Fiber is plant material that is either poorly digestible or indigestible by enzymes within the gastrointestinal tract. When eaten, fiber tends to slow the rate of digestion and speed up the transit of food through the small intestine. The fiber itself passes through the small intestine relatively unchanged, resulting in increased stool volume. This is true for both soluble fiber, including apples, peas, beans, peas, oats, fruits and nuts, and for insoluble fiber such as cabbage, wheat and many root vegetables.
Foods rich in both insoluble and soluble fiber include bran, grains, corn, rice, fruits and many vegetables. Health care agencies recommend that adults eat approximately 25-30 grams of fiber per day, but the average American adult consumes only about half the recommended intake at present.
Dietary fiber may have significant health benefits when eaten in recommended amounts. It may help treat constipation by softening and enlarging stools. In addition, it may reduce the incidence of colorectal cancer – populations which eat a high fiber diet tend to have a low incidence of colorectal cancer – diverticular disease,diverticulitis and hemorrhoids. A high fiber diet may also help prevent or improve high cholesterol levels, heart disease and diabetes. Excess fiber in the diet may may result in bloating, excess gas and diarrhea or interfere with the absorption of some minerals.