Fat Acquitted as a Risk Factor in Breast Cancer

By William J. Cromie

Gazette Staff

Whatever else it may do, eating fatty food won't increase your risk of getting breast cancer.

That's the conclusion of researchers at the School of Public Health (SPH) and the Medical School who participated in the largest study to date on the association between fat in the diet and a cancer that kills more than 46,000 women and men each year.

"We looked at the results of seven studies, which included more than 335,000 women in four countries," said David Hunter, associate professor of epidemiology at SPH. "No reduction in risk was found at levels of fat intake far below the average in the United States, or for saturated versus unsaturated fat. Therefore, it appears unlikely that a reduction in total fat consumption by middle-aged and older women will substantially reduce their chances of getting breast cancer."

According to the American Cancer Society, about 186,000 women and 1,000 men will be diagnosed with breast cancer this year.

Fat Controversy

This research goes a long way toward settling a controversy that has gone on for more than 50 years. Several previous studies found a positive link between fat intake and increased risk of breast cancer. These investigations, however, involved asking women about their diet after they developed the disease.

Such results can be biased by inaccurate recall of what was eaten. "The experience of being diagnosed with, and treated for, breast cancer may well alter a women's recall of her past diet," Hunter notes.

He and his colleagues looked only at studies in which large samples of healthy women were followed for as long as seven years to determine who got the cancer. The investigation covered females from the United States, Canada, the Netherlands, and Sweden whose fat intake ranged from less than 20 to more than 30 percent of calories eaten. (The average in this country is 33 percent.) The women, who ranged in age from 28 to 90 years, included Adventists in California and more than 89,000 participants in Harvard's long-running Nurses' Health Study.

Almost 5,000 of the women got breast cancer. However, their disease was not linked to total, saturated, monosaturated, polyunsaturated, animal, or vegetable fat, or cholesterol levels.

"The study comes as close as one can get to showing that fat intake is not related to the incidence of breast cancer," Hunter maintains.

It is possible to do a more accurate test by following two groups of women, one that limits fat intake to 20 percent or less of calories and one that does not. Such a study, the Women's Health Initiative, is now under way, but findings are not expected until the end of the century.

The present study showed no reduction in breast cancer at the 20 percent level, and other studies in China found no significant relationship even at levels as low as 15 percent.

Although women can feel less guilty about enjoying an occasional cheeseburger and fries, no physician would advise wild abandon at the dinner table. Fat is still a major factor in other malignancies such as colon cancer, and a suspect in heart disease and diabetes.

"There is good evidence that reducing red meat, dairy products, and other sources of fat protects men and women against colon cancer," Hunter says.

Details of the research were reported in today's edition of The New England Journal of Medicine by Hunter and 17 co-authors from Harvard-affiliated and other institutions in four states and four countries.