Health Encyclopedia

Fiber

Definition

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

Alternative Names

Diet - fiber; Roughage; Bulk

Function

Dietary fiber adds bulk to your diet. Because it makes you feel full faster, it can be helpful in controlling weight. Fiber aids digestion, helps prevent constipation, and is 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. This usually goes away once 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 of minerals such as iron, zinc, magnesium, and calcium. However, this effect usually does not cause too much concern because high-fiber foods are typically 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

Marlett JA, McBurney MI, Slavin JL. 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.

Review Date:8/6/2007
Reviewed By:Cynthia Dennison Haines, MD, family physician specializing in nutrition, fitness, and preventive health, St. John's Mercy Medical Center, St. Louis, MO, and Assistant Clinical Professor, St. Louis University's School of Medicine, Department of Community and Family Medicine.

ADAM Quality A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.