Benders'dictionary of nutrition and food technology

498dependent enzymes. The abnormality is corrected by the administrationof large supplements of vitamin B 6 .vitamin B 6 toxicity High intakes of supplements of vitamin B 6 ,in excess of 200–1000 mg/day (far in excess of what could beobtained from foods) cause peripheral sensory neuropathy.vitamin B 7 ,B 8 and B 9 In the early days of nutrition research, whena new factor was discovered that was claimed to be essential forchick growth and feathering, the claimant stated that since ninefactors were known the new factors should be called vitamins B 10and B 11 . In fact, the B vitamins had been numbered only up toB 6 , hence B 7 ,B 8 and B 9 have never existed. B 9 is sometimes(incorrectly) used for folic acid.vitamin B 10 and B 11 The names given to two factors claimed to beessential for chick growth and feathering; they were later shownto be a mixture of vitamin B 1 and folic acid.vitamin B 12 (see p. 499) Cobalamin; coenzyme for methioninesynthetase (EC 2.1.1.13, important in metabolism of folic acid),methylmalonyl CoA mutase (EC 5.4.99.2) and leucine aminomutase(EC 5.4.3.7).Deficiency leads to pernicious anaemia when immature redblood cells are released into the bloodstream, and there is degenerationof the spinal cord. The anaemia is the same as seen infolate deficiency, and is due to impairment of folate metabolism.There is also urinary excretion of methylmalonic acid.Absorption of vitamin B 12 requires intrinsic factor,a proteinsecreted in the gastric juice. Failure of absorption, rather thandietary deficiency, is the main cause of pernicious anaemia.However, B 12 is found only in animal foods so strict vegetariansare at risk.See also dump suppression test; methyl folate trap;schilling test.vitamin B 13 Orotic acid, an intermediate in pyrimidine synthesis;no evidence that it is a dietary essential; not a vitamin.vitamin B 14 Not an established vitamin; name originally given toa compound found in human urine that increases the rate of cellproliferation in bone marrow culture.vitamin B 15 pangamic acid; no evidence that it has any physiologicalfunction in the body; not a vitamin.vitamin B 16 This term has never been used.vitamin B 17 amygdalin (laetrile); no evidence that it has anyphysiological function in the body; not a vitamin.vitamin B C Obsolete name for folic acid.vitamin B D Called the antiperosis factor for chicks, but can bereplaced by manganese and choline (not a dietary essential forhuman beings).