Dietary phytate reduces magnesium bioavailability in growing rats

The aim of the present study was to evaluate the effect of dietary phytate on Mg bioavailability in rats. Male rats with an initial average weight of 60 g were fed ad libitum semisynthetic diets based on casein and corn starch containing 300 mg Mg/kg and increasing levels of sodium phytate (0, 4, 8, 12, 16, 20 g/kg) over 21 days. The addition of increasing levels of phytic acid to the diets resulted in a dose dependent decrease of the apparent magnesium absorption. Urinary magnesium declined in tendency with increasing levels of dietary phytate. Similarly to apparent Mg absorption and Mg balance, dietary phytate decreased whole body magnesium retention dose dependently. Higher intakes of phytic acid reduced plasma and femur Mg concentration and impaired body weight and feed efficiency. (C) 1998 Elsevier Science Inc.