Bottom Line: Vitamin B6 does not appear to be an effective treatment for asthma, circulatory disorders, or PMS. Whether it is helpful in heart disease, carpal tunnel syndrome, diabetic neuropathy, or high blood pressure requires further study. It may be able to relieve nausea and vomiting during pregnancy.
Vitamin B6 is necessary for over 100 physiological processes in the human body. These include reactions of cellular respiration, the release of glucose stores, and amino acid metabolism. In conditions in which this vitamin is depleted from the body, vitamin B6 supplements are thought to be helpful. Although scientists are very familiar with the normal role of vitamin B6 in the body, it is not known if extra B6 will have any benefits.
To treat alcoholism Alcoholism can lead to deficiency in vitamin B6 and many other nutrients, so supplementation may help to improve nutritional status.
To treat asthma One clinical trial does not support this use.
To manage heart disease Clinical studies show inconsistent results.
To treat carpal tunnel syndrome Some preliminary clinical trials support this use, but further research is needed.
To manage circulatory disorders No scientific evidence supports this use.
To treat diabetes Clinical studies show inconsistent results.
To treat homocystinuria Pyroxidine (vitamin B6) is currently used as a mainstream treatment for homocystinuria.
To lower high blood pressure Clinical studies show inconsistent results.
To stimulate the immune system No scientific evidence supports this use.
To treat pregnancy-related nausea and vomiting A few clinical trials support this use.
To treat the symptoms of premenstrual syndrome (PMS) Clinical studies show inconsistent results.
To treat palmar-plantar erythrodyesthesia Some preliminary clinical trials support this use, but further research is needed.
Palmar-plantar erythrodysesthesia (PPE): The chemotherapy drug 5-fluorouracil can often cause palmar-plantar erythrodysesthesia (PPE) as a side effect. The ability of 50 or 150 mg of vitamin B6 (pyridoxine) daily to treat PPE was tested in five patients who were beginning to develop its symptoms from 5-fluorouracil (5-FU). Four out of five patients experienced an improvement in their symptoms, and were able to continue 5-FU therapy for a longer time than patients not taking vitamin B6. These results are promising, but larger clinical trials would help support this use of vitamin B6.
Diabetic neuropathy: Peripheral neuropathy is a common complication of diabetes. A small clinical trial assessed the use of vitamin B6 for the treatment of diabetic neuropathy. Eighteen diabetic patients enrolled; nine were given 50 mg of pyridoxine every eight hours, the other nine were given a placebo pill every eight hours. Six of the patients taking vitamin B6 and four taking placebo reported improvements in their symptoms, indicating that vitamin B6 did not have a huge effect. Nerve conduction tests were performed on all patients and showed that vitamin B6 did not improve nerve firing, either. However, because these groups are so small, it is difficult to see an effect from vitamin B6, and larger clinical trials are needed.
This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
Paresthesias (numbness, tingling, or burning in the hands and feet)
Toxicity: Chronic intake of vitamin B6 (200 mg or greater per day) may result in severe peripheral sensory nerve problems, ataxia (failure of muscular coordination), respiratory difficulties, profound sedation, and vomiting. Toxicities appear to be reversible once vitamin B6 is discontinued.
Pyridoxine hydrochloride, pyridoxal, pyridoxamine, pyridoxic acid, and the phosphorylated forms pyridoxal phosphate (PLP), pyridoxamine phosphate (PMP), and pyridoxine phosphate (PNP)
Vitamin B6, or pyridoxine, is a water-soluble vitamin and a coenzyme in the folate metabolism pathway. Phosphorylated metabolites of pyridoxine are involved in amino acid metabolism, the transsulfuration pathway of homocysteine to cysteine, and glycogen phosphorylase, which mobilizes glucose from glycogen (2). Vitamin B6 is abundant in meats, fish, poultry, shellfish, leafy green vegetables, legumes, fruits, and whole grains. Patients use vitamin B 6 for heart disease, hypertension, peripheral neuropathies, carpal tunnel syndrome, and diabetes. Preliminary data suggest that vitamin B6 may be of benefit for palmar-plantar erythrodysesthesia (PPE) (5) and carpal tunnel syndrome (7)(8), but additional studies are necessary. Studies of its efficacy in diabetes (6), heart disease (9)(10), premenstrual syndrome (11)(12)(13), and hypertension (14) show inconsistent results. Vitamin B6 supplementation was not effective in improving cognition in older adults (18).
