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Pre-menopausal women who frequently consume red meat may be at higher risk of developing a certain type of breast cancer than pre-menopausal women who consume less red meat, according to the results of a new study. Most women who develop breast cancer have already reached menopause, but a small percentage develop the disease in earlier years. Past studies about the association between red meat and breast cancer risk have largely been inconclusive. Researchers of the current study do not know why pre-menopausal women who consume red meat several times a week may have a greater risk of breast cancer and say that further researcher is needed to explore this apparent connection. "This study suggests that dietary factors may be related to a woman's chance of developing this type of breast cancer, a disease that is on the rise in American women," said lead author, Eunyoung Cho, Sc.D, a researcher at Brigham and Women's Hospital in Boston, Massachusetts, in a news release. The study was published in the November 13, 2006 issue of the Archives of Internal Medicine. To conduct the study, researchers studied 90,659 pre-menopausal female nurses between the ages of 26 to 46 who are participating in the Nurses' Health Study II. The researchers followed the women from 1991 through 2003 and tracked their red meat consumption through a series of questionnaires. They also monitored whether the women developed breast cancer through the women's self-reports and hospital records. In total, 1,021 of the women developed breast cancer. Upon further analysis, the researchers found that how much red meat women consumed appeared to be linked to their breast cancer risk level. For example, women who consumed more than one and a half servings of red meat per day had nearly double the risk of a certain type of breast cancer compared with those with the lowest intake of red meat, which was less than three servings per week. It should be noted that red meat only appeared to increase the risk a certain type of breast cancer called hormone-receptor positive breast cancer. Many breast cancer cells contain estrogen or progesterone receptors; these cancers are called estrogen-receptor positive or progesterone-receptor positive (broadly, either are called hormone receptor positive breast cancer). Approximately 80% of breast cancers are estrogen receptor-positive; that is, they contain estrogen receptors. The remaining 20% are estrogen receptor-negative-they do not contain estrogen receptors. Out of the 1,021 women in the studied who developed breast cancer, 512 of them had hormone-receptor positive breast cancer. Previous studies on diet and breast cancer have largely yielded inconclusive results. In a 2002 British study of women who came to Britain from India, Pakistan, and Bangladesh, researchers found that those women who were lifelong vegetarians had a lower risk of developing breast cancer than those women who consumed meat. However, a 2000 study of nearly 400 women found no link between a high-fat diet and breast cancer. The researchers of the current study argue that many past studies focused on diet in women who had reached mid life or later, as opposed to younger women. "The reason why the amount of red meat consumed by a pre-menopausal women was related to her breast cancer risk is unknown, but this study shows that it has a strong association and that more research should be done to further explore this connection," said Cho. The link between diet and breast cancer will likely continue to be controversial. However, researchers have found that 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 Asia). 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). Risk factors for breast cancer include:
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