Vitamin B12 absorption and factors associated with the response to long-term oral B12 supplementation: a secondary analysis of data from a B12-deficient Indian rural community.

BACKGROUND

The absorption of oral vitamin B12 (B-12) and predictors of its long-term supplementation are not well understood in populations with B-12 insufficiency.

OBJECTIVE

In a secondary data analysis of a B-12 absorption study and a supplementation trial in a B-12 insufficient rural Indian community, we examined (i) the distribution of plasma holotranscobalamin (holoTC) responses during an absorption test, and (ii) predictors of B-12 status during long-term, oral supplementation with physiological and near-physiological doses of B-12.

METHODS

Participants in the Pune Maternal Nutrition Study first underwent a B-12 absorption study (CobaSorb protocol) and subsequently participated in a 12-month double-blind randomized controlled trial of daily oral B-12 (0, 2, or 10 µg cyanocobalamin) and folic acid (0 or 200 µg). Plasma holoTC responses during absorption test were characterized, and linear mixed-effects models used to identify predictors of B-12 absorption and response during long-term supplementation.

RESULTS

Participants (313) included children (n = 109, mean age 9 y, weight 21.9 kg, BMI 13.6 kg/m2), mothers (n = 108, 30 y, 47.7 kg, 19.3 kg/m2), and fathers (n = 96, 37 y, 59.3 kg, 21.4 kg/m2). The holoTC response during the absorption test was positively associated with the B-12 dose (10 or 2 µg) and negatively with body weight. Improvements in B-12 status (plasma B-12, tHcy, combined B-12 indicator: 2cB12) after supplementation were positively predicted by baseline biomarker concentration, holoTC response during absorption test, B-12 dose, and compliance.

CONCLUSIONS

The holoTC response during B-12 absorption test predicted subsequent biomarker responses to long-term B-12 supplementation, linking absorptive capacity with metabolic correction. These findings provide a mechanistic framework for understanding variability in response to oral B-12 replenishment.