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Correction to This Article
Dec. 15 Food column on fiber omitted the first name of author and registered dietitian Leslie J. Bonci.
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Rough It

Heart Disease Prevention Fiber can help prevent heart disease in a variety of ways:

• Lower levels of insulin associated with a high-fiber diet can reduce the risk of heart disease and heart attacks.

_____Supplemental Evidence_____
Fiber Facts

• Viscous (or soluble) fiber -- the type found in legumes, oats, rye, barley and some fruits and vegetables -- can reduce LDL cholesterol (the bad kind, which correlates with heart attack risk). The NAS panel estimates that for every gram of soluble fiber you eat per day, you can reduce heart disease risk by 2.4 percent.

• High-fiber diets reduce triglycerides (fat in the blood), another risk factor for heart disease.

• New evidence has linked increased fiber intake to lower levels of C-reactive protein. The protein is an indicator of inflammation and an emerging risk factor for heart disease and other illnesses, according to Joanne L. Slavin, professor in the department of food science and nutrition at the University of Minnesota, St. Paul, and an expert on the NAS panel.

Reduced Risk of Colon Cancer In an ongoing study of 500,000 people in 10 European countries, the European Prospective Investigation into Cancer and Nutrition found that populations with low fiber consumption could reduce the risk of colorectal cancer by 40 percent simply by doubling their fiber intake.

There are several proposed theories of how fiber influences the risk of cancer. First, because fiber pulls water into the intestinal tract, it can dilute carcinogens and other tumor-promoting substances and cause them to exit the system in less time, resulting in less exposure to potentially damaging substances. A diet high in fiber also lowers the pH of the intestinal tract and reduces insulin levels, both of which are correlated with lower colon cancer risk. And the EPIC researchers stressed that foods supplying fiber also contribute many other nutrients and phytochemicals (beneficial plant chemicals) that have been linked to protection against cancer.

Although the majority of studies suggest that dietary fiber can be protective against colon cancer, a few recent studies found increased fiber intake did not result in a decrease in polyps, a precursor to cancer. Researchers have offered several theories as to why some studies fail to prove fiber's protective role against cancer. Benefits of dietary fiber may not occur until fiber intake is sufficiently high, and because Americans eat very low levels, measuring the effect is difficult. Also, the failed intervention studies used fiber supplements as opposed to fiber in foods.

Many researchers aren't convinced that the bulk of the health benefits comes from the fiber alone; some of the protection may instead come from the whole package of nutrients and phytochemicals found in high-fiber foods, which is why I recommend you get fiber from whole foods in your diet.

Katherine Tallmadge is a Washington nutritionist and the author of "Diet Simple" (Lifeline Press, 2004). Send e-mails to her at food@washpost.com.

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