Some foods contain fiber, which is a tough complex carbohydrate. Fiber may be
Partly soluble: It dissolves in water, and the body may be able to digest some of it.
Insoluble: It does not dissolve in water, and the body cannot digest it.
Eating too much insoluble fiber can interfere with absorption of certain vitamins and minerals.
Authorities generally recommend that about 30 grams of fiber be consumed daily. In the United States, the average amount of fiber consumed daily is about 12 grams because people tend to eat products made with highly refined wheat flour and do not eat many fruits and vegetables. An average serving of fruit, a vegetable, or cereal contains 2 to 4 grams of fiber. Meat and dairy foods do not contain fiber.