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Fiber

Definition

Fiber is a substance foundin plants. Dietary fiber -- the kind you eat -- is found in fruits, vegetables, andgrains. It is an important part of a healthy diet.

Alternative Names

Function

Dietary fiber adds bulk to your diet. Because itmakesyou feel full faster, it can be helpful in controlling weight. Fiberaids digestion, helps prevent constipation, andis sometimes used for the treatment of diverticulosis, diabetes, and heart disease.

Food Sources

There are two forms of fiber: soluble and insoluble.

Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. Soluble fiber has been scientifically proven to lower cholesterol, which can help prevent heart disease.

Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It appears to speed the passage of foods through the stomach and intestines and adds bulk to the stool.

Side Effects

Eating a large amount of fiber in a short period of time can cause intestinal gas (flatulence ), bloating, and abdominal cramps. Thisusually goes awayonce the natural bacteria in the digestive system get used to the increase in fiber in the diet. Adding fiber gradually to the diet, instead of all at one time, can help reduce gas or diarrhea.

Too much fiber may interfere with the absorption ofmineralssuch asiron, zinc, magnesium, and calcium. However, this effect usually does not cause too much concern because high-fiber foods aretypically rich in minerals.

Recommendations

The average American now eats 10 - 15 grams of fiber per day. The recommendation for older children, adolescents and adults is 20 - 35 grams per day. Younger children will not be able to eat enough calories to achieve this, but introducing whole grains, fresh fruits and other high fiber foods is suggested.

To ensure adequate fiber intake, eat a variety of foods, including more fruits, vegetables, whole grains, cereals, and dried beans and peas. Add fiber gradually over a period of a few weeks to avoid abdominal discomfort. Water aids the passage of fiber through the digestive system. Drink plenty of fluids (approximately 8 glasses of water or noncaloric fluid a day).

Peeling can reduce the amount of fiber in fruits and vegetables. Eating fiber-containing food is beneficial whether it is cooked or raw.

References

MarlettJA, McBurneyMI, SlavinJL. Position of the American Dietetic Association: Health Implications of Dietary Fiber. J Am Diet Assoc. 2002;102(7): 993-1000.

Howarth NC, Huang TT, Roberts SB, McCrory MA. Dietary Fiber and Fat Are Associated with Excess Weight in Young and Middle-Aged US Adults. J Am Diet Assoc. 2005;105(9):1365-72.

Seki T, Nagase R, Torimitsu M, et al. Insoluble fiber is a major constituent responsible for lowering the post-prandial blood glucose concentration in the pre-germinated brown rice. Biol PharmBull. 2005 Aug;28(8):1539-41.

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