As it goes through your gastrointestinal system, it absorbs water and swells. Any food that is undigested is excreted in the stool, as are other waste products. Research has studied the relationship between high fiber diets and lowering the incidence of colon cancer and diverticulosis. Also, researchers are looking at high fiber diets for lowering the cholesterol level in the blood and managing diabetes. Insoluble fiber is effective at increasing stool size and bulk and helps reduce constipation and hemorrhoids.
Insoluble fiber includes wheat bran, whole cereal grains and vegetables.
Researchers have suggested that insoluble fibers may reduce colon cancer and diverticulosis. On the other hand, soluble fiber forms a gelatin-like substance in the intestines and increases the water content in stool. Researchers have suggested that soluble fiber decreases blood cholesterol and results in a lower blood sugar after meals for diabetics. Perhaps you have seen all the oat bran advertising in the media and your grocery store. So yes, grandmother was right when she said an apple a day is good for you, if you eat the peel.