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Staging vitamin B-12 (cobalamin) status in vegetarians

By Victor Herbert


ABSTRACT When one stops eating vitamin B-l2 (cobala-mins), one passes through four stages of negative cobalamin bal-ance: serum depletion [low holotranscobalamin II, ic, low vita-mm B- 12 on transcobalamin II (TCII)], cell depletion (decreasing holohaptocorrin and low red cell vitamin B-12 concentrations), biochemical deficiency (slowed DNA synthesis, elevated serum homocysteine and methylmalonate concentrations), and, finally, clinical deficiency (anemia). Serum vitamin B- 12 is on two pro-teins: the circulating vitamin B-l2 delivery protein, TCII, and the circulating vitamin B- I 2 storage protein, haptocomn. Because TCII is depleted of vitamin B-l2 within days after absorption stops, the best screening test for early negative vitamin B- 12 balance is a measurement of vitamin B- 12 on TCII (holoTCil). Ho1oTCII falls below the bottom of its normal range long before total serum vitamin B- 12 (which is mainly vitamin B-12 on hap-tocomn) falls below the bottom of its normal range. Am J Clin Nutr l994;59(suppl): 12 l3S-22S. KEY WORDS Vitamin B-l2, serum holotranscobalamin II

Topics: serum holohaptocomn, B- 12 haptocomn, haptocorrin
Year: 1994
DOI identifier: 10.1093/ajcn/59.5.1213s
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