Herbs & Supplements:
Vitamin B6

Supplement Forms / Alternate Names
  • Pyridoxine, Pyridoxine Hydrochloride, Pyridoxal-5-Phosphate
Principal Proposed Uses
  • Heart Disease Prevention, Morning Sickness in Pregnancy, PMS
Other Proposed Uses
  • MSG Sensitivity, Carpal Tunnel Syndrome, Diabetic Neuropathy, Kidney Stones, Depression, Asthma, HIV Support, Tardive Dyskinesia, Photosensitivity, Vertigo, Autism (B6 Combined with Magnesium), Seborrheic Dermatitis, Parkinson's Disease

Vitamin B₆ plays a major role in making proteins, hormones, and neurotransmitters (chemicals that carry signals between nerve cells). Because mild deficiency of vitamin B₆ is common, this is one vitamin that is probably worth taking as insurance.

There's good evidence that adequate intake of vitamin B₆ can help prevent heart disease and reduce the nausea of morning sickness. This vitamin is also widely recommended for premenstrual syndrome (PMS) and asthma, but there is little evidence that it is effective for either use. When combined with magnesium, vitamin B₆ may be helpful for autism.

Requirements/Sources

Vitamin B₆ requirements increase with age. The official U.S. and Canadian recommendations for daily intake are as follows:

• Infants 0–6 months, 0.1 mg
  7–12 months, 0.3 mg
• Children 1–3 years, 0.5 mg
  4–8 years, 0.6 mg
  9–13 years, 1.0 mg
• Males 14–50 years, 1.3 mg
  51 years and older, 1.7 mg
• Females 14–18 years, 1.2 mg
  19–50 years, 1.3 mg
  51 years and older, 1.5 mg
• Pregnant women, 1.9 mg
• Nursing women, 2.0 mg

Severe deficiencies of vitamin B₆ are rare, but mild deficiencies are extremely common. In a survey of 11,658 adults, 71% of men and 90% of women were found to have diets deficient in B₆.¹ Vitamin B₆ is the most commonly deficient water-soluble vitamin in the elderly,² and children, too, don't get enough.³ In addition, evidence has been presented that current recommended daily intakes should be increased.⁴

B₆ deficiency might be worsened by use of hydralazine (for high blood pressure),⁵ penicillamine (used for rheumatoid arthritis and certain rare diseases),⁶ theophylline (an older drug for asthma),^7–11 MAO inhibitors,¹² and the antituberculosis drug isoniazid (INH),^13–16 all of which are thought to interfere with B₆ to some degree. Good sources of B₆ include nutritional (torula) yeast, brewer's yeast, sunflower seeds, wheat germ, soybeans, walnuts, lentils, lima beans, buckwheat flour, bananas, and avocados.

Therapeutic Dosages

When used therapeutically, B₆ is commonly recommended at a daily dose of 10 to 300 mg, much higher than the basic nutritional requirement. However, it's probably not wise to take more than the safe upper intake levels (see Safety Issues).

Since the B vitamins tend to work together, many nutritional experts recommend taking B₆ with other B vitamins, perhaps in the form of a B-complex supplement.

Therapeutic Uses

There is meaningful evidence that an intake of vitamin B₆ somewhat above the recommended daily intake levels (4.6 mg or more daily) can significantly reduce the risk of heart disease.¹⁷

A large double-blind study suggests that a higher dose (30 mg daily) of vitamin B₆ can reduce the nausea of morning sickness.¹⁸

Other common uses of B₆ are not very well established. For example, vitamin B₆ is widely recommended by conventional physicians as a treatment for carpal tunnel syndrome.However, there is little to no evidence that it actually works.^19–22 Similarly, although B₆ is frequently suggested as a treatment for PMS (premenstrual syndrome), there is some fairly good evidence that it doesn't work for this purpose.²³

Some natural medicine authorities state that vitamin B₆ is a useful treatment for diabetic neuropathy. This idea is based on the fact that B₆ deficiency can cause neuropathy, and people with diabetes may be low in B₆. However, there is clinical evidence that B₆ supplements do not help diabetic neuropathy.^24,25,26

Vitamin B₆ might help prevent calcium oxalate,²⁷ and a small uncontrolled study found that supplementation decreased oxalate excretion in people with a history of kidney stones,^28,29 although not all studies agree.³⁰

A double-blind trial conducted in the 1970s found some evidence that vitamin B6 might be helpful for childhood asthma,³² but a more recent and better-designed trial in adults failed to find any evidence that use of vitamin B6 improved symptoms.³³

Very weak evidence suggests that B₆ may be helpful for depression,³¹ allergy to monosodium glutamate (MSG, a highly allergenic food additive used to enhance flavor), diabetes caused by pregnancy (gestational diabetes),³⁴ HIV infection,^35,36tardive dyskinesia,^37,38,39,82photosensitivity,⁴⁰ and vertigo.⁴¹ Vitamin B₆ also might help reduce nervous system side effects such as hand tremors associated with the use of the asthma drug theophylline.^42,43,44

An interesting series of studies suggests (but certainly doesn't prove) that the combination of vitamin B₆ and magnesium can be helpful in autism.^45–55 Finally, one preliminary study suggests topical vitamin B₆ may help with the skin disease seborrheic dermatitis.⁵⁶

Vitamin B₆ is sometimes suggested as a treatment for Parkinson's disease; however, no real evidence as yet supports this use.

