabsorption syndromes, congestive heart failure (CHF), and in those taking certain medications.

Mild deficiency of vitamin B6 is common. Major sources of vitamin B6 include: cereal grains, legumes, vegetables (carrots, spinach, peas), potatoes, milk, cheese, eggs, fish, liver, meat, and flour.

Pyridoxine is frequently used in combination with other B vitamins in vitamin B complex formulations. Vitamin B complex products may also include vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin/niacinamide), vitamin B5 (pantothenic acid), vitamin B12 (cyanocobalamin), folic acid, biotin, para-aminobenzoic acid (PABA), choline bitartrate, and inositol.

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidence

Hereditary sideroblastic anemia

Pyridoxine supplements are effective for treating hereditary sideroblastic anemia under the supervision of a qualified healthcare provider.

Preventing adverse effects in people taking cycloserine (Seromycin®)

Cycloserine is a prescription antibiotic that may cause anemia, peripheral neuritis or seizures by acting as a pyridoxine antagonist or increasing excretion of pyridoxine. Requirements for pyridoxine may be increased in patients receiving cycloserine. Pyridoxine 100-300mg daily taken in divided doses may be recommended by a healthcare provider to prevent these adverse effects.

Pyridoxine deficiency/ neuritis

Pyridoxine supplements are effective for preventing and treating pyridoxine deficiency and neuritis due to inadequate dietary intake, certain disease states, or deficiency induced by drugs such as isoniazid (INH) or penicillamine. Dietary supplements should be taken under the guidance of a qualified healthcare provider.

Pyridoxine-dependent seizures in newborns

Pyridoxine-dependent seizures in newborns can result from use of high-dose pyridoxine in pregnant mothers or from genetic (autosomal recessive) pyridoxine dependency. Refractory seizures in newborns that are caused by pyridoxine dependence may be controlled quickly with intravenous administration of pyridoxine by a qualified healthcare provider.

Akathisia (movement disorder)

Some prescription drugs called neuroleptics which are used in psychiatric conditions may cause movement disorders as an unwanted side effect. Vitamin B6 has been studied for treatment of acute neuroleptic-induced akathisia (NIA) in schizophrenic and schizoaffective disorder patients. Preliminary results indicate that high doses of vitamin B6 may be useful additions to the available treatments for NIA, perhaps due to its combined effects on various neurotransmitter systems. Further research is needed to confirm these results.

Angioplasty

There are conflicting findings about the potential benefit or harm of taking folic acid plus vitamin B6 and vitamin B12 following angioplasty. Further research is needed before a recommendation can be made.

Asthma

Preliminary research suggests that children with severe asthma might have inadequate pyridoxine status. Theophylline, a prescription drug used to help manage asthma, seems to lower pyridoxine levels. Studies of pyridoxine supplementation in asthma patients taking theophylline yield conflicting results. Further research is needed before a conclusion can be drawn.

Attention deficit-hyperactivity disorder (ADHD)

Some research suggests that pyridoxine supplementation alone or in combination with high doses of other B vitamins might help ADHD. Other studies show no benefit. Further research is needed before a conclusion can be drawn.

Birth outcomes

Studies of birth outcomes with vitamin B6 supplementation during pregnancy yield mixed results. Further prospective, multicenter, randomized trials might be helpful in this area.

Cardiovascular disease/ hyperhomocysteinemia

High homocysteine levels in the blood (hyperhomocysteinemia) are a risk factor for cardiovascular disease, blood clotting abnormalities, myocardial infarction, and ischemic stroke. Taking pyridoxine supplements alone or in combination with folic acid has been shown to be effective for lowering homocysteine levels. However, it is not clear if lowering homocysteine levels results in reduced cardiovascular morbidity and mortality. Until definitive data is available, the current recommendation is screening of 40-year-old men and 50-year-old women for hyperhomocysteinemia.Decreased pyridoxine concentrations are also associated with increased plasma levels of C-reactive protein (CRP). CRP is an indicator of inflammation that is associated with increased cardiovascular morbidity in epidemiologic studies.Pyridoxine may reduce homocysteine levels in patients with end-stage renal disease (ESRD), renal transplant patients, and patients who receive general anesthesia with nitrous oxide. High doses of B vitamins may be required to correct hyperhomocysteinemia in dialysis patients. Investigation of more renal transplant recipients undergoing longer treatment with Vitamin B6 is needed as study results conflict.

