Increasing starch intake in the human diet increases fecal bulking.

Fecal bulking occurs through water holding by dietary residue as well as by enhanced bacterial mass as a result of bacterial utilization of dietary fiber. In this study, increasing the energy intake of human subjects by supplementing the carbohydrate content of the diet with corn starch increased fecal weights and fecal nitrogen content. This indicates that the carbohydrate content, more specifically the starch content, of the diet influences fecal bulking by possibly increasing available substrates for colonic bacterial proliferation which are dependent largely on undigested fiber in the colon. This may explain why high fecal weights occur in the tropics on comparable intakes of dietary fiber but on high starch intakes.