Resistant starch improves mineral assimilation in rats adapted to a wheat bran diet

The effects of a natural source of phytic acid (PA) such as wheat bran (WB), in the presence or in the absence of resistant starch (RS) on the assimilation of minerals (Ca, Mg, P) and trace elements (Fe, Mn, Zn, Cu) were investigated in rats adapted to semipurified diets. The diets provided either 73 g/100 g digestible wheat starch (DS) alone, or 53 g/100 g DS plus 20 g/100 g raw potato starch (RS) and either 0 or 20 g/100 g WB. Mineral content of all diets was adjusted before the beginning of the experiment. RS diets resulted in enlargements of the cecum together with an accumulation of short-chain fatty acids. As a result of the hypertrophy of the cecal wall, acidification of luminal pH and an elevated concentration of soluble minerals, the cecal absorption of Ca, Mg, and P was 3-5-fold higher in the RS groups than in the DS groups. Mineral apparent retention was significantly enhanced by RS ingestion (Ca, +39%; P, +30%; Mg, +32%; Zn, +47%; Fe, +27%; Mn, +5% and Cu, +37%). WB ingestion altered significantly P solubility and its cecal absorption. Thus, WB exerted a significant effect on P and trace elements balances (P, -29%; Zn, -60%; Fe, -26%; Mn, -22% and Cu, -47%). Nevertheless, with WB diets, the disappearance of phytic acid was 2-fold higher in rats fed the RS than those fed the DS. Thus, the addition of RS into WB diet allows a greater mineral absorption by increasing the organic acids production and the breakdown of PA in the large intestine. (C) 1999 Elsevier Science Inc.