Breast cancer: low-fat finding.

Breast cancer: Low-fat-finding

The typical North American diet derives almost 40 percent of its calories from fat. Because many studies have linked such "high-fat" diets with increased breast-cancer risk, researchers from two Toronto hospitals decided to study whether year-long reductions in dietary fat would alter breast tissue in a potentially high-risk population. Their preliminary study, involving 180 women, found "hints" of a reduction in cancer risk. A report in the Oct. 5 JOURNAL OF THE NATIONAL CANCER INSTITUTE showed women who spent the year on a very low-fat diet developed fewer than half as many breast cancers as those on normal diets.

Participants were women whose routine mammograms exhibited "dysplasia" -- unusual shadows in the radiographic image -- affecting at least half a breast. Such changes are thought to signal increased breast-cancer risk. Half the women were encouraged to eat a typical diet -- containing about 37 percent of its calories from fat and 43 percent from carbohydrates. The rest ate a specially formulated diet deriving only about 15 to 20 percent of its energy from fat and 56 percent from carbohydrates. Periodic chemical measurements verified that all women stuck to their diets.

Mammograms one year later showed equal dysplasia in both groups but a difference in cancer incidence: Five women on the normal high-fat diet, but just two in the low-fat group, developed breast cancer. Although such a difference is consistent with animal diet research, the researchers were "very surprised" by it, says study coauthor Mary Cousins, at the Ontario Cancer Institute's Princess Margaret Hospital. "We didn't expect to see this in such a short period of time," she says.

With so few women involved, one should not make too much of the difference in cancer rates between the dietary groups--at least thus far, says Norman Boyd, the study's director. However, he notes, based on these early findings, a larger, follow-up study is in the works.