The effect of retinyl palmitate added to iron-fortified maize porridge on erythrocyte incorporation of iron in African children with vitamin A deficiency

Retinyl palmitate added to Fe-fortified maize bread has been reported to enhance Fe absorption in adult Venezuelan subjects but not in Western Europeans. It is not known to what extent these results were influenced by differences in vitamin A status of the study subjects. The objective of the present study was to evaluate the influence of retinyl palmitate added to Fe-fortified maize porridge on erythrocyte incorporation of Fe in children with vitamin A deficiency, before and after vitamin A supplementation. Erythrocyte incorporation of Fe-stable isotopes was measured 14 d after intake of maize porridge (2·0 mg Fe added as ferrous sulfate) with and without added retinyl palmitate (3·5 (mu)mol; 3300 IU). The study was repeated 3 weeks after vitamin A supplementation (intake of a single dose of 210 (mu)mol retinyl palmitate; ‘vitamin A capsule’). Vitamin status was evaluated by the modified relative dose–response (MRDR) technique. Retinyl palmitate added to the test meal reduced the geometric mean erythrocyte incorporation of Fe at baseline from 4·0 to 2·6 % (P=0·008, n 13; paired t test). At 3 weeks after vitamin A supplementation, geometric mean erythrocyte incorporation was 1·9 and 2·3 % respectively from the test meal with and without added retinyl palmitate (P=0·283). Mean dehydroretinol:retinol molar ratios were 0·156 and 0·125 before and after intake of the single dose of 210 (mu)mol retinyl palmitate; ‘vitamin A capsule’ (P=0·15). In conclusion, retinyl palmitate added to the labelled test meals significantly decreased erythrocyte incorporation of Fe in children with vitamin A deficiency at baseline but had no statistically significant effect 3 weeks after vitamin A supplementation. The difference in response to retinyl palmitate added to Fe-fortified maize porridge on erythrocyte incorporation of Fe before and after intake of the vitamin A capsule indicates, indirectly, changes in vitamin A status not measurable by the MRDR technique. The lack of conclusive data on the effect of retinyl palmitate on Fe absorption indicates the complexity of the interactions between vitamin A status, dietary vitamin A and Fe metabolism.