Effect of traditional oriental soy products on iron absorption.

The effect of a variety of traditional oriental unfermented and fermented soy products on iron absorption was evaluated in 242 Indian women. When compared with a soy-flour meal containing an equal amount ofprotein, iron ab- sorption was found to be significantly improved with silken tofu, natto, tempeh, rice miso, barley miso, and soybean miso. This improvement could not be adequately explained except with reference to changes in the protein composition of the products. The protein fraction profiles ofthe soy products were obtained by size-exclusion high-performance liquid chroma- tography. An inverse relationship between food iron absorp- tion and the high-molecular-weight fraction ofthe soy products was demonstrated (r = 0.66, p 0.0 1 ). However, anomalous results obtained with three products (sufu, tempeh, and fully hydrolyzed isolated soy protein) did not make it possible to reach firm conclusions concerning the effect ofthe protein frac- tion ofsoy on iron bioavailability. Am J C/in Nutr l990;51: 873-80.