Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2001
Publication Date: 8/20/2002
Citation: ABRAMS, S.A., GRIFFIN, I.J., DAVILA, P.M. CALCIUM AND ZINC ABSORPTION FROM LACTOSE-CONTAINING AND LACTOSE-FREE INFANT FORMULAS 1-4. AMERICAN JOURNAL OF CLINICAL NUTRITION. 2002. v. 76(2). p. 442-446.
Interpretive Summary: Some parents feed their infants a lactose-free formula because they think their babies will be able to digest it better than one that contains lactose. Although these infants show growth comparable to that of infants fed lactose-containing formulas, questions remain regarding the mineral bioavailability and optimal mineral content of these lactose-free formulas. Although calcium absorption is enhanced by lactose, the ultimate significance of this effect in infant formula is uncertain, as is the effect of lactose on zinc absorption. Therefore, we assessed the absorption of calcium and zinc, using a multitracer, stable isotope approach, in full-term infants averaging 11 weeks of age, who were fed two different formulas; one contained lactose, while the other was lactose-free. The results indicate that the absence of lactose from a cow's milk-based formula leads to decreased calcium, but not zinc, bioavailability. However, absorption is sufficient to meet the calcium intake needs of full-term infants at calcium levels similar to those found in typical lactose-containing, cow's milk-based formulas.
Technical Abstract: Background: Calcium absorption is enhanced by the presence of lactose, but the quantitative significance of this effect in infant formulas is uncertain. It is also not known whether lactose affects zinc absorption. Objective: We measured the absorption of calcium and zinc from infant formulas by using a multitracer, stable-isotope technique. Design: Eighteen full-term infants (aged 8-12 wk at enrollment) were fed 2 partially hydrolyzed whey-protein-based formulas ad libitum for 2 wk per formula. The carbohydrate source was lactose in one formula and glucose polymers in the other (lactose-free). Infants were studied in a blinded crossover fashion after 2 wk of adaptation to each formula. Isotope absorption studies were conducted with a 4-tracer method in which 70Zn and 44Ca were provided orally and 67Zn and 46Ca intravenously. Zinc and calcium absorption was measured from the fractional excretion of the oral and intravenous isotopes in urine. Results: Fractional and total calcium absorption was significantly greater from the lactose-containing formula than from the lactose-free formula. For total calcium absorption, the mean difference between formulas was 10.3% (P = 0.002) and 60 mg/d (P = 0.006). For zinc, fractional absorption (32 ± 11%), total absorption, and intake did not differ significantly between the 2 formulas. Conclusions: The presence of lactose in a formula based on cow milk protein increases absorption of calcium but not of zinc. Absorption of calcium from a lactose-free infant formula is, however, adequate to meet the calcium needs of full-term infants when the formula's calcium content is similar to that of lactose containing, cow-milk-based infant formulas