There’s no evidence that a high fat diet predisposes older women to breast cancer, researchers from Harvard Medical School report.
It has long been thought that dietary fat can increase production of sex hormones, including estrogen, which could put women at risk for breast cancer, especially older women. But this study of 381 postmenopausal women – the largest and most detailed of its kind – found just the opposite.
The researchers found that women in the study who ate less fat than typical 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. It’s one less thing they need to worry about if they are concerned about breast cancer,” said the study’s lead author, Michelle Holmes, MD, DrPH. “We found no evidence that higher fat intake is associated with higher levels of any reproductive hormones in this group of postmenopausal women.”
Dr. Holmes added that lowering fat intake to reduce hormone levels, and thus risk of breast cancer, probably isn’t a useful strategy. “It does not seem likely that eating a low-fat diet in mid-life can lower hormone production,” Holmes said.
The research team took blood samples from the study participants to measure the amount of hormones present in their blood. Those hormones included estradiol, which produces estrogen – the female hormone most associated with breast cancer risk – as well as “male” hormones such as testosterone. Researchers also estimated the different kinds of fat the women ate, based on a food survey participants answered twice during the four-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 – including estradiol and testosterone – went down.
“Dietary Fat Intake and Endogenous Sex Steroid Hormone Levels in Postmenopausal Women;” Michelle D. Holmes, MD, DrPH, et al.; Harvard Medical School and Brigham and Women’s Hospital, Boston, MA. Vol. 18, No. 21 (November 1), 2000: pp 3668-3676.
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