Why is fiber important to the body?

Dietary fiber (also spelled "fibre" and also called "roughage") helps you maintain an ideal weight by absorbing water, slowing the emptying of your stomach, and adding volume to food so that you feel full longer. Foods high in fiber often require more chewing, so it takes more time to eat, and you can't eat a large number of calories in a short amount of time. It helps to prevent Diabetes by slowing the entrance of glucose into the bloodstream, reducing glucose and insulin spikes after meals. Fiber helps prevent deaths from coronary Heart disease. Fermentation of fiber and resistant starch by bacteria in the large intestine helps to prevent colorectal cancers.

Insoluble fiber, found in the cell walls of plants, makes stools softer and bulkier. It also helps move food along the digestive system by peristalsis (waves of muscle contractions), preventing constipation. Insoluble fiber also prevents diverticulosis, a painful inflammation of the intestinal wall.

Soluble fiber, found inside plant cells, increases the viscosity of food, which slows the movement of food through the intestines, preventing diarrhea. Soluble fiber also lowers LDL ("bad") cholesterol in the bloodstream. One of the fatty acids produced by the fermentation of soluble fiber in the large intestines may also inhibit the amount of cholesterol produced by the liver.

Dietary fiber is found only in plant foods: fruits, vegetables, nuts, and grains. Meat, milk, and eggs do not contain fiber. Canned and frozen fruits and vegetables contain just as much fiber as raw ones. Drying and crushing, however, destroy the water-holding qualities of fiber. Removing seeds, peels, or hulls also reduces fiber content. For example, whole tomatoes have more fiber than peeled tomatoes, which have more than Tomato Juice. Likewise, whole wheat bread contains more fiber than white bread.