Consumption of high-fat dairy products following a breast cancer diagnosis increases mortality, according to a recent study.

Dietary fat in dairy is a source of estrogenic hormones and may be related to poorer breast cancer survival, explained Candyce H. Kroenke, ScD, MPH, and colleagues in Journal of the National Cancer Institute. Kroenke, a staff scientist with the Kaiser Permanente Division of Research in Oakland, California, and her team sought to evaluate associations between high-fat and low-fat dairy intake and recurrence and mortality after breast cancer diagnosis.

The researchers analyzed data from 1,893 women participating in the Life After Cancer Epidemiology (LACE) study. All had received a diagnosis of early-stage invasive breast cancer between 1997 and 2000, and all had completed the Fred Hutchinson Cancer Research Center (Seattle, Washington) Food Frequency Questionnaire postdiagnosis. As noted in an accompanying statement from Kaiser Permanente, the category of high-fat dairy products tracked by Kroenke and co-investigators included cream, whole milk, condensed or evaporated milk, pudding, ice cream, custard, flan, and cheeses and yogurts that were not low-fat or nonfat.

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During a median follow-up of 11.8 years, 349 women had a recurrence and 372 women died. Half the deaths (189, or 50.8%) were due to breast cancer.

Kroenke’s team found that overall, low-fat dairy intake was greater (median 0.8 servings per day) than high-fat dairy intake (median 0.5 servings per day) among the women studied. Multivariable–adjusted analyses indicated that overall dairy intake was not related to breast cancer–specific outcomes, but was positively related to overall mortality. Low-fat dairy intake was unrelated to recurrence or survival.

High-fat dairy intake, however, was positively associated with outcomes: Compared with the reference of 0 to less than 0.5 servings per day, women consuming one or more daily servings of high-fat dairy products had a 49% greater risk of breast cancer mortality and a 64% greater risk of all-cause mortality. The heightened risk appeared consistent across different types of high-fat dairy products.

A positive relationship was also seen in terms of breast cancer recurrence, but the association was not statistically significant.