Diet Can Lessen Cancer Risk, Study Says : Health: Men who eat low-fat, high-fiber foods sharply reduce their chance of developing polyps that lead to the disease, researchers report.
Men who eat a low-fat, high-fiber diet can dramatically reduce their chance of developing certain benign tumors that lead to intestinal cancer, according to a new study that adds data to the growing debate over the role of diet in cancer.
The researchers, at Harvard University, found that men with high-fiber diets had one-third the rate of colon polyps of men with low-fiber diets. Similarly, men with low-fat diets had half the rate of polyps found in men with the highest fat intake.
“It’s pretty well established that most (colon) cancers arise from polyps,” said Dr. Edward Giovannucci, an author of the study, which was reported on Monday in Atlanta at the annual meeting of the Foundation of American Societies for Experimental Biology. “. . . If diet is important in the early stages of carcinogenesis, it may be important to study polyps.”
An estimated one-third of all cancer deaths may be related to diet. That’s at least as many as can be traced to tobacco. Yet what it is that promotes cancer--or protects against it--remains unclear. Dietary fats and fiber have attracted the greatest interest.
Giovannucci’s study is the first so-called prospective study to find a clear link between fat, fiber and colon polyps, he said. A prospective study is one in which researchers follow participants over time, rather than studying them retrospectively.
In the study, the high-fiber group ate more than 28 grams of fiber a day--perhaps twice the level in the average American’s diet. The men in the low-fat group took in an average of 24% of their calories as fat, a level much lower than that of the average American.
Giovannucci said men could probably reduce their risk of polyps by eating two servings a day each of fruits, vegetables and unrefined cereal products. He said fiber may help prevent the earliest stages of cancer, while fat may precipitate its development later on.
In a related study, also presented at the Atlanta meeting, federal researchers concluded that merely modest reductions in fat intake cannot significantly reduce cancer risk.
Dr. Tim Byers of the U.S. Centers for Disease Control found no significant difference in the rates of breast, prostate and colon cancer among men and women on relatively high- and low-fat diets in a group of more than 13,000 Americans followed over 20 years.
But the differences in fat intake between the two groups were slim; both groups took in more than 30% of their calories in the form of fat. So the study was unable to explore the effects of a genuinely low-fat diet on, for example, breast cancer risk.
“The conclusion must be that if lowering fat intake is going to reduce breast cancer, it will do so very minutely,” said Byers, chief of epidemiology in the division of nutrition. “Or, we have to reduce fat intake more substantially than we do.”
Byers emphasized that there are compelling reasons, such as reducing heart disease and obesity, for cutting down on fat in the American diet even though studies have produced seemingly contradictory results on the role of fat in cancer.
