To Your Health

Q. I've been hearing that fiber in the diet is not as important as we used to think. Is it really important, and if so what does it do?

A. For 30 years there has been debate over the value of dietary fiber and how much is enough. The newest rumor that fiber has lost its prominence in cancer prevention probably started about a year ago when an article in the prestigious New England Journal of Medicine reported that fiber supplements failed to stop the return of pre-cancerous colon growths in people with a history of developing these. Since this was a classic "double-blind" study it carries a lot of weight in the scientific community.

However, the study is open to criticism. One point is the question of whether a fiber supplement can be disguised sufficiently to actually have a double-blind study. By definition, in a double-blind study the participants do not know whether they are getting the fiber supplement. Fiber supplements are notoriously unsavory, and compliance with supplement use has been questioned. A second concern is the relatively short time frame of three years, which simply may not have been enough time for the difference in fiber intake, about 11 grams per day, to make a significant difference.

Dietary fiber content of a food is not easily judged. About the best that can be said is that vegetables and fruits supply about 2 grams of fiber per serving and beans and whole grains about 4 grams per serving. Meat, eggs, and milk supply virtually zero fiber.

While the role of fiber in colon cancer is still being discussed, even the rather staid American Diabetes Association recommends that diabetics aim for 40 grams of fiber per day, at least 1/3 of that in the form of soluble fiber, the sort that usually comes from vegetables and fruits. This amount is two to four times the American average intake and is difficult to manage without a fiber supplement. Six servings of vegetables and fruits plus five servings of whole-grain products would provide over 30 grams, but some people would become overweight if they added on that many calories (about 800) to their protein foods.

Food is certainly the best way to increase fiber, but supplements are available. With minor changes in fiber from food sources and a fiber supplement, a 10-12 gram/day increase in fiber intake is quite feasible. A newly available fiber, inulin, is tasty and easily mixes with a food or beverage. A heaping teaspoon of this or any of several other fiber powders before each meal would provide about 8 grams of fiber per day.

In the early summer of 2001, results of an eight-year study involving over half a million Europeans indicated that people with the lowest incidence of colon cancer (not the pre-cancerous growths mentioned above) ate more fiber than average. Europeans and Americans tend to have similar (and inadequate) dietary fiber intake and the message from this study seems clear: If you want to reduce your risk of colon cancer as well as diabetes, increase your intake of vegetables and whole grains or choose a fiber supplement.

Is there a down side to fiber? Yes, but nothing that cannot be overcome. High fiber intake hinders the absorption of minerals, calcium in particular, but this can be remedied with mineral supplements. Increased fiber intake will often temporarily increase intestinal gas, so a slow start and gradual increase over six weeks is more comfortable. If you are taking a cholesterol-lowering drug, consult your physician before using a fiber supplement. For the most part, high-fiber foods are nothing but good, generous in other nutrients (folic acid, for instance) that also have anti-cancer properties.

There is consensus among nutritionists that low-fiber diets are part of the cause for the increases in "diseases of affluence" in developing countries (cancer, heart disease, diabetes, etc). Even before the debate is settled you will likely live longer and happier if you find high-fiber foods that you can enjoy.