Effect of reducing the phytate content of infant cereals by using endogenous phytase on zinc and iron absorption in rat pups

Cereal is one of the most common weaning foods in both industrialized and less developed countries. Unfortunately, cereals contain relatively high concentrations of phytic acid, which is known to have an inhibitory effect on Zn and Fe absorption. Attempts have been made to reduce the phytate content by industrial processes, including precipitation methods, treatment with added phytase and fermentation. In this study, we optimized the process conditions for allowing endogenous phytase to reduce the phytate concentration of infant cereals, and evaluated the effects in a suckling rat pup model. Cereals and gruels (cereal+milk) with native and reduced phytate levels, milk formula and breast milk were studied. Diets were labelled with ⁶⁵Zn or ⁵⁹Fe and intubated to fasted pups(n=8/group). Pups were killed 4 h post-intubation, organs dissected and counted in a gamma counter. Zn absorption from untreated cereals varied between 42-68%. Reducing the phytate content increased Zn absorption from 47 to 75% for cereals (with fruit), from 63 to 86% for gruel and from 68 to 85% for cereal/milk as compared to milk formula (93%) and breast milk (95%). Fe absorption from untreated cereals was higher than Zn absorption and the effects of reducing phytate were less pronounced, although it increased from 70 to 90% for cereals. The results show that endogenous phytase can have positive effects on Zn and Fe absorption.