Eating more red meat may be associated with a higher risk for hormone receptor–positive breast cancers in premenopausal women, according to the new report.

“Breast tumors are often characterized by hormone (estrogen and progesterone) receptor status,” the authors write as background information in the article, meaning that the cancer is classified by whether these hormones can bind to proteins on the surface of the tumor.

“Although the incidence rates of hormone receptor–negative tumors have remained relatively constant, the incidence of hormone receptor–positive tumors has been increasing in the United States, especially among middle-aged women.”

The diets of American women may be linked to this increase, since some foods — including certain components of red meat — can contain hormones or hormone-like compounds that influence tumors through their hormone receptors.

Eunyoung Cho, Sc.D., Brigham and Women’s Hospital and Harvard Medical School, Boston, and colleagues studied 1,021 women that had developed breast cancer, including 512 cases that were estrogen and progesterone receptor positive.

The highest intake of red meat was not significantly associated with the risk for breast cancer overall or for hormone receptor–negative cancers, but was associated with an increased risk for hormone receptor–positive cancer.

Women who ate more than one and one-half servings of red meat per day - steaks, burgers, roast beef and likes - had almost double the risk of hormone receptor–positive breast cancer compared with those who ate three or fewer servings per week.

The associations remained similar when the researchers calculated red meat intake in grams instead of servings, and also when they split the women into five groups based on how much red meat they ate.

“Several biological mechanisms may explain the positive association between red meat intake and hormone receptor–positive breast cancer risk,” the authors write.

Known cancer-causing compounds in cooked or processed red meat increase mammary tumors in animals and have been suspected of causing breast cancer in humans.

In addition, cattle in the United States are treated with hormones to promote growth, which could also influence breast cancer risk. The type of iron available in red meat also may enhance tumor formation. 

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