If the propoion of the dietary fiber/roughage is high in a diet, it will:

Dietary fiber contains pectin, cellulose & hemicelluloses, lignin (non-carbohydrate). It has water-holding propeies--> it increases bulk in stomach. Large volume, together with higher viscosity, causes slow down of gastric emptying. It also slows down the motility of small intestine. Thus, transit time of the food (with high fiber) will increase in small intestine. Option B is incorrect. As it increases the volume and viscosity of the colonic contents, motility of the colon will increase. Hence, stool transit time will decrease in the colon. Option A is correct. It decreases the glycemic response due to slow gastric emptying Option C is incorrect. Dietary fiber has a bile salt-binding effect which increases fecal excretion of bile salts, and reduces bile salts available for entero-hepatic circulation - Option D is incorrect.