HARVARD GAZETTE ARCHIVES

Researchers at Brigham and Women's Hospital (BWH) have found that eating more red meat may be associated with a higher risk for hormone receptor–positive breast cancers in premenopausal women. This research is published in the Nov. 13 issue of the Archives of Internal Medicine.

"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, a researcher at BWH.

Hormone receptor-positive breast cancers are characterized by tumors in which growth is stimulated by the levels of estrogen (ER+) or progesterone (PR+) circulating in the body. Previous studies that have examined the association between breast cancer and red meat assessed diet in midlife or later, did not distinguish by hormone receptor status, and are largely inconclusive. 

In this study, researchers evaluated the association between breast cancer and red meat consumption in 90,659 female nurses aged 26 to 46 who are part of the Nurses' Health Study II. The researchers followed the participants from 1991 through 2003, and gathered data on red meat consumption and breast cancer development.

Out of this group, which excluded postmenopausal women and those who had previously had cancer, researchers identified 1,021 women who had developed breast cancer. Among those with information on hormone-receptor status, 512 cases were ER+/PR+.

The researchers split the women into five groups based on how much red meat they ate and found that the highest intake of red meat, more than one-and-a-half servings per day, had nearly double the risk for hormone receptor–positive cancer compared with those with the lowest intake of red meat, which was less than three servings per week. 

Researchers suggest several biological factors that may be related to the association between red meat and ER+/PR+ breast cancer including carcinogens found in cooked or processed red meat, hormone treatments of cattle for growth purposes, and the type of iron found in red meat.

"The reason why the amount of red meat consumed by a premenopausal woman 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, who is also an assistant professor of medicine at Harvard Medical School.

This research was supported by the National Institutes of Health.