Most of the livestock in the United States are treated with synthetic hormones, and some consumers worry that the hormones provide excess estrogen in the American diet. However, this is a controversial subject with limited valid research on either side of the debate. Estrogen and other hormones do naturally occur in animal proteins and certain other foods.
Estrogen is a naturally occurring sex hormone found in males and females. The role of estrogen in men is not understood; however, estrogen is important in the female reproductive system. Estrogen production in women is responsible for the development of female sexual organs. Estrogen hormones help to facilitate menstruation and control other metabolic processes, such as bone growth and cholesterol levels. Too much estrogen has been linked to different cancers, including breast cancer and endometrial cancer.
Synthetic Estrogen in Cattle
Growth-promoting hormones are implanted in most cattle in the United States. These hormones promote protein synthesis and result in cattle that are 10 to 30 percent larger than nontreated counterparts. Synthetic hormones in cattle mimic naturally occurring hormones in the animal. According to the University of Kentucky College of Agriculture, growth-promoting hormones used by the livestock industry have been extensively studied for safety and slight, if any, difference in hormones are noted in hormone-treated livestock.
Estrogen in Meat
Estrogen and other hormones occur naturally in livestock and can be found in small quantities in meat. The U.S. Department of Agriculture is unable to regulate the amount of growth hormones because it is impossible to differentiate the naturally occurring hormones from the synthetic type. However, the USDA does monitor meat from cattle for zeranol residues, a particular steroid hormone used to promote growth. Despite individual cases, it has not been scientifically proven that meat treated with hormones has any more estrogen than nontreated meat.
Red Meat and Breast Cancer Research
A major longitudinal study by Harvard Medical School and published in the “Archives of Internal Medicine” found that the consumption of red meat may be linked to breast cancer. Researchers followed 90,000 premenopausal women for 12 years. The participants who consumed the most red meat had nearly twice the risk of breast cancer as those who ate red meat infrequently. Although more research is needed, some researchers hypothesized that the growth hormones or naturally occurring hormones found in meat increased women’s estrogen production leading to breast cancer.
- University of Kentucky College of Agriculture; Growth-Promoting Implants for Beef Cattle; Jeff Lehmkuhler, et al.; March 2010
- Healthy Women; Estrogen; July 2011
- “Archives of Internal Medicine”; Red Meat Intake and Risk of Breast Cancer Among Premenopausal Women; Eunyoung Cho, et al.; November 2006
- Cornell University; Consumer Concerns About Hormones in Food; June 2000