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Breast Cancer Health Center

High-Fat Diet Linked to Breast Cancer

Study Shows Modest Increase in Breast Cancer Risk for Postmenopausal Women
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WebMD Health News
Reviewed by Louise Chang, MD

March 20, 2007 -- There is more evidence linking high-fat diets to a modest increase in breast cancer risk among older women. But all agree that more study is needed to prove an association once and for all.

In the largest study ever to address the issue, researchers from the National Cancer Institute (NCI) asked 188,736 postmenopausal women about the foods they ate and then followed the women for an average of 4.4 years.

They found that women whose diets included the most fat were 15% more likely to develop breast cancer than women who ate the least fat. The association was seen both in women who were overweight and those of normal weight.

"Fifteen percent is modest, but it could have a huge impact because breast cancer is so common," researcher Anne C. M. Thiebaut, PhD, tells WebMD. "This is certainly an issue that deserves further investigation."

Many Studies, Little Consensus

Researchers have been studying the question for decades, but there is still little consensus on whether fat intake influences breast cancer risk. In a recent analysis of 14 studies, women who ate the most fat had a 13% higher risk of breast cancer compared with women who ate the least.

Eating a low-fat diet was found to reduce breast cancer risk by 9% in a recently reported Women's Health Initiative intervention trial. This association was considered marginally statistically significant, meaning it was not likely due to chance.

In the newly published study, Thiebaut and NCI colleagues followed women between the ages of 50 and 71 participating in the larger National Institutes of Health-AARP Diet and Health Study.

The participants completed a detailed survey to determine their dietary habits at study entry. During the 4.4-year average follow-up, 3,501 of the women developed breast cancer.

Compared with women whose diets averaged 20% of calories from fat, women who derived roughly 40% of their calories from fat sources had a 15% increased risk for developing breast cancer.

The types of fats the women ate appeared to have little bearing on risk. No additional increase in risk was seen among women who ate large amounts of saturated fats, as has been suggested in several other studies.

Thiebaut and colleagues conclude that their findings "should contribute to the ongoing debate about the association between dietary fat and the risk of breast cancer."

The study appears in the March 21 issue of the Journal of the National Cancer Institute.

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