Q.I always thought cutting back on fat would help reduce my risk of breast cancer. Now I hear a new study says it won’t. Should I worry less now about my fat intake?A. Not really. First of all, the results of any one study shouldn’t dictate major alterations in diet. Second, there are other reasons to watch your fat intake.
The research you mention appeared in the March 10th Journal of the American Medical Association, based on a Harvard study of nearly 89,000 women followed for 14 years. Researchers analyzed the women’s diet records and breast cancer occurrence. They found no evidence that a lower intake of fat-as low as 20% of calories-or even intakes of specific types of fat (animal, vegetable, polyunsaturated, saturated, monounsaturated, trans, cholesterol or omega-3 fatty acids) affected the risk of breast cancer.
But while the Harvard researchers are convinced there’s no connection between fat intake and breast cancer, many experts in the field believe the controversy is far from settled. “There are many mechanisms at play that we don’t yet fully understand,” says Rachel Ballard-Barbash, M.D., M.P.H., of the National Cancer Institute.
Just one week after the Harvard study appeared, a research team at the University of Southern California Medical School in Los Angeles directly contradicted the Harvard study while reporting on one of those little-understood mechanisms. The researchers announced that reducing fat below 20% of calories is associated with a reduction in blood estrogen levels, which they suggest may reduce the risk of breast cancer.
The USC researchers pooled the findings of 13 studies conducted over the past 30 years, publishing their analysis in the March 17th Journal of the National Cancer Institute. Unfortunately, the results of more than a third of the studies included in the analysis have been questioned because other factors-such as a higher fiber intake-might have contributed to the lower estrogen levels. Also, in some of the studies, many of the women lost weight, which by itself has been shown to lower estrogen levels.
The upshot? We probably haven’t heard the final word on dietary fat’s effect on breast cancer risk. But there are still plenty of good reasons to cut back on fat, the biggest being protection against heart disease, the number one killer of women, as well as against other cancers and obesity. Perhaps more important, evidence is accumulating that improving the mix of fats in the diet-more monounsaturated fat, less polyunsaturated, saturated and trans fats-can improve the odds against disease.
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