High-fat Dairy Products Linked to Poorer Breast Cancer Survival
Patients who consume high-fat dairy products following breast cancer diagnosis increase their chances of dying from the disease years later, according to a study by Kaiser Permanente researchers.
The study, published in the Journal of the National Cancer Institute, is the first to examine the relationship between high-fat and low-fat dairy consumption following a diagnosis of breast cancer and long-term breast cancer survival. Previous studies have shown that higher lifetime exposure to estrogen is a causal pathway to breast cancer.
The researchers studied a cohort of women who were diagnosed with early-stage, invasive breast cancer between 1997 and 2000, primarily from Kaiser Permanente's Northern California region (83%) and the Utah Cancer Registry (12%).
Study Results
Those consuming larger amounts of high-fat dairy (one serving or more per day) had "higher breast cancer mortality as well as higher all-cause mortality and higher non-breast cancer mortality," wrote lead author Candyce H. Kroenke, ScD, MPH, staff scientist with the Kaiser Permanente Division of Research, and coauthors.
"Specifically, women consuming one or more servings per day of high-fat dairy had a 64% higher risk of dying from any cause and a 49% increased risk of dying from their breast cancer during the follow-up period," said Dr. Kroenke. The category of high-fat dairy products researchers tracked included cream, whole milk, condensed or evaporated milk, pudding, ice cream, custard, flan, and also cheeses and yogurts that were not low-fat or nonfat.
In general, the women studied reported that they consumed low-fat milk and butter most often, and they consumed relatively limited amounts of low-fat dairy desserts, low-fat cheese, and high-fat yogurt. Overall, low-fat dairy intake was greater (median 0.8 servings per day) than high-fat dairy (median 0.5 servings per day).
The study found an association between high-fat dairy and breast cancer mortality, but no association with low-fat dairy products and breast cancer outcomes.
"High-fat dairy is generally not recommended as part of a healthy diet," said senior author Bette J. Caan, DrPH, research scientist with the Kaiser Permanente Division of Research. "Switching to low-fat dairy is an easy thing to modify."
Design
Women entered into the cohort approximately 2 years after their breast cancer diagnosis. At the beginning of the study, 1,893 women completed a self-administered food-frequency questionnaire, and 1,513 of these women completed a follow-up questionnaire 6 years later. They were followed for 12 years on average following study entry.
The women were asked how often they consumed dairy foods during the previous year; what portion sizes they generally consumed; which products they ate, including milk, cheese, dairy desserts, yogurt, and beverages made with milk (such as hot chocolate or lattes); and whether the dairy products were full fat, low fat, or nonfat.
Of the total sample, 349 women had a recurrence of breast cancer and 372 died of any cause, 189 (50.8%) of them from breast cancer.
This research was part of the Life After Cancer Epidemiology (LACE) study, one of several efforts by investigators with the Kaiser Permanente Division of Research to consider the role of lifestyle factors such as nutrition, exercise and social support on long-term breast cancer survival and recurrence.
Authors of the study, in addition to Drs. Kroenke and Caan, were Marilyn L. Kwan, PhD, and Adrienne Castillo, MS, RD, of the Kaiser Permanente Division of Research; and Carol Sweeney, PhD, of the University of Utah Division of Epidemiology.
The National Cancer Institute of the National Institutes of Health funded this study (grant R01CA129059).
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
