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 assimil ation of minerals (Ca, Mg, P) and trace elements (Fe, Mn, Zn, Cu) were inve stigated in rats adapted to semipurified diets. The diets provided either 7 3 g/100 g digestible wheat starch (DS) alone, or 53 g/100 g DS plus 20 g/10 0 g raw potato starch (RS) and either 0 or 20 g/100 g WB. Mineral content o f all diets was adjusted before the beginning of the experiment. RS diets r esulted in enlargements of the cecum together with an accumulation of short -chain fatty acids. As a result of the hypertrophy of the cecal wall, acidi fication of luminal pH and an elevated concentration of soluble minerals, t he cecal absorption of Ca, Mg, and P was 3-5-fold higher in the RS groups t han 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 ceca l absorption. Thus, WB exerted a significant effect on P and trace elements balances (P, -29%; Zn, -60%; Fe, -26%; Mn, -22% and Cu, -47%). Nevertheles s, with WB diets, the disappearance of phytic acid was 2-fold higher in rat s fed the RS than those fed the DS. Thus, the addition of RS into WB diet a llows a greater mineral absorption by increasing the organic acids producti on and the breakdown of PA in the large intestine. (C) 1999 Elsevier Scienc e Inc.