Drinking dairy milk regularly is associated with a significantly greater risk of breast cancer in women, according to a recent study published in the International Journal of Epidemiology. “Consuming as little as one-quarter to one-third cup of dairy milk per day was associated with an increased risk of breast cancer of 30 percent,” lead researcher Gary E. Fraser, PhD, of Loma Linda University said. “By drinking up to one cup per day, the associated risk went up to 50 percent, and for those drinking two to three cups per day, the risk increased further to 70 to 80 percent.” For the study, the dietary intake of nearly 53,000 North American women, who were all initially cancer-free, was evaluated over the course of eight years. By the end of the study period, there were 1,057 new breast cancer cases among the women. While the study found no clear association between soy products and breast cancer, higher intakes of dairy calories and dairy milk were associated with a greater risk of breast cancer when compared to low or no dairy milk consumption, independent of soy intake. According to Fraser, the possible reasons for the increased risk may be the sex hormone content of dairy milk—since breast cancer in women is hormone-responsive cancer—and the intake of dairy and other animal products is also associated with higher blood levels of the insulin-like growth factor-1 hormone. “The data predicted a marked reduction in risk associated with substituting soy milk for dairy milk,” Fraser said. “This raises the possibility that dairy-alternative milks may be an optimal choice.” The study is part of the Adventist Health Study-2, a long-term health study exploring the links between lifestyle, diet, and disease within the Seventh Day Adventist community.
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