Fiber is a type of carbohydrate found in plant foods. It's not digested or absorbed by the body. Fiber is often referred to as soluble or insoluble. This depends on whether it dissolves in water. Food sources include bran, whole grains, vegetables, fruits, and seaweed.
Soluble fiber can interfere with the absorption of dietary fat and cholesterol. This can help lower low-density lipoprotein (LDL or “bad”) cholesterol levels in the blood. It can also help control blood sugar after a meal. Insoluble fiber can speed up the movement of food through the large intestine and relieve constipation.
Studies suggest that fiber may help prevent colon cancer.