Soluble fibre helps to slow digestion and regulate blood sugar, while insoluble fiber helps move waste through the intestines, encouraging regular bowel movements. Soluble fiber is found in foods such as avocado, sweet potato and tofu, while insoluble fiber is found in wheat bran, most grains and most beans.
Both types of fiber are non-digestible elements found in plant products such as grains, legumes and vegetables. The majority of foods that contain fiber contain both soluble and insoluble fiber, though some foods may be better sources of one or the other. Soluble fiber gets its name because it tends to dissolve in water and form a gel-like substance, while insoluble fiber does not dissolve and passes through the digestive system mostly unchanged.
Soluble fiber binds to fatty acids in food. It also regulates blood cholesterol and promotes slower, more regulated digestion of sugars. Insoluble fiber keeps waste moving through the intestines so that toxic waste does not build up. It also regulates the pH balance in the intestines.
Foods rich in soluble fiber include oats and oat bran, blueberries, nuts and apples. Foods high in insoluble fiber include whole wheat bread, brown rice and the skins and peels of fruits and vegetables.