In Vitro Estimation of Iron Availability in Meals Containing Soy Products

Effects on relative nonheme iron availability of soy protein products incorporated into meals were evaluated. An in vitro method was used to estimate nonheme iron availability. Incorporation of soy isolate into a semisynthetic meal reduced estimated iron availability (dialyzable iron) compared to an egg white control, but this effect was reversed by baking the soy isolate. Ascorbic acid was not as effective in increasing estimated iron availability in soy-containing meals as in an egg white control meal. When 34 individual soy products were substituted for egg white in a semisynthetic meal, iron availability ranged from 3.23 to 0.00% dialyzable iron. Iron availability appears to be inversely related to the protein content of the soy products. Soy isolates, as a group, had lower relative iron availability than the group of soy flours evaluated. The amount of soy product protein incorporated into a standard meal was negatively correlated with relative iron availability. The majority of meals containing soy products had lower estimated iron availabilities than meals that did not contain soy. iron iron availability in vitro iron absorption soy protein