Evaluation of serum retinol, the modified-relative-dose-response ratio, and breast-milk vitamin A as indicators of response to postpartum maternal vitamin A supplementation

Background: Conflicting results have been reported regarding the relative p erformance of serum retinol, the modified-relative-dose-response (MRDR) rat io, and breast-milk vitamin A concentrations in detecting changes in matern al vitamin A status. Objective: We used receiver operating characteristic analyses and standardi zed differences to compare the ability of these indicators to detect a resp onse to postpartum vitamin A supplementation in lactating Bangladeshi women . Design: At 2 wk postpartum, women were randomly assigned to receive either a single dose of vitamin A [200000 IU (60000 retinol equivalents): n = 74] or placebo (n = 73). Data from maternal serum and breast milk collected 3 m o postpartum and from infant serum collected 6 mo postpartum were used to e xamine the ability of serum retinol, the MRDR ratio, and breast-milk vitami n A to discriminate between individuals in the supplemented and unsupplemen ted groups. Breast milk was collected by expressing the entire contents of one breast that had not been used to feed an infant for greater than or equ al to 2 h (full samples) or without controlling the time since the last bre ast-feeding episode (casual samples). Results: Casual breast-milk samples performed better than full breast-milk samples in detecting a response to maternal supplementation. The MRDR ratio performed better than serum retinol in both the women and their infants. O verall, the most responsive indicator was the measurement of breast-milk vi tamin A per of fat in casual breast-milk samples. gram or rat In casual bre ast-milk samples. Conclusions: Breast-milk vitamin A and the MRDR ratio an responsive indicat ors of vitamin A status, especially in women with mild vitamin A deficiency .