In analogy to its proposed use in pregnancy and PMS, vitamin B6 has been tried as a treatment to reduce side effects of oral contraceptives. However, a 30-day double-blind trial of 124 women failed to find any benefit with 150 mg of vitamin B6 daily.⁸⁴

A small 30-day double-blind trial failed to find vitamin B6 at a dose of 50 mg daily helpful for eczema ⁸⁵

What Is the Scientific Evidence for Vitamin B6?

Prevention of Atherosclerosis/Heart Disease

According to data gathered in the Nurses' Health Study, one of the largest long-term medical studies ever performed, vitamin B₆ supplements can significantly reduce a woman's risk of developing heart disease.⁵⁷ A total of 80,000 women with no history of heart disease were studied for possible links between vitamin B₆, folate, and the development of heart disease. The results showed that increased intake of B₆ could significantly reduce the risk of heart disease. 

Vitamin B₆ (in combination with folate and vitamin B₁₂) reduces blood levels of homocysteine, a chemical that has been linked to hardening of the arteries and heart disease. At first, it was assumed that the benefits of vitamin B₆ were all due to reducing homocysteine. However, a subsequent study found no association between high homocysteine levels and the risk of heart disease.⁵⁸ Instead, researchers found a connection between heart disease and low levels of vitamin B₆. People with the highest vitamin B₆ levels were 28% less likely to develop heart disease than those with the lowest B₆ levels. This study has led to the hypothesis that it is vitamin B₆ itself that reduces heart disease risk, and the reduction of homocysteine seen at the same time is simply incidental. However, the matter remains controversial. One thing we do know is that even in the presence of adequate folate and vitamin B₁₂, B₆ supplementation reduces homocysteine levels.⁵⁹

Vitamin B₆ may help the heart in several ways. Preliminary studies suggest that it can reduce the tendency of platelets in the blood to form clots,⁶⁰ and also lower blood pressure to some extent.⁶¹

Morning Sickness (Nausea and Vomiting in Pregnancy)

Vitamin B₆ supplements have been used for years by conventional physicians as a treatment for morning sickness. In 1995, a large double-blind study validated this use.⁶² A total of 342 pregnant women were given placebo or 30 mg of vitamin B₆ daily. Subjects then graded their symptoms by noting the severity of their nausea and recording the number of vomiting episodes. The women in the B₆ group experienced significantly less nausea than those in the placebo group, suggesting that regular use of B₆ can be helpful for morning sickness. However, vomiting episodes were not significantly reduced.

Premenstrual Syndrome (PMS)

A recent, properly designed, double-blind study of 120 women found no benefit of vitamin B₆ for PMS.⁶³ In this study, three prescription drugs were compared against vitamin B₆ (pyridoxine, at 300 mg daily) and placebo. All study participants received 3 months of treatment and 3 months of placebo. Vitamin B₆ proved to be no better than placebo.

Approximately a dozen other double-blind studies have investigated the effectiveness of vitamin B₆ for PMS, but none were well designed, and overall the evidence for any benefit is weak at most.^64,65 Some books on natural medicine report that the negative results in some of these studies were due to insufficient B₆ dosage, but in reality there was no clear link between dosage and effectiveness.

However, preliminary evidence suggests that the combination of B₆ and magnesium might be more effective than either treatment alone.⁶⁶

Autism

Six double-blind placebo-controlled trials enrolling a total of about 150 children have evaluated the effects of vitamin B₆ and magnesium combination therapy for autism.^67–72 All of these studies found a significant improvement in autistic behaviors. However, the study design used in many of these trials was rather complicated and difficult to evaluate. For example, the largest trial (actually, a series of four closely intertwined trials) involved multiple groups of participants taking different treatments with inadequate time in between for the vitamins and minerals to wash out.⁷³ These studies were marked by other flaws as well; in addition, they were all performed by one research group.

For these reasons, until better-designed trials reported by independent laboratories are published, this therapy cannot be considered proven.

Asthma

A double-blind study of 76 children with asthma found significant benefit from vitamin B₆ after the second month of usage.⁷⁴ Children in the vitamin B₆ group were able to reduce their doses of asthma medication (bronchodilators and steroids). However, a recent double-blind study of 31 adults who used either inhaled or oral steroids did not show any benefit.⁷⁵ The dosages of B₆ used in these studies were quite high, in the range of 200 to 300 mg daily. Because of the risk of nerve injury, it is not advisable to take this much B₆ without medical supervision (see Safety Issues).

Safety Issues

The safe upper levels for daily intake of vitamin B₆ are as follows:⁸³

• Children 1–3 years, 30 mg
  4–8 years, 40 mg
• Males and females 9–13 years, 60 mg
  14–18 years, 80 mg
  19 years and older, 100 mg
• Pregnant or nursing women, 100 mg (80 mg if 18 years old or younger)

At higher dosages (especially above 2 g daily) there is a very real risk of nerve damage. Nerve-related symptoms have even been reported at doses as low as 200 mg.⁷⁶ (This is a bit ironic, given that B₆ deficiency also causes nerve problems.) In some cases, very high doses of vitamin B₆ can cause or worsen acne symptoms.^77,78

In addition, doses of vitamin B₆ over 5 mg may interfere with the effects of the drug levodopa when it is taken alone.^79,80,81 However, levodopa/carbidopa combinations are immune to this effect.

Maximum safe dosages for individuals with severe liver or kidney disease have not been established.

Interactions You Should Know About

If you are taking

• Isoniazid (INH),penicillamine, hydralazine,theophylline, or MAO inhibitors: You may need extra vitamin B₆, but take only nutritional doses. Higher doses of B₆ might interfere with the action of the drug.
• Levodopa (for Parkinson's disease): Do not take more than 5 mg of vitamin B₆ daily except on medical advice.

Last reviewed April 2002 by Medical Review Board

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