Current data suggest a beneficial role of vitamin B6 in preventing colorectal cancer (15), (16). However, conclusions from the Women's Health Study indicate that supplementation with vitamins B6, B12, and folate did not decrease the risk of breast cancer (17) and a recent study reported that a combination of folate and vitamins B6 and B12 did not have an effect on overall risk of invasive cancer or breast cancer (19).
Infrequent adverse events include headache, nausea, sedation, and mild paresthesias (3). Chronic consumption of large doses may cause severe neuropathies, ataxia, respiratory difficulties, and profound sedation, although reversal usually occurs following discontinuation (4).
Vitamin B6 is a water-soluble vitamin. It exists as an alcohol (pyridoxine, PN), aldehyde (pyridoxal, PL), or amine (pyridoxamine, PM). Pyridoxal-P (PLP), phosphorylated pyridoxal, is the major coenzyme form and the most abundant in animal tissue. PLP is the cofactor for over 100 enzymes used in amino acid metabolism, including aminotransferases, decarboxylases, racemases, and dehydrases. In particular, it acts as a coenzyme for cystathionine B-synthase and cystathionase in the transsulfuration pathway from homocysteine to cysteine. It also facilitates mobilization of glucose units from glycogen via glycogen phosphorylase. (3)
Absorption: Vitamin B6 is absorbed by nonsaturable passive diffusion. Absorption in the gut involves phosphatase-mediated hydrolysis followed by passive transport of the nonphosphorylated form into the mucosal cell (3). Distribution/Metabolism: Most of absorbed B6 is then phosphorylated to pyridoxal phosphate (PLP). PLP is the major form of the vitamin in plasma, where it is bound primarily to albumin. Nonphosphorylated B6 is distributed by erythrocytes. The bulk of B6 stores are in muscle (2) . Excretion: Elimination half-life is estimated to be 15-25 days. Metabolites of B6 are excreted primarily in the urine as 4-pyridoxic acid (4-PA). Other forms of the vitamin are also found in urine to a lesser extent. B6 is also excreted in the feces, but microbial synthesis of B6 in the lower gut makes it difficult to evaluate the extent of excretion (3).
Infrequent: Headache, drowsiness, mild flushing, and paresthesias Toxicity: Chronic dosing of vitamin B6 (200 mg and greater) may result in severe peripheral sensory neuropathies, ataxia, respiratory difficulties, profound sedation, and vomiting. Toxicities appear reversible following discontinuation. (3)(4)
None known. However, isoniazid, levodopa, alcoholism, and possibly oral contraceptives may reduce circulating plasma levels of vitamin B6 and its metabolites (3).
Lin J, Lee IM, Cook NR, et al. Plasma folate, vitamin B-6, vitamin B-12, and risk of breast cancer in women. Am J Clin Nutr. 2008;87(3):734-43. This is a prospective study to evaluate any association between plasma concentrations of folate, vitamin B6 and B12 and risk of breast cancer. Researchers identified 848 cases of invasive breast cancer and 848 matched control subjects, aged >/=45 years, from the Women's Health Study. Results showed that plasma levels of folate and vitamins B6 and B12 were not associated with overall risk of breast cancer. Therefore, supplementation with vitamins B6, B12, and folate may not reduce the risk of developing breast cancer. More studies are warranted.
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington (DC): National Academy Press; 2000.
Pronsky ZM. Power's and Moore's Food-Medication Interactions, 11th ed. Pottstown (PA): Food Medication Interactions; 2000.
