High-Fat Diet Not Associated With Increased Estrogen in Postmenopausal Women

There is no evidence that a high-fat diet predisposes older women to breast cancer, report researchers from Harvard Medical School. It has long been thought that dietary fat can increase production of sex hormones, including estrogen, and thus put women (especially older women) at risk for breast cancer. This study in 381 postmenopausal women, however, revealed just the opposite. The researchers found that women in the study who ate less fat than is typical among US women actually had higher levels of estrogen in their blood, making it unlikely that eating a low-fat diet will lead to lower levels of estrogen.

"This is good news for women," said the study’s lead author, Michelle Holmes, MD, DrPH, assistant professor of medicine at Harvard Medical School. "It’s one less thing they need to worry about if they are concerned about breast cancer. We found no evidence that higher fat intake is associated with higher levels of any reproductive hormones in this group of postmenopausal women."

Lower Fat Intake Leads to Higher Hormone Levels

Dr. Holmes added that lowering fat intake to reduce hormone levels, and thus the risk of breast cancer, probably is not a useful strategy. "It does not seem likely that eating a low-fat diet in midlife can lower hormone production," said Dr. Holmes.

The research team took blood samples from study participants to measure the amount of hormones present in their blood. Those hormones included estradiol(Drug information on estradiol) as well as "male" hormones such as testosterone. Researchers also estimated the different kinds of fat the women ate, based on a food survey conducted twice during the 4-year study. None of the women were using hormone replacement therapy.

The researchers found that as women increased the amount of fat in their diets, the levels of six hormones declined. The study results were published in a recent issue of the Journal of Clinical Oncology (18:3668-3676, 2000).