Vitamin B6 Overview

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:

• 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 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), ⁵ penicillamine (used for rheumatoid arthritis and certain rare diseases), ⁶ theophylline (an older drug for asthma), ^{7 8 9 10} MAO inhibitors , ¹¹ and the antituberculosis drug isoniazid (INH), ^{12 13 14} 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.

One study found that 30 mg of vitamin B 6 daily was effective for symptoms of morning sickness. ¹⁵ 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).

Morning Sickness (Nausea and Vomiting in Pregnancy)

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. ¹⁶ 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, ¹⁷ while the other found ginger to be somewhat better. ¹⁸ 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 .

Premenstrual Syndrome (PMS)

A recent, properly designed double-blind study of 120 women found no benefit of vitamin B 6 for PMS. ¹⁹ 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. ²⁰ 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. ²¹

Autism

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 . ²² 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. ^{23 24} Therefore, it isn’t possible at present to recommend vitamin B 6 with or without magnesium as a treatment for autism.

Asthma

A double-blind study of 76 children with asthma found significant benefit from vitamin B 6 after the second month of usage. ²⁵ 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 notshow any benefit. ²⁶ 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).

1. Kant AK, Block G. Dietary vitamin B-6 intake and food sources in the US population: NHANES II, 1976-1980. Am J Clin Nutr. 52(4):707-16.
2. van der Wielen RP, de Groot LC, van Staveren WA. Dietary intake of water soluble vitamins in elderly people living in a Western society (1980-1993). Nutr Res. 1994;14:605-638.
3. Albertson AM, Toblemann RC, Engstrom A, et al. Nutrient intakes of 2- to 10-year-old American children: 10-year trends. J Am Diet Assoc. 1992;92:1492-1496.
4. Hansen CM, Shultz TD, Kwak HK, Memon HS, Leklem JE. Assessment of vitamin B-6 status in young women consuming a controlled diet containing four levels of vitamin B-6 provides an estimated average requirement and recommended dietary allowance. J Nutr. 131(6):1777-86.
5. Vidrio H. Interaction with pyridoxal as a possible mechanism of hydralazine hypotension. J Cardiovasc Pharmacol. 15(1):150-6.
6. Rumsby PC, Shepherd DM. The effect of penicillamine on vitamin B6 function in man. Biochem Pharmacol. 30(22):3051-3.
7. Delport R, Ubbink JB, Serfontein WJ, Becker PJ, Walters L. Vitamin B6 nutritional status in asthma: the effect of theophylline therapy on plasma pyridoxal-5'-phosphate and pyridoxal levels. Int J Vitam Nutr Res. 58(1):67-72.
8. Ubbink JB, Vermaak WJ, Delport R, Serfontein WJ, Bartel P. The relationship between vitamin B6 metabolism, asthma, and theophylline therapy. Ann N Y Acad Sci. 585():285-94.
9. Delport R, Ubbink JB, Vermaak WJ, et al. Theophylline increases pyridoxal kinase activity independently from vitamin B 6 nutritional status. Res Commun Chem Pathol Pharmacol. 1993;79:325-333.
10. Ubbink JB, Delport R, Bissbort S, Vermaak WJ, Becker PJ. Relationship between vitamin B-6 status and elevated pyridoxal kinase levels induced by theophylline therapy in humans. J Nutr. 120(11):1352-9.
11. Heller CA, Friedman PA. Pyridoxine deficiency and peripheral neuropathy associated with long-term phenelzine therapy. Am J Med. 75(5):887-8.
12. Goldman AL, Braman SS. Isoniazid: a review with emphasis on adverse effects. Chest. 62(1):71-7.
13. Heller CA, Friedman PA. Pyridoxine deficiency and peripheral neuropathy associated with long-term phenelzine therapy. Am J Med. 75(5):887-8.
14. Biehl JP, Vilter RW. Effect of isoniazid on vitamin B 6 metabolism; its possible significance in producing isoniazid neuritis. Proc Soc Exp Biol Med. 1954;85:389-392.
15. Vutyavanich T, Wongtra-ngan S, Ruangsri R. Pyridoxine for nausea and vomiting of pregnancy: a randomized, double-blind, placebo-controlled trial. Am J Obstet Gynecol. 173(3 Pt 1):881-4.
16. Vutyavanich T, Wongtra-ngan S, Ruangsri R. Pyridoxine for nausea and vomiting of pregnancy: a randomized, double-blind, placebo-controlled trial. Am J Obstet Gynecol. 173(3 Pt 1):881-4.
17. Sripramote M, Lekhyananda N. A randomized comparison of ginger and vitamin B 6 in the treatment of nausea and vomiting of pregnancy. J Med Assoc Thai. 2003;86:846-53.
18. Ensiyeh J, Sakineh MA. Comparing ginger and vitamin B 6 for the treatment of nausea and vomiting in pregnancy: a randomised controlled trial. Midwifery. 2008 Feb 11.
19. Diegoli MS, da Fonseca AM, Diegoli CA, Pinotti JA. A double-blind trial of four medications to treat severe premenstrual syndrome. Int J Gynaecol Obstet. 62(1):63-7.
20. Kleijnen J, Ter Riet G, Knipschild P. Vitamin B6 in the treatment of the premenstrual syndrome--a review. Br J Obstet Gynaecol. 97(9):847-52.
21. De Souza MC, Walker AF, Robinson PA, Bolland K. A synergistic effect of a daily supplement for 1 month of 200 mg magnesium plus 50 mg vitamin B6 for the relief of anxiety-related premenstrual symptoms: a randomized, double-blind, crossover study. J Womens Health Gend Based Med. 9(2):131-9.
22. Rimland B, Callaway E, Dreyfus P. The effect of high doses of vitamin B6 on autistic children: a double-blind crossover study. Am J Psychiatry. 135(4):472-5.
23. Nye C, Brice A. Combined vitamin B6-magnesium treatment in autism spectrum disorder (Cochrane Review). Cochrane Database Syst Rev. 2002;CD003497.
24. Findling RL, Maxwell K, Scotese-Wojtila L, Huang J, Yamashita T, Wiznitzer M. High-dose pyridoxine and magnesium administration in children with autistic disorder: an absence of salutary effects in a double-blind, placebo-controlled study. J Autism Dev Disord. 27(4):467-78.
25. Collipp PJ, Goldzier S III, Weiss N, et al. Pyridoxine treatment of childhood bronchial asthma. Ann Allergy. 1975;35:93-97.
26. Sur S, Camara M, Buchmeier A, Morgan S, Nelson HS. Double-blind trial of pyridoxine (vitamin B6) in the treatment of steroid-dependent asthma. Ann Allergy. 70(2):147-52.