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High-Fat Dairy Products Reduce Breast Cancer Survival
Women who consume high-fat dairy products after a diagnosis of breast cancer increase their chances of dying from the disease years later, according to a recent study published in the Journal of the National Cancer Institute.
Previous studies have shown that higher lifetime exposure to estrogen is a causal pathway to breast cancer. Estrogen levels are believed to be elevated in dairy products consumed in the Western world because most of its milk comes from pregnant cows. Estrogenic hormones reside primarily in fat, so levels are higher in high-fat dairy products than in low-fat ones.
Researchers at Kaiser Permanente 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%).
The researchers found that women 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.
“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 lead author Candyce H. Kroenke, ScD, MPH.
The category of high-fat dairy products that researchers tracked included cream, whole milk, condensed or evaporated milk, pudding, ice cream, custard, and flan, as well as cheeses and yogurts that were not low-fat or non-fat.
In general, the women reported that they consumed low-fat milk and butter most often, and that 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 intake (median 0.5 servings per day).
The study found an association between high-fat dairy products and breast cancer mortality, but no association between low-fat dairy products and breast cancer outcomes.
Women entered the study 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. The women were followed for an average period of 12 years.
Source: Kaiser Permanente; March 14, 2013.