Patients with breast cancer who consume high-fat dairy products have poorer survival rates years later, according to a Kaiser Permanente study published in the Journal of the National Cancer Institute.
The study, led by Candyce Kroenke, ScD, MPH, staff scientist with the Kaiser Permanente Division of Research in Oakland, California, is to the authors' knowledge the first to analyze the connection between high-fat and low-fat dairy consumption and long-term breast cancer survival. Other studies have shown a link between lifetime estrogen exposure and breast cancer, and estrogen is believed to be increased in dairy products in the Western world because most milk is produced by pregnant cows. Furthermore, estrogen levels are higher in high-fat dairy products than in low-fat products.
Dr. Kroenke and her colleagues examined a group of women primarily from Kaiser's Northern California region and the Utah Cancer Registry who were diagnosed with early-stage, invasive breast cancer between 1997 and 2000. The women entered the study approximately 2 years after being diagnosed, and they completed a self-administered food frequency questionnaire. After 6 years, the participants completed a follow-up questionnaire and were followed for 12 years on average.
The study's findings indicated that women who consumed 1 or more servings per day of high-fat dairy had a 64% higher risk of dying of any cause and a 49% higher risk of dying of breast cancer. Among the highfat dairy products followed were cream, whole milk, condensed or evaporated milk, pudding, ice cream, custard, flan, and cheese or yogurts that were not low fat or nonfat. While the study demonstrated a link between high-fat dairy consumption and breast cancer mortality, it did not find an association between low-fat dairy intake and deaths from the disease.
The study was part of the Life After Cancer Epidemiology (LACE) study, which is research performed by Kaiser Permanente Division of Research scientists to evaluate the impact of nutrition, exercise, and social support on long-term breast cancer survival and recurrence. Many studies focus on lifestyle factors and cancer prevention, but this study is part of a small but growing number to examine the role these factors play after a breast cancer diagnosis. The researchers are hoping to generate results that will help guide women as they make decisions after a breast cancer diagnosis.