Increases in plasma holotranscobalamin can be used to assess vitamin B-12 absorption in individuals with low plasma vitamin B-12

Bhat, Dattatray S., Thuse, Nileema V., Lubree, Himangi G., Joglekar, Charudatta V., Naik, Sadanand S., Ramdas, Lalita V., Johnston, Carole, Refsum, Helga, Fall, Caroline H. and Yajnik, Chittaranjan (2009) Increases in plasma holotranscobalamin can be used to assess vitamin B-12 absorption in individuals with low plasma vitamin B-12. Journal of Nutrition, 139 (11), 2119-2123. (doi:10.3945/jn.109.107359).

Abstract

Low plasma concentrations of vitamin B-12 are common in Indians, possibly due to low dietary intakes of animal-source foods. Whether malabsorption of the vitamin contributes to this has not been investigated. A rise in the plasma holotranscobalamin (holo-TC) concentration after a standard dose of oral vitamin B-12 has been proposed as a measure of gastrointestinal absorption in people with normal plasma vitamin B-12 concentrations. We studied 313 individuals (children and parents, 109 families) in the Pune Maternal Nutrition Study. They received 3 doses of 10 µg (n = 191) or 2 µg (n = 122) of cyanocobalamin at 6-h intervals. A rise in plasma holo-TC of 15% and >15 pmol/L above baseline was considered normal vitamin B-12 absorption. The baseline plasma vitamin B-12 concentration was <150 pmol/L in 48% of participants; holo-TC was <35 pmol/L in 98% and total homocysteine was high in 50% of participants (>10 µmol/L in children and >15 µmol/L in adults). In the 10 µg group, the plasma holo-TC concentration increased by 4.8-fold from (mean ± SD) 9.3 ± 7.0 pmol/L to 53.8 ± 25.9 pmol/L and in the 2 µg group by 2.2-fold from 11.1 ± 8.5 pmol/L to 35.7 ± 19.3 pmol/L. Only 10% of the participants, mostly fathers, had an increase less than the suggested cut-points. Our results suggest that an increase in plasma holo-TC may be used to assess vitamin B-12 absorption in individuals with low vitamin B-12 status. Because malabsorption is unlikely to be a major reason for the low plasma vitamin B-12 concentrations in this population, increasing dietary vitamin B-12 should improve their status.

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Contributors

Author: Caroline H. Fall

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