A new study has found that it is extremely important for women diagnosed with breast cancer to avoid high-fat dairy products because it increases their risk of dying from the disease. Researchers affiliated with Kaiser Permanente, Division of Research, published their findings on March 14 in the Journal of the National Cancer Institute.
The researchers note that dietary fat in dairy is a source of estrogenic hormones; thus, it may be related to worse breast cancer survival. Therefore, the investigators evaluated associations between high- and low-fat dairy intake, recurrence, and mortality after breast cancer diagnosis. The study group comprised 1,893 women from the Life After Cancer Epidemiology study diagnosed with early-stage invasive breast cancer from 1997 to 2000, who completed the Fred Hutchinson Cancer Research Center Food Frequency Questionnaire after diagnosis. During an average follow-up of 11.8 years, 349 women had a recurrence and 372 died; 189 deaths were due to breast cancer. The investigators used a method known as delayed entry Cox proportional hazards regression to evaluate associations between categories of the cumulative average of dairy fat at baseline and at follow-up five to six years later and subsequent outcomes.
The researchers found that overall dairy intake was unrelated to breast cancer–specific outcomes; however, it was positively related to overall mortality. Low-fat dairy intake was unrelated to recurrence or survival. However, high-fat dairy intake was positively associated with outcomes. Compared with the reference (0 to less than 0.5 servings/day), women who consumed larger amounts of high-fat dairy had higher breast cancer mortality (0.5 to less than 1.0 servings/day; 1.20-fold increased risk); women who consumed more than 1.0 servings/day had a 1.49-fold increased risk as well as an increased all-cause mortality, and higher non–breast cancer mortality. The researchers noted that the relationship with breast cancer recurrence was positive but not statistically significant. The higher risk appeared consistent across different types of high-fat dairy products.
The researchers concluded that intake of high-fat dairy, but not low-fat dairy, was related to a higher risk of mortality after breast cancer diagnosis.