Fiber, a complex carbohydrate, is generally defined as the part of a plant that cannot be digested. Thus, it adds virtually no calories to the diet. There are two types of fiber, soluble and insoluble. Insoluble fiber promotes regular bowel movement and speeds up the passage of food through the body. Good sources of fiber include vegetables such as green beans and dark green leafy vegetables, fruit, whole-wheat products, nuts and seeds.

Soluble fiber helps lower total cholesterol and regulate blood sugar for people with diabetes. The quantity of fiber needed to produce this effect varies by food source. Food sources of soluble fiber include oat bran, dried beans and peas, nuts, flax seed, carrots, prunes and apples.

Dietary fiber is beneficial for many health conditions, such as diverticulitis, colon cancer and diabetes. Eating fiber-rich foods is the best way to improve intestinal health. The American Cancer Institute recommends 20 to 30 grams of dietary fiber each day. Check the food label on each product to determine the amount of fiber it provides. Be sure to add fiber to your diet slowly and increase your fluid intake to aid digestion.