Addition of rice cereal to formula does not impair mineral bioavailability

Background: The effect of adding rice cereal to formula on calcium and iron bioavailability was studied. Methods: Fourteen healthy infants were studied at 2-week in tervals to assess the absorption of calcium and iron from formula or formula mixed with rice cereal. Infants were randomly assigned to initiate the study either on a lactose-containing formula (F) or the same formula mixed with 6.5 g/dl of rice cereal (F + R). Calcium and iron absorption were determined using a multiple tracer approach in which calcium and iron isotopes were given orally mixed with either F or F + R and a different tracer of calcium given intravenously. Nine infants underwent calcium and iron studies and five underwent calcium studies only. A tracer amount of Ca-46 was administered intravenously. Calcium absorption was determined as the ratio of the recovered oral versus intravenous tracer in the urine during the 24 hr after tracer administration. Iron incorporation into red blood cells (RBCs) was determined from the enrichment of the iron isotopes in the RBCs at 14 days after dosing. Results: Mean (+/-SD) percent absorption of calcium from F was 58% (+/-13) and from F + R 57% (+/-18). Absorption of iron from F was 5.8% (+/-7) and from F + R 6.3% (+/-4) (p = 0.06). Analyses of variance for repeated measures indicated no significant correlation between amount of calories, calcium, or iron ingested, and calcium or iron absorbed. Conclusions: Adding rice cereal to formula does not impair bioavailability of calcium or iron from infant formulas. Because of the increased total calcium and iron in the mixture of formula and cereal, the overall amount of minerals absorbed from F + R may be greater than from formula alone.