Balancing the facts on fiber
The body requires essential nutrients like vitamins and minerals. We can't live long if even one is missing. But, there is more to good nutrition than essential nutrients.
Foods contain many compounds that enhance health, but we can live without them.
Many of these components are called zoochemicals when present in animal foods and phytochemicals if found in plants. Dietary fiber is a phytochemical that is listed on food labels because it benefits health.
Question: What is dietary fiber?
Answer: Simply put, fiber refers to the nondigestible components in plant foods or similar compounds added to foods.
Some constituents of fiber are partially digested in the lower intestine by microorganisms. We can absorb some of the microbial byproducts generated from fiber and indirectly obtain about two calories per gram of fiber -- this is half the calories we get from starch and sugar.
Q: What are the benefits of fiber?
A: Fiber enhances intestinal function and helps to prevent constipation. Some types of fiber tend to lower blood cholesterol and slow down the rise in blood sugar after a meal. The combined effects of fiber can even help to reduce the risk of coronary heart disease, diabetes and possibly colon cancer.
An adequate supply of fiber also promotes a balanced "intestinal ecology" of beneficial microorganisms.
Q: What foods provide fiber?
A: Beans and other legumes like peas and lentils qualify as "all-star" fiber foods, with an 8-ounce cup providing 8 to 15 grams. Whole grain foods, vegetables, fruits and nuts are the other key sources of fiber.
Q: How much fiber do we need?
A: The Institute of Medicine recommends that after the age of 1 year, our diets contain about 14 grams of fiber for every 1,000 calories we consume. So, someone who consumes 2,000 calories a day should get 25 to 30 grams of fiber as part of their diet.
Q: Can you get too much fiber?
A: Of course! Everything has limits. Those health messages that say, "Eat more fruits, vegetables and whole grains" assume that you are not eating much of them. Perhaps the message should be "eat enough."
Too much fiber can reduce the ability to absorb essential minerals like iron, calcium and zinc. Also, excessively high fiber intake can even cause constipation when someone does not drink adequate fluids.
As always, good health is a matter of balance rather than extremes.
, 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 Services and prepares the nutritional analyses marked with an asterisk in this section. See also: Health Events