& Joannie Dobbs Wednesday,
Fiber in diet can provide long-term health
You probably didn't realize January was both "Fiber Focus Month," and "Oatmeal Month." And even though dietary fiber is strictly speaking not an essential nutrient, the Food and Drug Administration allows oatmeal and other similar high-fiber foods to make food label claims that they may help reduce the risk of certain cancers and heart disease when part of a healthy diet.
You can live without fiber. Eskimos in Arctic regions and Masai tribes of East Africa survived on diets virtually devoid of fiber. In fact, it may seem surprising that something like fiber could have any effect on health. After all, by definition, it just passes right through the gastrointestinal tract and never enters the blood or any other part of the body.
Fiber is like many other so-called phytochemicals. We can survive without them, but including them in the diet can provide many long-term health benefits.
Fiber is found only in plant foods, with some minor exceptions, one being a compound called chitin that is found in the shells of crustaceans such as shrimp and crab. Some dietary supplements contain a processed form of chitin called chitosan.
Dietary fibers are classified as either insoluble or soluble in water. Both types are important in holding water in the intestinal tract. Insoluble fiber keeps things moving along, especially in the colon, whereas soluble fiber slows down the rate at which meal contents move from the stomach to the small intestine.
As a consequence, when a meal contains soluble fiber, absorption is slowed and chemicals such as sugar enter the blood more gradually and raise blood-sugar levels more slowly than a similar meal low in soluble fiber.
It is thought that repeatedly high blood-sugar levels may have adverse effects on health over time. A lifelong diet of foods high in soluble fiber may help decrease the risk of developing diabetes.
With respect to heart disease, it is not clear exactly how fiber works, but diets higher in soluble fiber do tend to lower blood cholesterol levels. Of course, this helps to reduce the risk of heart disease.
Both types of fiber may benefit colon health. Soluble fiber provides nutrients for beneficial intestinal bacteria and insoluble fiber helps keep toxic byproducts from building up in the intestines and colon. This may help reduce the risk of colon cancer and prevent the development of diverticulitis.
The American Dietetic Association recommends that adults consume between 24 and 30 grams of dietary fiber per day. This can be obtained by including commonly recommended amounts of fruits, vegetables, whole grains and beans in the diet.
Too much fiber can cause problems. Besides reducing the absorption of important minerals, if plenty of water is not consumed, fiber supplements such as wheat and oat bran can backfire and make stools very hard and difficult to eliminate.
To evaluate your total fiber intake (soluble and insoluble), you can get a rough estimate of the dietary fiber in common foods using some general numbers for half-cup servings. Fruits and vegetables average 1.5 grams total fiber, cooked refined grains 1.0 gram, whole grains 2.5 grams, and beans 3 to 5 grams. Reading the nutrition facts panels on food labels will help complete the tally.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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