Postmenopausal women diagnosed with breast cancer had a reduced risk of death if they ate a low-fat diet, a new study finds. But the effect was small and other studies disagree.

Why it matters:

Studies on how people’s diets affects their risk of breast cancer have had mixed findings. Some observational studies have found that higher fat intake correlates with higher breast cancer incidence, but two randomized clinical trials failed to show the same effect.

The nitty gritty:

This randomized trial included nearly 50,000 women, ages 50 to 79, with no prior breast cancer. Researchers split them roughly in half: 20,000 people were assigned to eat a low-fat diet under the supervision of a nutritionist, while the control group followed their usual dietary patterns.

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The goal of the low-fat diet was to reduce fat intake to 20 percent of calories consumed and to increase the consumption of fruits, vegetables, and grains.

After approximately eight years of the study, 1,767 of the overall group had been diagnosed with breast cancer. The rate of survival was 82 percent for those in the dietary group, versus 78 percent for the control group. The study was presented at the American Association for Cancer Research (AACR) annual meeting.

But keep in mind:  

The study hasn’t been peer-reviewed. “I am very skeptical,” said John Pierce, a professor and cancer researcher at University of California, San Diego. In his team’s previous study of breast cancer survivors, he said, “we were unable to find any effect from a major change in vegetables, fruit, fiber, and fat.” He added that the earlier study included a smaller amount of dietary fat than the recent study.

Lead author Dr. Rowan Chlebowski, professor of medicine at the University of California, Los Angeles, admitted that his findings are “a hypothesis from secondary analysis in a randomized trial.” That trial, designed to assess whether a low-fat diet decreased a woman’s risk of getting breast cancer in the first place, found that it didn’t. “But it’s intriguing,” he added.

Bottom line:

There are plenty of reasons to reduce fat intake, but it’s unclear whether better breast cancer survival is one of them.

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