One thousand of the women in the study developed breast cancer. Half were diagnosed with a type of breast cancer that has been increasing in the United States, especially among middle-aged women. This type - characterized by hormones that promote tumor growth - is the one linked to red meat.
Lead author Eunyoung Cho of Harvard University says the more red meat consumed, the greater the risk of hormone receptor-positive breast cancer. "Pre-menopausal women who ate more than one and one half servings of red meat per day experienced almost double the risk of hormone-receptor positive breast cancer compared with those who ate less than three servings of red meat per week." The researcher suggests various components like carcinogens in uncooked meat or beef from cattle treated with growth hormone may be related to the elevated cancer risk.
While breast cancer is more common among older women, Cho says this study of younger women presents important health data for women as they age. "We thought that diet in early adult life may affect risk for breast cancer later in life."
Cho says more research must be done to evaluate the impact of a red meat diet over decades, but in the short term, reducing red meat consumption is better for overall health.
The study was published in the Archives of Internal Medicine, a publication of the American Medical Association.