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Though some studies and anecdotal evidence has suggested a link between diet and breast cancer, a large study of nurses finds that the consumption of any kind of meat or eggs does not increase the risk of developing breast cancer. Unlike other studies that rely on women recalling what they have eaten in the past, this study followed women for 18 years to study the association between diet and breast cancer. However, the researchers do note that red meat is linked to a higher risk of other diseases, such as heart disease. To study the correlation between diet and breast cancer risk, Dr. Michelle D. Holmes of Harvard Medical School and Brigham and Women's Hospital and colleagues followed 88,647 women for 18 years and assessed their diet at five different intervals. Questionnaires inquired about specific dietary habits. At the end of the study, the researchers found no evidence that consuming any kind of meat, including fish, or eggs increased the risk of developing breast cancer. Past studies on diet and breast cancer have yielded mixed results. The general consensus has been that monounsaturated fats, such as canola oil or olive oil, may lower breast cancer risk while diets high in polyunsaturated fats, such as corn oils, tub margarine, and saturated fats in meats, have been associated with a higher risk of breast cancer. However, this latest study seems to contradict the link between meat and breast cancer risk. Another food, soy, has also been linked to breast cancer, in a positive way. Small studies have suggested that a diet rich in soy may reduce the risk of developing breast cancer (though further research is needed). Researchers are also unsure howsoy may work to protect against breast cancer risk. In a study published in the July 2002 issue of Cancer Epidemiology Biomarkers & Prevention, Rupert W. Jake of Yu National Medical Research Council Clinical Trials and Epidemiology Research Unit in Singapore and colleagues suggested that soy may extend women’s menstrual cycles. Fewer menstrual cycles over a lifetime have been associated with a reduced risk of breast cancer. Other research focuses more on the contents of soy. For instance, soy contains natural chemicals called phytoestrogens, which may work as anti-estrogens against breast cancer development, similar to the breast cancer prevention drug tamoxifen. The theory is that soy, like the drug tamoxifen, blocks the hormone estrogen from binding to estrogen receptors in breast cancer cells. Since some breast cancer cells depend on estrogen for survival, a lack of estrogen starves these cells, causing them to die. The link between diet and breast cancer is likely to remain controversial. There is a much higher incidence of breast cancer in areas with high fat diets (such as the United States) than areas with low-fat diets (such as Japan). However, researchers have identified other factors that seem to play a larger role in determining breast cancer risk (although 80% of women diagnosed with breast cancer have no known risk factors). These factors include:
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