Vitamin B6 (Pyridoxine)
Description and function
Vitamin B6 is used to designate pyridoxine as well as various similar molecules that have comparable activity (e.g., pyridoxal, pyridoxamin and others).
It acts as a coenzyme (or cofactor) for an important number of enzymes and metabolic reactions in cells. As such, it is involved in the metabolism of amino acids; in the metabolism of proteins, lipids and carbohydrates; in the metabolism of other vitamins; in various nervous system functions (e.g., in the synthesis of neurotransmitters); in the development of antibodies; and many other functions.
Deficiency
Mild deficiencies may lead to increased blood levels of homocysteine, which constitutes an important risk factor for coronary artery disease and stroke. More severe deficiency may lead to cheilosis (inflammation and fissured of lips and corners of the mouth), seborrheic dermatitis, anemia, glossitis (reddening and burning of the tongue), irritability, depression, neuropathy and convulsions.
Sources
Good sources of vitamin B6 are meats, poultry, fish, whole grain cereals, nuts, seeds, potatoes, bananas and avocados. It is also available in the form of multivitamins.
Toxicity
Toxicity has been described with acute intakes of high dosages of vitamin B6 (e.g., 2 gm per day) or with chronic intakes of as low as 200 mg per day. Signs and symptoms of toxicity include ataxia (impaired muscular and movement coordination leading to unsteady gait), sensory and peripheral neuropathies (impaired position and proprioception sensation; numbness and tingling in extremities).
As vitamin B6 may interfere with some drugs, it is recommended to consult with your health care provider if you are on any medication and want to take supplements of vitamin B6.
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Scientific references
Books
Vitamin B6. Dakshinamurti S, Dakshinamurti K. In: Zempleni J, Rucker RB, McCormick DB, Suttie JW, eds. Handbook of Vitamins. 4th ed. New York: CRC Press (Taylor & Fracis Group); 2007:315-359.
Vitamin B6. Leklem JE. In: Machlin L, ed. Handbook of Vitamins. New York: Marcel Decker Inc; 1991:341-378.
Vitamin B6. Mackey AD, Davis SR, Gregory JF, 3rd. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease. 10th ed. Philadelphia: Lippincott Williams & Wilkins; 2006:452-461.
Vitamin B6. McCormick DB. In: Bowman BA, Russell RM, eds. Present Knowledge in Nutrition. Vol. I. Washington, D.C.: International Life Sciences Institute; 2006:269-277.
PDR for Nutritional Supplements. Hendler SS, Rorvik DR, eds. Montvale: Medical Economics Company, Inc; 2001.
Vitamin B6. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Food and Nutrition Board, Institute of Medicine. Washington D.C.: National Academies Press; 1998:150-195. (National Academies Press)
Scientific articles
A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. J Urol. 1996;155(6):1847-1851.
[Abstract]
A quantitative assessment of plasma homocysteine as a risk factor for vascular disease. Probable benefits of increasing folic acid intakes. Boushey CJ, Beresford SA, Omenn GS, Motulsky AG. JAMA. 1995;274(13):1049-1057.
[Abstract]
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. Hansen CM, Shultz TD, Kwak HK, Memon HS, Leklem JE. J Nutr. 2001;131(6):1777-1786.
[Abstract]
B vitamins, homocysteine, and neurocognitive function in the elderly. Selhub J, Bagley LC, Miller J, Rosenberg IH. Am J Clin Nutr. 2000;71(2):614S-620S.
[Abstract]
Clinical results of a cross-over treatment with pyridoxine and placebo of the carpal tunnel syndrome. Ellis J, Folkers K, Watanabe T, et al. Am J Clin Nutr. 1979;32(10):2040-2046.
[Abstract]
Effect of vitamin B6 on the side effects of a low-dose combined oral contraceptive. Villegas-Salas E, Ponce de Leon R, Juarez-Perez MA, Grubb GS. Contraception. 1997;55(4):245-248.
[Abstract]
Efficacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic review. Wyatt KM, Dimmock PW, Jones PW, Shaughn O'Brien PM. Bmj. 1999;318(7195):1375-1381.
[Abstract]
Folate and vitamin B6 from diet and supplements in relation to risk of coronary heart disease among women. Rimm EB, Willett WC, Hu FB, et al. JAMA. 1998;279(5):359-364.
[Abstract]
Hyperhomocysteinemia and low pyridoxal phosphate. Common and independent reversible risk factors for coronary artery disease. Robinson K, Mayer EL, Miller DP, et al. Circulation. 1995;92(10):2825-2830.
[Abstract]
Intake of vitamins B6 and C and the risk of kidney stones in women. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. J Am Soc Nephrol. 1999;10(4):840-845.
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Interventions for nausea and vomiting in early pregnancy. Jewell D, Young G. Cochrane Database Syst Rev. 2002(1):CD000145.
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Low circulating folate and vitamin B6 concentrations: risk factors for stroke, peripheral vascular disease, and coronary artery disease. European COMAC Group. Robinson K, Arheart K, Refsum H, et al. Circulation. 1998;97(5):437-443.
