Hydroxypropyl-modified potato starch increases fecal bile acid excretion in rats

The effects of hydroxypropyl potato starches (HPS) of three different degrees of substitution (DS) on concentration of plasma cholesterol, apparent digestibility of protein, fecal excretion of bile acids, fecal output and cecal pool of organic acids such as acetic, propionic, butyric, lactic and succinic acid were studied in rats in Experiment 1. In Experiment 2, the effects of hydroxypropyl distarch phosphate (HDP) of three different degrees of cross-linking (DC) on the same indexes were studied. Gelatinized potato starch that was not modified chemically (PS) was used as a control. Rats were fed a fiber-free, purified diet containing either HPS, HDP or PS (100 g/kg) for 21 d. In each experiment, fecal output was greater and fecal excretion of bile acids was higher in rats fed the HPS diets with higher DS and the HDP diets compared with control rats fed the PS diet. Apparent protein digestibility in rats fed the HPS diets with higher DS and the HDP diets with higher DC was lower than that in control rats fed the PS diet. The pool size of cecal organic acids was not affected by diet. In Experiment 1, apparent protein digestibility, fecal output and fecal bile acids excretion were significantly correlated with DS (r = -0.994, P = 0.0059; r = 0.976, P = 0.0236; and r = 0.899, P = 0.0077, respectively). The plasma cholesterol concentration was significantly lower in rats fed the HPS diets than in control rats fed the PS diet. The HPS diets resulted in higher proportions of propionic acid, lactic acid and succinic acid and a lower proportion of n-butyric acid than the PS diet. In Experiment 2, apparent protein digestibility was significantly correlated with DSP (r = 0.996, P = 0.0028), which was inversely related to DC. The HDP diets did not affect the plasma cholesterol concentration. The HDP diets resulted in higher proportions of acetic acid, lactic acid and succinic acid and a lower proportion of n-butyric acid than the PS diet. These results suggest that the physiological effects of chemically modified starches are affected by the type of modification.