High-Fat Dairy Foods Linked to Worse Survival After Breast Cancer

Kroenke accounted for other factors that might play a role in cancer recurrence and death risk, such as stage of cancer at diagnosis, education level and other diet habits.

There were not enough women in the study to evaluate if the links between high-fat dairy and risk of death held for women with both ER-positive and ER-negative cancers, she said.

"I would expect to find a stronger link for ER-positive," she said.

Another expert commented on the new research.

"This is really one of the early studies of this topic," said Leslie Bernstein, director of the division of cancer etiology in the Beckman Research Institute at the City of Hope Comprehensive Cancer Center, in Duarte, Calif. She was not involved with the new study.

"It's an interesting finding,'' she said. But the researchers found an association, she said, not a cause-and-effect link. "The women were not [randomly assigned] to getting different diets."

Other factors could have played a part. For instance, eating patterns may be different right after diagnosis or treatment compared to earlier or later, she said.

The strongest result is for high-fat dairy and risk of death from other causes, she said.

High-fat diets can cause weight gain, a risk factor for heart disease. The women in the study who ate high-fat dairy may have died mostly from cardiovascular disease, Bernstein suggested, if they didn't die of breast cancer.

Both Kroenke and Berstein agreed more study is needed.

Meanwhile, it wouldn't hurt to eat low-fat dairy, Bernstein said.

"If women have breast cancer and are trying to reduce their estrogen exposure, shifting away from high-fat dairy to lower-fat dairy would make sense," Kroenke said.

SOURCES: Candyce Kroenke, Sc.D., M.P.H., staff scientist, Kaiser Permanente Division of Research, Oakland, Calif.; Leslie Bernstein, Ph.D., professor, and director, division of cancer etiology, Beckman Research Institute, City of Hope Comprehensive Cancer Center, Duarte, Calif.; March 14, 2013, Journal of the National Cancer Institute

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Published: March 2013