Evaluation of biochemical indicators of vitamin A status in breast-feeding and non-breast-feeding Indonesian women

Indicators of vitamin A status were evaluated in nonpregnant breast-feeding (n = 265) and nonpregnant non-breast-feeding (n = 49) Indonesian women. The concentration of vitamin A (not including provitamin A carotenoids) and fat in breast milk was 30% and 20% higher, respectively, for women with a breast-fed child 7-18 mo old than for women with an infant 3-6 mo old. The vitamin A content of milk fat was constant throughout lactation. Breast-milk vitamin A was most sensitive to changes in vitamin A status when expressed per volume. Sensitivity and specificity for detecting serum retinol concentrations < 0.70 mu mol/L were < 75% for the concentration of breast-milk vitamin A and serum retinol binding protein (REP). The modified-relative-dose-response (MRDR) method suffers from a relatively large intraindividual variation in the ratio of dehydroretinol to retinol because of vulnerability of the dehydroretinol concentration to laboratory errors and to variation in dosing and absorption. Within categories of dehydroretinol:retinol, serum retinol concentration was lower in breast-feeding women than in non-breastfeeding women. Thus, it may be necessary to use different cutoff values for the ratio and for serum retinol concentration. Serum retinol concentration, which was just above marginal (0.85 mu mol/L), had the smallest within-person variation and was also the most sensitive indicator for detecting a difference between groups in change in vitamin A status postintervention, requiring only 19 subjects per group. Serum REP concentration, breast-milk vitamin A expressed per volume or per gram milk fat, and the MRDR method required groups of 35, 36, 139, and 53 subjects, respectively.