Effect of resistant starch on fecal bulk and fermentation-dependent events in humans

This study investigated the effect of two diets, which differed in resistant starch (RS) concentration, on fecal bulk and fermentation-dependent events in 11 humans. Amounts of RS consumed were 5.0 ± 0.4 and 39.0 ± 3.0 g/d (x̄ ± SEM) for the low- and high-RS diets, respectively. The two diets were fed for 3 wk each in a randomized crossover design. Fecal collections were made in the third week of each study period. The high-RS diet produced an increase (P < 0.01) in total fecal output (from 138 ± 22 to 197 ± 37 g/d) and lowered fecal pH (6.9 ± 0.1 to 6.3 ± 0.1). There were significant increases (P < 0.05) in the fecal concentrations and daily excretion of butyrate (+38% and +100%, respectively) and acetate (+26% and +72%, respectively) during the high-RS period. The fecal excretion (g/d) of nonstarch polysaccharides (NSP) also rose by 50% during the high-RS diet, suggesting that the presence of starch in the colon may affect the fermentation of NSP. Subjects reported an increase in flatulence and easier defecation. These results demonstrate that RS has a significant impact on putative markers of colonic health in humans.