Carpal tunnel syndrome

Preliminary data suggests that large doses of vitamin B6 may be helpful for carpal tunnel syndrome. Well designed clinical trials are needed before a firm conclusion can be drawn.

Depression

Preliminary evidence suggests that because pyridoxine increases serotonin and GABA levels in the blood, it may benefit people in dysphoric mental states.One small randomized, placebo-controlled double-blind trial suggests that vitamins B1, B2, and B6 may add to the effects of tricyclic antidepressants in the treatment of affective and/or cognitive disturbances in geriatric depression. Well designed clinical trials are needed to confirm potential benefit.

Hyperkinetic cerebral dysfunction syndrome

There is preliminary evidence that pyridoxine supplementation might benefit hyperkinetic children who have low levels of blood serotonin. Further research is needed to confirm these results.

Immune system function

Vitamin B6 is important for immune system function in older individuals. One study found that the amount of vitamin B6 required to reverse immune system impairments in elderly people was more than the current recommended dietary allowance (RDA). Well designed clinical trials on vitamin B6 supplementation for this indication are needed before a recommendation can be made.

Kidney stones (nephrolithiasis)

Pyridoxine alone, or taken with magnesium, may decrease urinary oxalate levels which can contribute to a certain type of kidney stones. Higher pyridoxine intake has been associated with decreased risk of kidney stone formation in women but not in men with no history of stone formation. Benefit has not been proven in other types of kidney stones such as those associated with high urinary calcium, phosphorus, and creatinine. Further data is needed before a firm conclusion can be drawn.

Lactation suppression

Study results of pyridoxine used to suppress lactation yield mixed results. Well designed clinical trials are needed before a firm conclusion can be drawn.

Lung cancer

Epidemiological research suggests that male smokers with higher serum levels of pyridoxine may have a lower risk of lung cancer. Well designed clinical trails of pyridoxine supplementation are needed to confirm these results and supplementation is not standard therapy at this time.

Pregnancy-induced nausea and vomiting

Studies of the use of pyridoxine alone or in combination with other antinausea treatments in pregnant women yield conflicting results. PremesisRx® (75mg sustained-release pyridoxine, 12mcg vitamin B12 (cyanocobalamin), 1mg folic acid, and 200mg calcium) has been used daily as an FDA-approved prescription supplement for nausea during pregnancy. Further research is needed before a recommendation can be made.Pyridoxine and the sedative antihistamine doxylamine were ingredients in Bendectin, a widely-prescribed antinausea product for use in pregnancy. The product was removed from the US market in 1983 due to litigation costs. However, animal studies of pyridoxine and Bendectin do not show fetal harm from Bendectin ingredients. Following removal of Bendectin from the market, there was no reduction in birth defects, but hospitalization rates for pregnancy-related nausea and vomiting doubled. Diclectin is a similar product sold in Canada.

Premenstrual syndrome (PMS)

There is some evidence that taking pyridoxine orally may improve symptoms of PMS such as breast pain or tenderness (mastalgia) and PMS-related depression in some patients. Pyridoxine 50mg per day plus magnesium oxide 200mg per day seemed to relieve PMS-related anxiety in one study. Further research is needed before a recommendation can be made.

Preventing vitamin B6 deficiency associated with taking birth control pills

The need for vitamin B6 supplementation in women taking birth control pills has not been proven although some studies show decreased pyridoxine levels in these women. Supplementation of B6 should be approached cautiously since the long-term effect of such therapy is uncertain.

Tardive dyskinesia

Pyridoxine has some antioxidant effects which theoretically may benefit patients with tardive dyskinesia. In one study, supplementation with pyridoxine 400mg per day seemed to improve Parkinsonian, dystonic, and dyskinetic symptoms in patients taking neuroleptic drugs for schizophrenia. Further research is needed before a recommendation can be made.

Autism

Studies of B6 supplementation alone or in combination with magnesium have not been shown to benefit autism. Autism should be treated by a qualified healthcare provider.

Stroke reoccurrence

Pyridoxine alone or in combination with B12 and folic acid orally does not seem to be useful for preventing stroke recurrence.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Acne, alcohol intoxication, allergies, appetite stimulation, arthritis, cancer prevention, chorea, conjunctivitis, cystitis, diabetic neuropathy, diuresis, dizziness, Down's syndrome, high cholesterol, improving dream recall, infertility, menopausal symptoms, migraine headaches, motion sickness, muscle cramps, mushroom poisoning, night leg cramps, psychosis, radiation sickness, sickle cell anemia, skin conditions.

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