Distribution of Vitamin B12 Absorption in a Community and Factors Associated with the Response to Long-term Oral Supplementation

BACKGROUND Insufficient dietary intake and/or reduced gastrointestinal absorption lead to low vitamin B12 (B-12) status. OBJECTIVE In a secondary data analysis of a B-12 absorption (CobaSorb) study and a B-12 supplementation trial in a B-12 insufficient Indian rural community, we examined i) the distribution of plasma holo-transcobalamin (holoTC) response during the CobaSorb test, and ii) determinants of plasma B-12 response to long-term, oral supplementation with ‘physiological doses’ of B-12. METHODS The participants in the Pune Maternal Nutrition Study first underwent a B-12 absorption study (CobaSorb protocol). Subsequently, they participated in a 12-month-long, double-blind RCT of daily oral B-12 (0, 2, or 10 µg) and folic acid (0 or 200 µg). We studied distribution of plasma holoTC response in the CobaSorb test, and used linear mixed-effect model to determine predictors of B-12 absorption and response to supplementation. RESULTS Participants (313) included children (n = 109, 57 boys, mean age 9y, weight 21.9 kg, BMI 13.6 kg/m ² ), mothers (n = 108, 30y, 47.7 kg, 19.3 kg/m ² ), and fathers (n = 96, 37y, 59.3 kg, 21.4 kg/m ² ). The plasma holoTC response during the absorption test was continuously distributed and was negatively associated with weight and positively with the dose of B-12 (10 or 2 µg). Response to long-term B-12 supplementation was positively predicted by absorption test response, dose of B-12, length of supplementation, and compliance. CONCLUSIONS The continuous distribution of plasma holoTC response during the absorption test supports physiological absorption of B-12 in a community. CobaSorb protocol could be used to unravel the intricacies of B-12 absorption.