Zinc bioavailability and infant formulas

Review: Effect of Some Components of Milk- and Soy-Based Infant Formulas on Mineral Bioavailability

“…Phytates are components of soy-based infant formula and, in general, have a negative effect on mineral, and especially zinc, absorption. This effect has been observed in human infants (Golden and Golden, 1981;Craig et al, 1984) and adults (Sandström et al, 1983;Lönnerdal et al, 1984), in suckling rats (Lönnerdal et al, 1994) and in in vitro assays of dialyzability (Shen et al, 1994;García et al, 1998;Jovaní et al, 2000b). It has been suggested that the dephytinization of infant formula has a greater enhancer effect on zinc bioavailability than an increase in the element content.…”

“…There is no conclusive evidence of a possible negative influence of phytate on copper absorption in humans (Fairweather-Tait and Hurrell, 1996), which might be because unlike phytate-zinc complexes, which precipitate at the pH of gastrointestinal tract, phytate-copper complexes are soluble in the intestine (Lönnerdal, 1996). As a matter of fact, serum copper contents, which are indicators of the nutritional state of the element, have not been found to vary depending on whether the infant formula is milk-or soy-based (Craig et al, 1984). Milk-(15.2-24.9%) and soy-based infant formulas (15.1-16.7%) have similar copper dialysis percentages (García et al, 1998).…”

“…In contrast, the negative effect of iron on zinc absorption can be a cause of concern for pediatricians, legislators and infant formula manufacturers, because iron supplementation of infant formulas is a common practice (Whittaker, 1998). As mentioned above, a high iron/zinc ratio can have a negative effect on zinc absorption in adults (Lönnerdal et al, 1984) and infants (Craig et al, 1984), but no effect of iron was observed even when the molar iron/zinc ratio was 5.4, which is higher than the usual in iron-supplemented infant formulas (2.8-4.0) (Haschke et al, 1986). Polberger et al (1996) found that the higher level of iron fortification (12 mg/L) in infant formulas did not significantly affect zinc retention in suckling rhesus monkeys.…”