Vitamin B-12 supplementation of rural mexican women changes biochemical vitamin B-12 status indicators but does not affect hematology or a bone turnover marker

Abstract

A high prevalence of low serum vitamin B-12 concentrations has been reported in studies and surveys in Latin America including Mexico, but the functional consequences are unknown. This randomized controlled trial assessed the response to a high-dose vitamin B-12 supplementation of women in rural Querétaro, Mexico. Participants aged 20-59 y were stratified at baseline to deficient, marginal, and adequate status groups (serum vitamin B-12, 75-148, 149-220, and >220 pmol/L, respectively), and each group was randomized to vitamin B-12 treatment (single dose of 1 mg i.m. then 500 μmg/d orally for 3 mo, n = 70) or placebo (n = 62). Measures at baseline and 3 mo included, complete blood count, serum vitamin B-12, holotranscobalamin (holoTC), folate, ferritin, C-reactive protein (CRP), bone alkaline phosphatase, and methylmalonic acid (MMA) and plasma total homocysteine (tHcy). At baseline, 11% of the women were vitamin B-12 deficient and 22% had marginal status. HoloTC was low (<35 pmol/L) in 23% and correlated with serum vitamin B-12 (r = 0.7, P < 0.001). Elevated MMA (>271 nmol/L) and tHcy (>12μmol/L) occurred in 21 and 31%, respectively, and correlated with serum vitamin B-12 (r =-20.28, P < 0.0007 and r =-20.20, P < 0.01, respectively). Supplementation increased serum vitamin B-12 and holoTC and lowered MMA and tHcy, normalizing all values except for elevated tHcy in 21% of the women. Supplementation did not affect hematology or bone-specific alkaline phosphatase. Vitamin B-12 supplementation normalized biochemical indicators of vitamin B-12 status in the treatment group but did not affect the functional outcomes measured. © 2012 American Society for Nutrition.