Soluble fiber disolves in water soaking up fluid in the stomach and small intestine.  Soluble fiber slows down digestion in the stomach and small intestine.  This helps to slow down the conversion of other carbohydrates into glucose, thus stabilizing blood glucose levels.  Soluble fiber may also increase the uptake of minerals and other nutrients in food.   Soluble fiber appears to reduce blood cholesterol levels.  This is because the fiber binds with bile acids and cholesterol in the digestive tract, preventing them from being absorbed by the body.  Soluble fiber may also have cancer benefits.  It also absorbs fats and cholesterol.

Insoluble fiber moves through the body cleaning up substances that have been eaten that may be harmful.  Insoluble fiber improves the health of the intestinal tract by increasing stool volume and stimulating normal bowel contractions (peristalsis) thus reducing transit time through the colon.  By accelerating the speed of food through the intestinal tract, insoluble fiber may help prevent digestive disorders such as constipation or diverticulosis (infection caused by food getting stuck in small pouches in the wall of the colon). It may also reduce the absorption of salt (thus reducing the risk of raised blood pressure) and toxins.