Influence of the sulphydryl content of animal proteins on in vitro bioavailability of non-haem iron

Meat is a known enhancer of non-haem iron bioavailability from foods. The exact mechanism by which this enhancement occurs remains unknown. This present study was designed to identify the 'meat factor'. The ability of different animal proteins to reduce non-haem Fe(III) to Fe(II) during an in vitro digestion was determined. The role of the -SH content of the proteins was also evaluated. When compared to egg albumin, meats from different species significantly enhanced dialysable ionic iron, D-(Fe(II) + Fe(III)), and dialysable Fe(II), D-Fe(II), (p < 0.05). In contrast, whey protein was inhibitory. Statistically significant linear correlations were established between the -SH content of the systems and their ability to reduce Fe(III) (r(2) 0.451, p < 0.02) and dialyse the Fe(II) formed (r(2) 0.524, p < 0.01). Incorporation of the -SH blocking agent, N-ethylmaleimide, significantly inhibited Fe(III) reduction and Fe(II) dialysability in a dose-related manner. These results suggest that the -SH content of animal proteins plays an important role in enhancing non-haem iron bioavailability and hence, may be related to the 'meat factor'. (C) 1998 Elsevier Science Ltd. All rights reserved.