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Unraveling fiber.

proteins, fats, carbohydrates, vitamins and minerals--these are the basic materials from which our bodies build muscle, repair tissue and draw energy. But what of fiber, the mysterious substance we hear about periodically as a vital element of good health? Is it a nutrient? Where do we find it and what exactly is its role?

Why is fiber listed separately?

Because fiber is not absorbed into the bloodstream, it has had a hard time achieving nutrient status. Yet, fiber certainly promotes tissue maintenance and repair; one of its products, butyrate, is the primary energy source for colon cells. In 2002, the Dietary Reference Intake Committee on Macronutrients established a daily value for fiber, 14 g/1000 kcals. The chair of that panel was Joanne R. Lupton, PhD, Regents Professor, University Faculty Fellow and William W. Allen Endowed Chair in Human Nutrition at Texas A&M University. In 2001, she also served as chair of the Institute of Medicine's Panel on the Definition of Dietary Fiber. In Dr. Lupton's opinion, fiber is clearly a nutrient. She likens its status to the recent push to include the healthful compounds in red wine or cruciferous vegetables as nutrients.

Regardless of its status, clinicians agree that fiber contains a surprisingly versatile array of beneficial health properties:

Fighting cancer and heart disease

* The body's inability to entirely digest fiber accounts for fiber's role as a source of "bulk," which helps the intestines move waste along, an asset to the war on cancer-causing bacteria in the digestive tract.

* Fiber helps produce and repair colon cells.

* Fiber binds fats in the intestine and helps lower the body's cholesterol level.

Fiber and weight loss

Fiber promotes weight loss in several ways:

* The bulk consumed when fiber is eaten provides a full feeling faster.

* Fiber slows gastric emptying, also providing a full feeling longer. By keeping the food out of the bloodstream for a longer period, fiber moderates sharp changes in blood sugar after meals. In addition to this, fiber-rich foods themselves tend to have a low glycemic index (or GI, a measure of how readily the carbohydrate in a given food converts to simple sugar). This, too, is tied to the satiety you feel after eating a meal high in fiber.

* Since fiber isn't absorbed into the blood, you can eat more of it, gram for gram, than other foods, without subjecting yourself to excessive calories. In contrast, high-fat foods occupy much less room in the stomach while simultaneously offering far more calories per gram.

* Fiber forces more chewing, which slows down eating, helping you realize you're full before you've overeaten.

* Because they are not animal-based, fiber-rich foods almost never contain cholesterol or saturated fat.

Whole vs. wheat

Whole grains are not the same as fiber, but fiber certainly is an important component of them. These nutritious grains, then, are an excellent guide to finding fiber on the supermarket shelves. When shopping, keep the following points in mind:

* The operative word--in the first or second ingredient listed--is "whole," not "wheat." You want unrefined grains, which haven't had the fiberous bran separated from the starchy endosperm during the milling process. That is, you want the whole grain. Don't be fooled by terms like "stone-ground," "multigrain," "cracked wheat" or "organic."

* In addition to whole grain breads, other fiber-rich foods include citrus fruit, strawberries, beans and oatmeal. Foods with two or more grams per serving are considered fiber-rich. A serving of fruit, vegetables or whole-grain cereal contains between two and four grams of fiber.

* The trouble with white rice and potatoes is that they have both a high GI and a high glycemic load (see sidebox on p. 2), without the fiber. A food like shredded wheat has a fairly high GI, but you're at least benefiting from consuming the whole grain.

(Dietary Reference Intakes: Proposed Definition of Dietary Fiber, 2001, The National Academies Press, Washington, DC, 74 pp., www.nap.edu/books/0309075645/html/; Harvard Women's Health Watch, 2003, Vol. 11, No. 4, p. 6; personal corresp. Joanne Slavin, PhD, RD, Professor, Department of Food Science and Nutrition, University of Minnesota; personal corresp. Joanne R. Lupton, PhD, Regents Professor, University Faculty Fellow and William W. Allen Endowed Chair in Human Nutrition at Texas A&M University; Merck Manual of Medical Information, 2nd ed., 2003, pp. 880-887, 923-924)
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Title Annotation:Foods you Choose
Publication:Running & FitNews
Geographic Code:1USA
Date:May 1, 2004
Words:716
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