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User:Scarpy/Vitamin B6 Toxicity

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Megavitamin-B6 Syndrome
Other namesHypervitaminosis B6, Vitamin B6 Toxicity, Vitamin B6 Excess, Pyridoxine Neuropathy, Pyridoxine Intoxication

Megavitamin-B6 syndrome

Reference books

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  • International Dietetics and Nutrition Terminology (IDNT) Reference Manual, edition 4; ISBN #978-0-88091-467-3

Toxicity

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Adverse effects have been documented from vitamin B6 supplements, but never from food sources. Damage to the dorsal root ganglia is documented in human cases of overdose of pyridoxine.[1] Although it is a water-soluble vitamin and is excreted in the urine, doses of pyridoxine in excess of the dietary upper limit (UL) over long periods cause painful and ultimately irreversible neurological problems.[2] The primary symptoms are pain and numbness of the extremities. In severe cases, motor neuropathy may occur with "slowing of motor conduction velocities, prolonged F wave latencies, and prolonged sensory latencies in both lower extremities", causing difficulty in walking.[3] Sensory neuropathy typically develops at doses of pyridoxine in excess of 1,000 mg per day, but adverse effects can occur with much less, so doses over 200 mg are not considered safe.[4] Symptoms among women taking lower doses have been reported.[5]

Existing authorizations and valuations vary considerably worldwide. As noted, the U.S. Institute of Medicine set an adult UL at 100 mg/day.[2] The European Community Scientific Committee on Food defined intakes of 50 mg of vitamin B6 per day as harmful and established a UL of 25 mg/day.[6] The nutrient reference values in Australia and New Zealand recommend an upper limit of 50 mg/day in adults. "The same figure was set for pregnancy and lactation as there is no evidence of teratogenicity at this level. The UL was set based on metabolic body size and growth considerations for all other ages and life stages except infancy. It was not possible to set a UL for infants, so intake is recommended in the form of food, milk or formula." The ULs were set using results of studies involving long-term oral administration of pyridoxine at doses of less than 1 g/day.[2][5][7][8][9][10] "A no-observed-adverse-effect level (NOAEL) of 200 mg/day was identified from the studies of Bernstein & Lobitz (1988) and Del Tredici et al (1985). These studies involved subjects who had generally been on the supplements for five to six months or less. The study of Dalton and Dalton (1987), however, suggested the symptoms might take substantially longer than this to appear. In this latter retrospective survey, subjects who reported symptoms had been on supplements for 2.9 years, on average. Those reporting no symptoms had taken supplements for 1.9 years."[11]

See also

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References

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  1. ^ Schaumburg, Herbert; Kaplan, Jerry; Windebank, Anthony; Vick, Nicholas; Rasmus, Stephen; Pleasure, David; Brown, Mark J. (1983). "Sensory Neuropathy from Pyridoxine Abuse". New England Journal of Medicine. 309 (8): 445–448. doi:10.1056/NEJM198308253090801. ISSN 0028-4793. PMID 6308447.
  2. ^ a b c Institute of Medicine (1998). "Vitamin B6". Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. pp. 150–195. doi:10.17226/6015. ISBN 978-0-309-06554-2. LCCN 00028380. OCLC 475527045. PMID 23193625.
  3. ^ Foca FJ (September 1985). "Motor and sensory neuropathy secondary to excessive pyridoxine ingestion". Archives of Physical Medicine and Rehabilitation. 66 (9): 634–6. PMID 2994596.
  4. ^ Katan MB (November 2005). "[How much vitamin B6 is toxic?]". Nederlands Tijdschrift voor Geneeskunde. 149 (46): 2545–6. PMID 16320662.
  5. ^ a b Dalton, K.; Dalton, M. J. T. (1987). "Characteristics of pyridoxine overdose neuropathy syndrome". Acta Neurologica Scandinavica. 76 (1): 8–11. doi:10.1111/j.1600-0404.1987.tb03536.x. ISSN 0001-6314. PMID 3630649.
  6. ^ Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (2008). "Opinion on Pyridoxal 5′-phosphate as a source for vitamin B6 added for nutritional purposes in food supplements". The EFSA Journal. 760: 1–13. doi:10.2903/j.efsa.2008.760.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: url-status (link)
  7. ^ "More on Neuropathy from Pyridoxine Abuse". New England Journal of Medicine. 311 (15): 986–987. 1984. doi:10.1056/NEJM198410113111513. ISSN 0028-4793. PMID 6472427. {{cite journal}}: Unknown parameter |authors= ignored (help)
  8. ^ Dalton K (May 1985). "Pyridoxine overdose in premenstrual syndrome". Lancet. 1 (8438): 1168–9. doi:10.1016/S0140-6736(85)92480-8. PMID 2860378.
  9. ^ Del Tredici AM, Bernstein AL, Chinn K (1985). "Carpal tunnel syndrome and vitamin B6 therapy.". In Reynolds RD, Leklem JE (eds.). Vitamin B6: Its Role in Health and Disease. New York: Liss. pp. 459–462.
  10. ^ Parry, G. J.; Bredesen, D. E. (1985). "Sensory neuropathy with low-dose pyridoxine". Neurology. 35 (10): 1466–8. doi:10.1212/WNL.35.10.1466. ISSN 0028-3878. PMID 2993949.
  11. ^ "Vitamin B6". www..gov.au. 2014-03-17. Archived from the original on 2018-03-13. Retrieved 2018-04-20.
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