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Low pyridoxal 5'-phosphate is associated with increased risk of coronary artery disease. Lin PT, Cheng CH, Liaw YP, Lee BJ, Lee TW, Huang YC. Nutrition. 2006;22(11-12):1146-1151.
[Abstract]
Non-nutritional uses of vitamin B6. Bender DA. Br J Nutr. 1999;81(1):7-20
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Prospective study of coronary heart disease incidence in relation to fasting total homocysteine, related genetic polymorphisms, and B vitamins: the Atherosclerosis Risk in Communities (ARIC) study. Folsom AR, Nieto FJ, McGovern PG, et al. Circulation. 1998;98(3):204-210.
[Abstract]
Pyridoxine for nausea and vomiting of pregnancy: a randomized, double-blind, placebo-controlled trial. Vutyavanich T, Wongtra-ngan S, Ruangsri R. Am J Obstet Gynecol. 1995;173(3 Pt 1):881-884.
[Abstract]
Pyridoxine supplementation: effect on lymphocyte responses in elderly persons. Talbott MC, Miller LT, Kerkvliet NI. Am J Clin Nutr. 1987;46(4):659-664.
[Abstract]
Relations of vitamin B-12, vitamin B-6, folate, and homocysteine to cognitive performance in the Normative Aging Study. Riggs KM, Spiro A, 3rd, Tucker K, Rush D. Am J Clin Nutr. 1996;63(3):306-314.
[Abstract]
Short-term folate, vitamin B-12 or vitamin B-6 supplementation slightly affects memory performance but not mood in women of various ages. Bryan J, Calvaresi E, Hughes D. J Nutr. 2002;132(6):1345-1356.
[Abstract]
The role for vitamin B-6 as treatment for depression: a systematic review. Williams AL, Cotter A, Sabina A, Girard C, Goodman J, Katz DL. Fam Pract. 2005;22(5):532-537.
[Abstract]
Using pyridoxine to treat carpal tunnel syndrome. Randomized control trial. Spooner GR, Desai HB, Angel JF, Reeder BA, Donat JR. Can Fam Physician. 1993;39:2122-2127.
[Abstract]
Vitamin B-6 deficiency impairs interleukin 2 production and lymphocyte proliferation in elderly adults. Meydani SN, Ribaya-Mercado JD, Russell RM, Sahyoun N, Morrow FD, Gershoff SN. Am J Clin Nutr. 1991;53(5):1275-1280.
[Abstract]
Vitamin B6 deficiency in patients with a clinical syndrome including the carpal tunnel defect. Biochemical and clinical response to therapy with pyridoxine. Ellis JM, Kishi T, Azuma J, Folkers K. Res Commun Chem Pathol Pharmacol. 1976;13(4):743-757.
[Abstract]
Vitamin B6 in the treatment of the premenstrual syndrome--a review. Kleijnen J, Ter Riet G, Knipschild P. Br J Obstet Gynaecol. 1990;97(9):847-852.
[Abstract]
Vitamin B6 is effective therapy for nausea and vomiting of pregnancy: a randomized, double-blind placebo-controlled study. Sahakian V, Rouse D, Sipes S, Rose N, Niebyl J. Obstet Gynecol. 1991;78(1):33-36.
[Abstract]
Vitamin B-6 requirement and status assessment: young women fed a depletion diet followed by a plant- or animal-protein diet with graded amounts of vitamin B-6. Kretsch MJ, Sauberlich HE, Skala JH, Johnson HL. Am J Clin Nutr. 1995;61(5):1091-1101.
[Abstract]
Vitamin B-6 requirements of elderly men and women. Ribaya-Mercado JD, Russell RM, Sahyoun N, Morrow FD, Gershoff SN. J Nutr. 1991;121(7):1062-1074.
[Abstract]
Vitamin B-6 status of women with a constant intake of vitamin B-6 changes with three levels of dietary protein. Hansen CM, Leklem JE, Miller LT. J Nutr. 1996;126(7):1891-1901.
[Abstract]
Vitamin B-6 supplementation in elderly men: effects on mood, memory, performance and mental effort. Deijen JB, van der Beek EJ, Orlebeke JF, van den Berg H. Psychopharmacology (Berl). 1992;109(4):489-496.
[Abstract]
Vitamin B6, B12, and folic acid supplementation and cognitive function: a systematic review of randomized trials. Balk EM, Raman G, Tatsioni A, Chung M, Lau J, Rosenberg IH. Arch Intern Med. 2007;167(1):21-30.
[Abstract]
Vitamin B6, vitamin C, and carpal tunnel syndrome. A cross-sectional study of 441 adults. Keniston RC, Nathan PA, Leklem JE, Lockwood RS. J Occup Environ Med. 1997;39(10):949-959.
[Abstract]
Vitamin requirements for the treatment of hyperhomocysteinemia in humans. Ubbink JB, Vermaak WJ, van der Merwe A, Becker PJ, Delport R, Potgieter HC. J Nutr. 1994;124(10):1927-1933.
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