Resistant starch lowers fecal concentrations of ammonia and phenols in humans

Abstract

We investigated the effect of resistant starch (RS) on markers of colonic protein metabolism. Eleven subjects participated in a randomized crossover study in which they consumed either high-RS (39 ± 3 g/d, χ̄ ± SEM) or low-RS (5 ± 0.4 g/d) diets for 3 wk. All other macronutrients were kept constant. During the high-RS diet daily excretion of fecal nitrogen increased from 1.84 ± 0.15 to 2.86 ± 0.42 g/d (P < 0.01) and excretion of fecal phenols fell from 9.2 ± 1.4 to 5.3 ± 0.8 mg/d/P < 0.01). Fecal concentrations of ammonia decreased from 397 ± 33 to 278 ± 49 μg/g (P < 0.01) and phenols decreased from 69 ± 8 to 39 ± 10 μg/g (P < 0.001). Daily output of urinary ammonia, urea, phenols, and total nitrogen did not change significantly, but pH decreased from 6.4 ± 0.1 to 6.2 ± 0.1 (P < 0.05) during the high-RS period. These results suggest that RS significantly attenuates the accumulation of potentially harmful byproducts of protein fermentation in the human colon.