The fat in dairy is a source of estrogenic hormones. Some scientists suspect that these dietary hormones may increase the likelihood of breast cancer.

A new study evaluated whether high- and low- fat dairy was related to worsened breast cancer survival.

The study included 1,893 women who had been diagnosed with early-stage invasive breast cancer between 1997 and 2000. Participants completed the Fred Hutchinson Cancer Research Center Food Frequency Questionnaire after diagnosis.

The consumption of high-fat dairy was shown to put patients at a greater risk of mortality from breast cancer. The study showed that eating at least half a serving of high-fat dairy per day increased the risk of dying from the disease.

The authors of the study note that women diagnosed with breast cancer have dietary alternatives to high-fat dairy. The study found no correlation between low-fat dairy consumption and risk of recurrence or death. "Consuming plant-based milks or nonfat dairy products may be a reasonable approach for limiting risk of adverse outcomes," they wrote.

Dairy consumption has previously been linked to other hormonal cancers, such as prostate, endometrial, and ovarian cancers.

Reference

Kroenke C, Kwan M, Sweeney C, Castillo A, Caan B. High- and Low-Fat Dairy Intake, Recurrence, and Mortality After Breast Cancer Diagnosis. Journal of the National Cancer Institute 2013; doi: 10.1093/jnci/djt027.