In vitro interactions between calcium, zinc, copper and iron in milk- and soy-based infant formulas / Interacciones in vitro entre calcio, cinc, cobre e hierro en formulas de base láctea y de soja para lactantes

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Abstract
Interactions among calcium, zinc, copper and iron in milk- and soy-based infant formulas were as sessed in order to evaluate the influence of supplementation with one trace element on the bioavailability of the others. The criterion used to estimate the bioavailability is the percentage of dialysis, estimated by applying an in vitro method. Infant formulas were supplemented with CaCl2, ZnO, CuCO3 Cu(OH) 22H2O and FeSO4 7H2O at two levels (maximum (+) and minimum (-) allowed by the European Union). A factorial design at two levels with three factors (Zn, Cu and Fe addition) was carried out. The main effects and the second-order interactions of the studied factors on the bioavailability of a given element were estimated. The results obtained for milk-based formulas clearly indicated the negative influence of iron at the high addition level (+) on the dialysis percentage of calcium, and of zinc at the high addition level (+) on its own dialysis percentage, whereas in the same type of formulas, the addition of zinc had a positive effect on the copper dialysis percentage. In soy- based formulas a negative effect of added copper (+) on its own dialysis percentage was observed. The most important second order interaction found to be significant was the negative effect of (zinc x iron) on copper dialysis in milk-based formulas.