Eating Healthy Lowers Cancer Risk

Sept. 20, 2002 -- Eating right, exercising regularly, keeping your weight down -- we've heard before that "being good" keeps disease at bay. Now a new study points to diet as an important factor in preventing cancer for women past menopause.

But critics argue that for postmenopausal women, lifestyle habits such as exercise, weight control, and quitting smoking are even more important than angelic eating habits, says Marji McCullough, ScD, RD, a senior researcher with the American Cancer Society.

"Diet may play a stronger role for protecting against cancer earlier in life," McCullough tells WebMD.

The study and McCullough's editorial appear in the October issue of the American Journal of Clinical Nutrition.

In the study, researchers randomly selected 34,708 women from rural Iowa, all postmenopausal. In 1985, the women completed a comprehensive questionnaire, giving great detail about foods they ate, activity level, alcohol intake, and habits such as smoking.

The study specifically focused on women's adherence to the USDA's "Dietary Guidelines for Americans," which advocate:

• Eating a variety of foods
• Choosing a diet with plenty of grain products, vegetables, and fruits
• Choosing a diet low in fat, saturated fat, and cholesterol
• Choosing a diet moderate in sugars, salt, and sodium
• Drinking moderately, if you drink at all.
• Balancing the foods you eat with physical activity, to maintain or improve weight.

For 13 years, researchers kept track of the women's health status, says lead author Lisa Harnack, an epidemiologist with the School of Public Health at the University of Minnesota in Minneapolis.

Harnack and colleagues found that women who were more active, ate more grain and less fat in their diet, and did not smoke had 15% fewer cancers. These women were also more likely to take hormone replacement therapy. Exercise and weight also seemed to make a difference, she says.

The significant reductions were in uterine, breast, lung, and colon cancer among those who followed dietary guidelines, says Harnack.

"We applaud such evaluations of diet guidelines," writes McCullough in her editorial. "Few studies have evaluated whether people who follow the dietary guidelines actually remain healthier."

However, McCullough's analysis of Harnack's data shows a different story -- that weight and physical activity had the strongest influence on the results, she tells WebMD. In other words, if regular exercise and maintaining a healthy weight were taken out of the formula, the effect of diet on cancer would be modest.

"Together with the lower risk of cancer if you don't smoke, these results underscore that postmenopausal women can make lifestyle changes to reduce their risk of getting cancer," McCullough says.

Diet may play a greater protective role earlier in a woman's life. Also, "the role of diet in cancer is likely to vary by cancer type, stage of cancer development, and genetics," she says. "We still have a lot to learn about diet and cancer, but we are moving forward."