There are two types of dietary fiber -- soluble and insoluble. Both are important for health, digestion, and preventing diseases.
Soluble fiber retains water and turns to gel during digestion. This type of fiber dissolves in water to form a gel-like texture in the intestines. It also slows digestion. Soluble fiber is found in oat bran, nuts, seeds, beans, lentils, peas, some fruits and vegetables, barley and psyllium. Soluble fiber may help lower cholesterol and glucose levels.
Insoluble fiber adds bulk to the stool and appears to help food pass more quickly through the stomach and intestines. Insoluble fiber is found in foods such as whole wheat and whole grain products, vegetables, wheat bran, nuts, and brown rice.
Insoluble fiber does not dissolve in water while soluble fiber dissolves in water.
A high-fiber diet helps relieve and prevent constipation.