What is the function of fiber in the body?

According to the Mayo Clinic, fiber prevents and relieves constipation, helps to maintain a healthy weight and lowers the risk of diabetes and heart disease. There are two types of fiber: soluble fiber and insoluble fiber.

Soluble fiber dissolves in water and helps lower cholesterol and glucose levels, states the Mayo Clinic. Soluble fiber is found in oats, beans, citrus fruits and apples. Insoluble fiber does not dissolve and promotes proper digestion and bowel movements. It is found in whole-wheat flour, nuts, cauliflower, green beans and potatoes. The Mayo Clinic explains that men under 50 need to consume 38 grams of fiber per day and women of the same age group need 25 grams.