rBGH & Breast Cancer

The Connection Between rBGH and Breast Cancer

Recombinant Bovine Growth Hormone (rBGH), also known as Recombinant Bovine Somatotropin (rBST), is injected into cows so they will produce more milk. Research suggests that a number of health concerns, including breast cancer, are associated with the consumption of dairy products from cows treated with rBGH.

The use of rBGH stimulates the production of another hormone called insulin-like growth factor 1 (IGF-1), a naturally occurring hormone in both cows and humans that regulates cell growth, division, and differentiation. 1  2

Cow’s milk that is treated with rBGH has higher levels of IGF-1. Studies in humans, animals, and cell cultures have indicated that elevated levels of IGF-1 in humans may increase the risk of breast cancer. 3 4 5

In addition to breast cancer, increased IGF-1 levels have been associated with prostate, colon, and other cancers.6 The use of rBGH also increases the need for antibiotics in cows, which can lead to increased antibiotic resistance in humans.7

There is controversy about whether or not the IGF-1 in milk makes its way into the human bloodstream. Some studies have indicated that IGF-1 does survive digestion while others have not. 8 What is clear is that there is sufficient evidence for concern about the human health impacts of using rBGH.

rBGH has been used, without labeling, in the United States since its approval in 1993, making it difficult for consumers to make informed purchases. Dairy companies in the U.S. that use milk from untreated cows may voluntarily label their products rBGH-free, but this right has recently come under attack.

The good news is that consumers are demanding rBGH-free dairy products, and corporations are taking note. In addition to the many dairy companies that offer rBGH-free products, huge retailers and food and beverage chains like Walmart, Publix, Kroger, Starbucks, and Chipotle have committed to reducing or completely eliminating dairy products made with rBGH from their stores. In response to BCA’s “Yoplait: Put a Lid On It” campaign, General Mills committed to using only rBGH-free dairy. Soon after, Dannon followed suit.

The use of rBGH has been banned entirely in Australia, Canada, Japan, and all 27 countries in the European Union. Although there is not definitive proof that the use of rBGH leads to breast and other cancers, there is enough evidence now to take precautionary steps and to eliminate its use.



  1. European Commission. Report on Public Health Aspects of the Use of Bovine Somatotrophin. Food Safety—From the Farm to the Fork. March 15-16, 1999.
  2. Prosser C.G., et al. Increased secretion of insulin-like growth factor 1 into milk of cows treated with recombinantly derived bovine growth hormone. Journal of Dairy Research 56 (1) 17-26, 1989.
  3. Hankinson S, et al. Circulating concentrations of insulin-like growth factor 1 and risk of breast cancer. Lancet 351:1393-1396, 1998.
  4. Macaulay VM. Insulin-like growth factors and cancer. British Journal of Cancer 65:311-320, 1998.
  5. Resnicoff M, Baserga R. The insulin-like growth factor 1 receptor protects tumor cells from apoptosis in vivo. Cancer Research 55:2463-69, 1998.
  6. Yu, Herbert and Thomas Rohan. Role of the Insulin-Like Growth Factor Family in Cancer Development and Progression. Journal of the National Cancer Institute 92:1472-89, 2000.
  7. Kronfield D. Recombinant bovine somatotropin and animal welfare. Journal of the American Veterinary Medical Association 216(11):1719-1720, 2000.
  8. Xian C. Degradation of IGF-1 in the adult rat gastrointestinal tract is limited by a specific antiserum or the dietary protein casein. Journal of Endocrinology 146:215-225, 1995.