Fiber Roughs It Out

Last Editorial Review: 1/30/2005

Can fiber prevent colon cancer? Studies are mixed. But there's no doubt it's good for your heart.

WebMD Feature

Reviewed By Charlotte Grayson

White bread. Refined flour. Junk food. Each culprits, and together the prime suspects for causing the country's most heinous health ills. Health experts implored Americans to substitute multigrain pancakes for fluffy waffles and bran muffins for bagels. Fiber was the be-all and end-all. It was the lifeboat riding above the tide of colon cancer -- one of the most feared cancers of all.

Researchers dubbed fiber a "colonic broom." The long, stringy strands of whole wheat and other fiber-rich foods formed a meshwork that grabbed on to cancer-causing substances and hustled them out of the intestines. It made sense. Few physicians disputed the recommendations.

Then came the headlines that slowed the momentum. One study involving nearly 90,000 women showed that fiber wasn't the crown prince of nutrients, after all. Women who ate about 28 grams of fiber a day weren't any less likely to develop colon cancer than those who ate no more than 8.5 grams, according to research published in the January 21, 1999 issue of the New England Journal of Medicine.

Along came more studies, published in the May 3, 2003 issue of The Lancet. Only these two studies show that people who eat high fiber diets are 25% less likely to develop colon cancer.

No wonder the public is confused. But don't toss that high-fiber cereal yet. Hold off on buying that loaf of soft, white bread. Fiber does guard against many serious health problems, especially heart disease. The research evidence on that is clear. Indeed, one study published in the October 27, 1999 issue of the Journal of the American Medical Association, found that fiber-eating young adults had lower cholesterol levels, lower blood pressure, and were less likely to be overweight and develop diabetes.

Researchers say most of us should be eating twice as much fiber as we now consume. The average daily intake is only 12 grams, but we should eat at lease 25 grams of fiber.

That means packing your diet with fiber-rich foods. A small serving -- one cup -- of Raisin Bran yields 7 grams of fiber. A bowl of vegetarian chili at lunch could add to your daily total, with one cup of kidney beans providing more than 7 grams of fiber. Figure in some fruits and vegetables -- and perhaps a fiber supplement sprinkled into your juice -- and you're on your way to meeting your daily goal.

Food for the Heart

The reward for such efforts is a shield against heart disease, showed research published in the September 1999 issue of the American Journal of Clinical Nutrition. Studying the same group of women in the Harvard study, the researchers found that women who managed to eat at least 25 grams of fiber a day were 40% less likely to suffer a heart attack than were women who ate less than 9 grams.

Men get the same protection. In the Harvard Male Health Professionals study, researchers found that men who ate a high-fiber diet could cut their risk of suffering a heart attack by almost half, according to results published in the February 14, 1996 issue of the Journal of the American Medical Association.

How fiber works its magic still isn't clear, but scientists suspect that it coaxes the body to take more cholesterol out of the blood, preventing it from forming plaques in the arteries and causing heart disease.

Fiber also blocks the body from absorbing fat and cholesterol from food. In the April 1997 issue of the Journal of Nutrition, researchers reported that the more fiber volunteers ate, the more fat ended up in their stools.

Flushing Out the Pounds

Not only does fiber prevent absorption of fat, but it also helps you to feel satiated faster. As you fill up on high-fiber foods like grains, fruits, and vegetables, you'll have less room for high-fat and highly caloric low-fiber foods.

And fewer calories mean that eating fiber helps to maintain a healthy weight. Some researchers have calculated that if Americans doubled their intake of fiber, they could cut 100 calories from their diet a day, which could shave off 10 pounds of yearly weight gain.

Protection From Diabetes

There's good reason to think that fiber can protect against diabetes, too, based on results published in the February 12, 1997 Journal of the American Medical Association. In a study of more than 65,000 middle-aged women, scientists reported that women who consumed the most fiber were significantly less likely to develop diabetes than those who ate the least.

A Defense Against Diverticulitis

Fiber could even cut into the number of Americans -- about half of those over 60 -- who develop a painful condition called diverticulitis, which occurs when outpouchings in the intestinal wall become inflamed or infected. In results reported in the November 1994 issue of the American Journal of Clinical Nutrition, the risk for fiber-eating males of developing diverticulitis was about half that of men who didn't eat much fiber.

Convinced? Don't jump in too fast. Incorporate fiber into your diet gradually to prevent the gas and bloating that can occur if your body is unaccustomed to digesting fiber in large amounts. And drink at least 8 cups of water daily to keep the fiber moving through your system.

And while the jury is still out on fiber's ability to prevent other diseases such as breast cancer, the scientific evidence, on balance, backs fiber's disease-preventing potency. Fiber's not glamorous. Disguised in shiny red apples and the crispy sweetness of garden fresh carrots, this beleaguered, shunned, and sometimes unappreciated nutrient can be quite a treasure. But regardless of how you see it, fiber still reigns.

Medically updated July 15, 2003.

Originally published March 27, 2000.

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