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Vitamin B6, also known as pyridoxine, is an essential vitamin involved in protein metabolism. Deficiency, which is rare, can be induced by the tuberculosis drug isoniazid and manifests as an enlarged and painful tongue. Vitamin B6 toxicity is also rare and occurs in individuals who consume megadoses of vitamin B6, usually as a result of overzealous supplementing or medical treatment. Symptoms are neurologic.
Vitamin B6 is available in pill form, either as part of a multivitamin or on its own. It is a water-soluble vitamin, meaning excess amounts are excreted in the urine. However, long-term supplementation with very high doses may result in painful neurological symptoms, including pins-and-needles sensations, known as sensory neuropathy. To date, no studies have shown toxicity from daily intake at or below 200 mg per day. For safety, the tolerable upper intake level is 100 mg per day. Many supplements include this amount of B6.
- Vitamin B6 is available in pill form, either as part of a multivitamin or on its own.
- To date, no studies have shown toxicity from daily intake at or below 200 mg per day.
Folic Acid and Blood Clots
Megadoses of vitamin B6 in the amount of 500 mg per day are sometimes used for the treatment of certain conditions. These include carpal tunnel syndrome and premenstrual syndrome. Effectiveness of vitamin B6 for the treatment of any condition is unproven, according to the Merck Manuals Online Medical Library, and since a clear association between megadoses of vitamin B6 and neurologic symptoms exists, risks of supplementation may outweigh the benefits, so ask your doctor 2.
The recommended dietary allowance is of vitamin B6 is about 1.5 mg per day. Foods contain less vitamin B6 than supplements. Even fortified cereals, which are the highest in B6 of all foods, contain less than 5 mg per serving. Other foods high in B6 include chickpeas and fish. Eating large quantities of these foods is unlikely to produce symptoms of toxicity, since it may be impossible to achieve dietary levels approaching 100 mg per day without supplementation.
- The recommended dietary allowance is of vitamin B6 is about 1.5 mg per day.
- Even fortified cereals, which are the highest in B6 of all foods, contain less than 5 mg per serving.
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- Micronutrient Information Center: Linus Pauling Institute
- The Merck Manuals Online Medical Library
- Gummin DD, Mowry JB, Spyker DA, Brooks DE, Osterthaler MK. 2017 annual report of the American Association of Poison Control Centers’ National Poison Data System (NPDS): 35th annual report. Clinical Toxicology. 2018 Dec;56(12):1213-1415. doi:10.1080/15563650.2018.1533727
- Olson KR, Anderson IB, Benowitz NL et al. Poisoning and Drug Overdose, Seventh Edition. McGraw-Hill Education / Medical; 2017.
- National Institutes of Health Office of Dietary Supplements. Niacin fact sheeet for health professionals. Updated July 9, 2019.
- National Institutes of Health Office of Dietary Supplements. Vitamin B6 fact sheet for health professionals. Updated September 19, 2019.
- National Institutes of Health Office of Dietary Supplements. Vitamin C fact sheet for health professionals. Updated July 9, 2019.
- MedlinePlus. Hypervitaminosis D. Updated November 17, 2017.
- Klein EA, Thompson IM Jr, Tangen CM, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2011;306(14):1549–1556. doi:10.1001/jama.2011.1437
- Harvard Health Publishing. Listing of vitamins. Updated November 14, 2018.
- National Institutes of Health Office of Dietary Supplements. Vitamin A fact sheet for health professionals. Updated October 11, 2019.
- Ross CA. Encyclopedia of Dietary Supplements. Informa Healthcare, 2nd edition, 2010.
Adam Dave, M.D., has written both fiction and nonfiction since 1997. His most recent work, "The Paradigm Diet," a short course on applied nutrition, is available on Amazon. He holds a medical degree from Medical University of the Americas and trained in family medicine at the University of Colorado.