Dialyzability of iron, zinc, and copper of different types of infant formulas marketed in Spain.

The bioavailability of trace elements in infant formulas is affected by different physiological and dietetic factors. In vitro methods based on element dialyzability have been proposed to estimate the bioavailability. Infant formulas of the same type but from different manufacturers can differ in the salt used for supplementation and in the contents of other components that can affect mineral bioavailability. The aim of our study is to estimate the dialyzability of iron, zinc, and copper of formulas marketed in Spain, in order to detect possible differences in formulas of the same type coming from different manufacturers. At the same time, the effects of the type of formula, the composition of the protein fraction, and the mineral content on the element dialyzability are also studied. Differences are found in the dialysis percentages of the elements studied in formulas of the same type but from different manufacturers. The formulas giving the highest dialysis percentages for the three considered elements are the hypoallergenic ones based on protein hydrolysates. No differences are observed in formulas having whey or casein as the main protein fraction. Significant correlations are obtained between the element contents and the dialyzability of the elements.