vitamin b6

Vitamin B6 is a water-soluble vitamin that occurs naturally in a wide range of foods (including fish, poultry, organ meats, starchy vegetables such as potatoes, and non-citrus fruit) and is also sold as a supplement, most commonly as pyridoxine. It serves as a cofactor in well over 100 enzyme reactions, chiefly in protein metabolism, and contributes to brain development in pregnancy and infancy as well as to normal immune function. In the United States most people meet their needs through diet, and clinical deficiency is uncommon.

Evidence differs markedly by use. The best-supported use is nausea and vomiting in pregnancy: drawing on several trials, the American College of Obstetricians and Gynecologists (ACOG) recommends vitamin B6 under a clinician's care for this purpose, although a Cochrane review of interventions for nausea and vomiting in pregnancy was unable to reach firm conclusions about its value. For PMS, NIH states that scientists are not yet certain about any benefit; some studies suggest it may lessen symptoms, but most were small or methodologically weak, and more research is needed before firm conclusions can be drawn. For heart disease and stroke, B vitamins do lower blood homocysteine, but NIH reports that the research to date provides little evidence they actually reduce the risk or severity of cardiovascular disease and stroke. Trials have not demonstrated that B6 supplements prevent cancer or reduce cancer mortality, and B6 (alone or combined with B12 and/or folic acid) does not appear to improve cognitive function or mood in healthy people or in people with dementia.

Recommended daily intake depends on age and life stage: roughly 1.3 mg for most adults, rising to 1.5 mg for women and 1.7 mg for men over 50, and 1.9 mg in pregnancy and 2.0 mg while breastfeeding. The Daily Value used on supplement labels is 1.7 mg. Doses studied for specific conditions are higher: for pregnancy nausea, ACOG suggests vitamin B6 monotherapy of 10-25 mg three or four times a day, which can approach the tolerable upper limit, so it should be used only under medical supervision. Talk to your doctor, pharmacist, or a registered dietitian before starting vitamin B6, especially at doses above the recommended daily amount, during pregnancy, or if you take other medications.

Getting too much vitamin B6 from food or drink is almost unheard of. The Tolerable Upper Intake Level from all sources is 100 mg/day for adults (lower for children and teens), and per NIH this limit does not apply to people taking B6 for a medical reason under a doctor's care. Some authorities are more cautious: in 2023 the European Food Safety Authority set a much lower upper limit of 12 mg/day for adults (and 2.2-10.7 mg/day for infants and children, by age). Pregnant or breastfeeding people, and anyone with a medical condition or on medication, should check with a clinician first.

Vitamin B6 from food has not been reported to cause harm. However, taking high supplemental doses for a year or longer can cause severe, progressive nerve damage (sensory neuropathy, marked by ataxia, or loss of control of bodily movements); NIH notes the severity appears dose-dependent and that symptoms usually subside once the supplements are stopped. Other reported effects of excess B6 include painful or disfiguring skin lesions, heightened sensitivity to sunlight, nausea, and heartburn.

Vitamin B6 supplements can interact with several medications. They may interact with the tuberculosis antibiotic cycloserine (Seromycin) and worsen the seizures and nerve-cell damage the drug can cause. Some antiepileptic drugs, including valproic acid, carbamazepine, and phenytoin, can lower B6 levels; in turn, B6 supplementation may reduce blood levels of certain seizure medicines (such as phenytoin) and the drugs' ability to control seizures. The asthma and lung medication theophylline can also lower B6 levels and may contribute to seizures. Tell your doctor and pharmacist about all supplements and medicines you take so they can check for interactions.