In all, 349 women had a cancer recurrence over the follow-up period. Of the 372 women who died during that time, 189 deaths (about half) were due to breast cancer.
The researchers divided the women into three groups, from low to high intake of high-fat dairy foods.
The lowest group ate less than a daily half-serving (or none) of high-fat dairy. The highest group had a serving a day or more.
One limitation, Kroenke said, is the reliance on self-reported food records, subject to mistakes as no one remembers perfectly. So the link between high-fat dairy and death risk may be underestimated, she said.
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
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