Human milk as a source of ascorbic acid: no enhancing effect on iron bioavailability from a traditional complementary food consumed by Bangladeshi infants and young children

BACKGROUND: Iron bioavailability from traditional complementary foods based on cereals and legumes can be expected to be low unless ascorbic acid-rich foods are incorporated into the diet. OBJECTIVE: We evaluated human milk as a source of ascorbic acid for enhancing iron bioavailability from khichuri, a complementary food based on rice and lentils. DESIGN: Erythrocyte incorporation of stable iron isotopes 14 d after administration was used as a proxy for iron bioavailability. Children aged 8-18 mo (n = 31) were breastfed (32-90 mg ascorbic acid/kg human milk) immediately after intake of 4 servings of khichuri labeled with (57)Fe (test meal B) and were offered water after intake of 4 servings of khichuri labeled with (58)Fe (test meal A). Test meals were fed twice daily during 4 d in the order of AABBAABB or BBAABBAA. RESULTS: The mean intakes of human milk and ascorbic acid were 274 g (range: 60-444 g) and 14 mg (range: 4-28 mg, respectively). The mean molar ratio of ascorbic acid to iron was 2.3 (range: 0.7-4.6). The geometric mean iron bioavailability from khichuri fed with or without human milk was 6.2% and 6.5%, respectively (P = 0.76, paired Student's t test). CONCLUSIONS: Although human milk contributed significant quantities of ascorbic acid, no significant difference in iron bioavailability was found between khichuri consumed with water and that consumed with human milk. These results indicate either that the molar ratio of ascorbic acid to iron was not sufficiently high to overcome the inhibitory effect of phytic acid in khichuri (30 mg/serving) or that components of human milk modified the influence of ascorbic acid on iron bioavailability.