Vitamin B 6 plays a major role in making proteins, hormones, and neurotransmitters (chemicals that carry signals between nerve cells). Because mild deficiency of vitamin B 6 is common, this is one vitamin that is probably worth taking as insurance.
However, there is little evidence that taking vitamin B 6 above nutritional needs offers benefits in the treatment of any particular illnesses, except, possibly, nausea of pregnancy (morning sickness).
Vitamin B 6 requirements increase with age. The official US and Canadian recommendations for daily intake are as follows:
The National Institutes of Health's Office of Dietary Supplements offers this list of foods that are high in vitamin B 6:77
Vitamin B 6 Deficiency TOP
Severe deficiencies of vitamin B 6 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 B 6.1 Vitamin B 6 is the most commonly deficient water-soluble vitamin in the elderly,2 and children, too, often don't get enough.3 In addition, evidence has been presented that current recommended daily intakes should be increased.4
B 6 deficiency might be worsened by use of hydralazine (for high blood pressure),5penicillamine (used for rheumatoid arthritis and certain rare diseases),6theophylline (an older drug for asthma),7-11MAO inhibitors,12 and the antituberculosis drug isoniazid (INH),13-16 all of which are thought to interfere with B 6 to some degree. Good sources of B 6 include nutritional (torula) yeast, brewer's yeast, sunflower seeds, wheat germ, soybeans, walnuts, lentils, lima beans, buckwheat flour, bananas, and avocados.
Therapeutic Dosages TOP
One study found that 30 mg of vitamin B 6 daily was effective for symptoms of morning sickness.17 While far above nutritional needs, this dosage should be safe. However, for the treatment of other conditions, B 6 has been recommended at doses as high as 300 mg daily. There are potential risks at this level of vitamin B 6 intake. (See the Safety Issues section below for more information).
Therapeutic Uses TOP
Vitamin B 6 has been proposed for numerous other uses as well, but without much (if any) scientific substantiation. For example, the two most famous uses of vitamin B 6, carpal tunnel syndrome and premenstrual syndrome PMS, have no reliable supporting evidence at all, and the best-designed studies found it ineffective for either of these purposes.18,55
Higher intake of vitamin B 6 reduces the level of homocysteine in the blood, a substance that might accelerate cardiovascular disease (heart disease, strokes, and related conditions.) However, there is as yet no meaningful evidence that reducing homocysteine is beneficial, and considerable evidence that it is not. See the full Homocysteine article for more information.
A series of studies suggests that vitamin B 6 may be helpful for the treatment of TD. In the first study, a 4-week, double-blind crossover trial of 15 people, treatment with vitamin B 6 significantly improved TD symptoms as compared to placebo.51 Benefits were seen beginning at 1 week of treatment. The subsequent follow-up study tested the benefits of vitamin B 6 used over a period of 26 weeks in 50 people with tardive dyskinesia, and once again the supplement proved more effective than placebo.71
For the following other conditions, current evidence for benefit with vitamin B 6 remains incomplete and/or contradictory: allergy to monosodium glutamate (MSG), asthma,24,25depression,23diabetes of pregnancy,26HIV infection,27,28photosensitivity,32 preventing kidney stones,19-22schizophrenia,56,57,65seborrheic dermatitis,35tardive dyskinesia and other side effects of anti-psychotic drugs,29-31,51,66,67 and vertigo.33
Despite some claims in the media, vitamin B 6 has not shown benefit for enhancing mental function.68 Research investigating the benefits of B 6 (in combination with folate and vitamin B 12) as a potential treatment for cognitive decline due to Alzheimer’s disease (AD) has also shown disappointing results.74
One study failed to find B 6 at a dose of 50 mg daily helpful for rheumatoid arthritis (despite a general B 6 deficiency seen in people with this condition).70
What Is the Scientific Evidence for Vitamin B 6 ? TOP
Nausea and Vomiting
Vitamin B 6 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.38 A total of 342 pregnant women were given placebo or 30 mg of vitamin B 6 daily. Subjects then graded their symptoms by noting the severity of their nausea and recording the number of vomiting episodes. The women in the B 6 group experienced significantly less nausea than those in the placebo group, suggesting that regular use of B 6 can be helpful for morning sickness. However, vomiting episodes were not significantly reduced.
At least 3 studies have compared vitamin B 6 to ginger for the treatment of morning sickness. Two studies found them to be equally beneficial,69,72 while the other found ginger to be somewhat better.73 However, as ginger is not an established treatment for this condition, these studies alone do not provide any additional evidence in favor of B 6.
Chemotherapy-induced Nausea and Vomiting
Researchers also investigated whether vitamin B 6 can reduce the nausea and vomiting that often accompanies chemotherapy.75 One hundred and forty-two women with ovarian cancer who were undergoing chemotherapy were randomized into 3 groups: acupuncture plus B 6 injection into the P6 acupuncture point (located on the inside of the forearm, about 2 inches above the wrist crease), acupuncture alone, or B 6 alone. Those that received both acupuncture and B 6 experienced less nausea and vomiting compared to the other two groups.
Premenstrual Syndrome (PMS)
A recent, properly designed double-blind study of 120 women found no benefit of vitamin B 6 for PMS.39 In this study, three prescription drugs were compared against vitamin B 6 (pyridoxine, at 300 mg daily) and placebo. All study participants received 3 months of treatment and 3 months of placebo. Vitamin B 6 proved to be no better than placebo.
Approximately a dozen other double-blind studies have investigated the effectiveness of vitamin B 6 for PMS, but none were well designed; overall the evidence for any benefit is weak at best.40,41 Some books on natural medicine report that the negative results in some of these studies were due to insufficient B 6 dosage, but in reality there was no clear link between dosage and effectiveness.
However, preliminary evidence suggests that the combination of B 6 and magnesium might be more effective than either treatment alone.42
One double-blind, placebo-controlled crossover study found indications that very high doses of vitamin B 6 may produce beneficial effects in the treatment of autism.34 However, this study was small and poorly designed; furthermore, it used a dose of vitamin B 6 so high that it could cause toxicity.
It has been suggested that combining magnesium with vitamin B 6 could offer additional benefits, such as reducing side effects or allowing a reduced dose of the vitamin. However, the two reasonably well-designed studies using combined vitamin B 6 and magnesium have failed to find benefits.58-60 Therefore, it isn’t possible at present to recommend vitamin B 6 with or without magnesium as a treatment for autism.
A double-blind study of 76 children with asthma found significant benefit from vitamin B 6 after the second month of usage.43 Children in the vitamin B 6 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.44 The dosages of B 6 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 B 6 without medical supervision (see Safety Issues).
Safety Issues TOP
The safe upper levels for daily intake of vitamin B 652 are as follows:
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.45 (This is a bit ironic, given that B 6 deficiency also causes nerve problems.) In some cases, very high doses of vitamin B 6 can cause or worsen acne symptoms.46,47
In addition, doses of vitamin B 6 over 5 mg may interfere with the effects of the drug levodopa when it is taken alone.48-50 However, vitamin B 6 does not impair the effectiveness of drugs containing levodopa and carbidopa.
Maximum safe dosages for individuals with severe liver or kidney disease have not been established.
Interactions You Should Know About TOP
If you are taking:
References[ + ]
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Last reviewed December 2015 by EBSCO CAM Review Board
Last Updated: 12/15/2015
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