In vitro availability of zinc from infant foods with increasing phytic acid contents

An in vitro method was used to determine the availability of Zn from infant foods containing increasing amounts of phytate, and to quantify the effect of the phytate:Zn molar ratio on the availability. During the in vitro ass ay, digestive conditions of infants, younger and older than 4 months of age , were carefully simulated since the solubility of phytate-Zn complexes dur ing digestion is pH dependent. Availability was measured with a continuous flow dialysis in vitro procedure with previous intralumen digestive stage. Zn concentrations were determined with flame atomic absorption spectrometry . Phytic acid content was measured with HPLC. Adding phytate to infant form ula lowered Zn availability to 2.84 (sd 0.17) % when the phytate:Zn molar r atio increased to 2.2 (P<0.05), as compared with cows' milk-based formula ( 6.65 (sd 0.55) %). Availability from vegetables (23.83 (sd 2.17) %) signifi cantly decreased (P<0.05) at a ratio > 7.9 (15.12 (sd 1.63) %). Zn availabi lity from soyabean-based formula (2.26 (sd 0.36) %) was lower (P<0.05) comp ared with cows' milk-based formula (6.65 (sd 0.55) %). Availability between soyabean- and cows' milk-based formula was similar (P>0.05) when a phytate :Zn ratio of 2.2 (2.84 (sd 0.17) %) was obtained in the cows' milk formula. The negative effect of phytic acid on Zn availability was dependent on the type of the food and the phytate content, and should be considered when us ing soyabean-based formulas during early infancy.