A new study has failed to find a clear-cut connection betwee dietary fat and breast cancer. But researchers and commentators cautioned that it was too early to rule out a link.
In the study, being published today in the Journal of the National Cancer Institute, researchers analyzed the body fat of 380 women newly diagnosed with breast cancer, and compared the findings with a similar fat analysis of 176 women with benign breast disease and 397 women without any breast disease.
Since the constituents of body fat represent dietary habits going back at least two years, the analysis is believed to reflect people's dietary habits more accurately than just asking them what they eat.
The researchers, from Los Angeles and Boston, checked the body fat samples for levels of saturated, monounsaturated, polyunsaturated, trans and omega-3 fatty acids. Laboratory studies have suggested that intakes of saturated, polyunsaturated and trans fatty acids, formed during the processing of polyunsaturated fatty acids, may promote cancer, while omega-3 fatty acids, found primarily in fish, may be protective.
The researchers also examined the women's blood and diet for levels of antioxidant nutrients, including vitamin E and beta-carotene, which are thought to protect against cancer.
The team, headed by Dr. Stephanie J. London, now at the University of California at Los Angeles, found no statistically significant relationship between any of the fat constituents or levels of antioxidants and the women's chances of having breast cancer or benign breast disease.
Dr. London and her collaborators, from Harvard's Medical School and School of Public Health and Massachusetts General Hospital, concluded that intake of the various fatty acids "at least in the range experienced in the American diet" did not seem to influence the risk of breast cancer risk.
But the findings do not prove that no relationship exists. As stated in an accompanying editorial by Dr. Alice S. Whittemore of the Stanford University School of Medicine and Dr. Brian E. Henderson of the Salk Institute for Biological Sciences in La Jolla, Calif., a person's body fat composition reflects only the type, not the amount, of fat habitually eaten.
Studies of breast cancer rates in different countries and animal experiments suggest that the more fat habitually in the diet, the higher the likelihood of developing breast cancer.
But looking only at American women, a link between fat intake and the risk of breast cancer has been hard to establish.
One reason may be that fat intake early in life, not necessarily around the time breast cancer develops, may be the strongest influence on future risk, and no studies to date have measured this.
Another possibility is that the levels of fat in the diets of American women are not different enough to discern a difference in cancer risk related to eating habits.