Fiber is a type of carbohydrate that the body can not digest or absorb in the blood stream. It is a polysaccharide which can be derived from all plant products like fruits, vegetables, cereals, and pulses. Fiber is not considered a nutrient because unlike other carbohydrates it does not add calories to a person's diet, nor does it give energy required by the body.
Fiber can be divided into three groups. Soluble Fiber forms a gel when mixed with a liquid. Like any other fiber it does not get digested but gets affected by intestinal bacteria during digestion. Insoluble Fiber does not dissolve in liquids. It passes through the intestine completely unaffected.
Resistant Fiber has been recently recognized and categorized as a third type of fiber. It provides the benefits of both types of fiber. It passes through the small intestine largely unaffected and is fermented in the large intestine.
Fiber does not provide calories to the body and hence can be helpful in controlling weight and preventing obesity. Fiber reduces fat absorption. It helps you to decrease your appetite by adding bulk to your diet and keeping you full for a longer period. It promotes rapid passage of food through the intestine. It also adds bulk and softness to stools preventing constipation, hemorrhoids, and irritable bowel syndrome.
It is found to reduce the total and LDL cholesterol levels, thereby reducing the risk of heart attacks. It reduces insulin requirement, resulting in controlled blood sugar levels. Studies have found a strong link between reduced risk of cancer and high fiber intake.
Fiber stimulates the production of short chain fatty acids in the intestines by balancing the pH, thus reducing the risk of colorectal cancer. In addition, foods rich in fiber are full of vitamins, minerals, and phytochemicals, all off which help in fighting various diseases.
The dietary requirements of fiber in men are 38 gm and 30 gm for those below 50 years of age and 51 or above, respectively. While women under 50 years require 25 gm of fiber, those that are 51 or above need 21 gm. Sources of soluble fiber are peas, soybeans, legumes, oats, rye, barley, fruits, vegetables, and psyllium. Sources of insoluble fiber are whole grain foods, wheat and corn, bran, nuts and seeds, potato skins, and flax seeds.
Animal sources of food including milk and milk products, meat, egg, fish have no fiber. The Dietary Guidelines and the Food Guide Pyramid recommend eating 2 to 4 servings of fruit, 3 to 5 servings of vegetables and 6 to 11 servings of whole grains and cereals each day to increase your fiber intake. Fiber should be gradually increased in one's diet. A sudden increase of fiber in diet can cause gas, diarrhea and bloating.
It is very important to drink plenty of water as fiber traps water in the intestines. Adding fiber to a child's diet or to an elderly patient's diet should be done with extreme care. Adding excess fiber to a child's diet may fill up the child too quickly and elderly patients may feel the added effect of fiber.