Some foods contain fiber, which is a tough complex carbohydrate. Fiber may be
Partly soluble: It dissolves in water, and the body may be able to digest some of it.
Insoluble: It does not dissolve in water, and the body cannot digest it.
Fiber in the diet helps mainly by adding bulk to the contents of the intestines. This helps make stool easier to pass and minimizes constipation Constipation in Adults Constipation is difficult or infrequent bowel movements, hard stool, or a feeling that the rectum is not totally empty after a bowel movement (incomplete evacuation). (See also Constipation... read more . Fiber also may provide satiety (the feeling of fullness and relief of hunger). However, eating too much insoluble fiber can make you feel bloated and also interfere with absorption of certain vitamins and minerals.
Authorities generally recommend that about 30 grams of fiber be consumed daily. In the United States, the average amount of fiber consumed daily is about 12 grams because people tend to eat products made with highly refined wheat flour and do not eat many fruits and vegetables. An average serving of fruit, a vegetable, or cereal contains 2 to 4 grams of fiber. Meat and dairy foods do not contain fiber.
Comparing Soluble and Insoluble Fiber
Type of Fiber
Apples (mainly in the flesh of the apple)
Pectin (from fruit)
Helps moderate the changes in blood sugar and insulin levels that occur after eating a meal
Helps reduce cholesterol levels
May reduce the risk of atherosclerosis Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more (including coronary artery disease Overview of Coronary Artery Disease (CAD) Coronary artery disease is a condition in which the blood supply to the heart muscle is partially or completely blocked. The heart muscle needs a constant supply of oxygen-rich blood. The coronary... read more )
Apples (mainly in the skin of the apple)
Many vegetables, including cabbage, root vegetables, and zucchini
Whole grains and whole-grain breads and pastas
Provides bulk to feces and thus helps food move through the digestive tract, preventing constipation
Helps eliminate cancer-causing substances produced by the bacteria in the large intestine
Reduces pressure in the intestine, helping prevent diverticular disease Definition of Diverticular Disease Diverticular disease is characterized by small, balloon-like sacs (diverticula) protruding through the layers of particular structures in the gastrointestinal tract (digestive tract). A single... read more
Makes people feel less hungry because it adds bulk to the diet, makes people chew more slowly, and keeps food in the stomach longer—and is thus helpful in losing weight