Bovine growth hormone occurs naturally in dairy cows and is present in all raw milk. However, a synthetic form of this hormone called rBGH or recombinant bovine growth hormone has been produced by a company that manufactures herbicides and genetically modified seeds. Many modern dairy cows receive rBGH injections which artificially increases their milk production by 10-15 percent (1).
Despite the objection of consumer and health advocacy groups such as the Consumers Union and Cancer Prevention Coalition, the Food and Drug Administration approved the use of rBGH in 1993 stating that the residue levels of these hormones in food have been demonstrated to be safe. Critics point out that rBGH has not been properly tested in humans for long term effects. The FDA’s approval was based on a single study funded by the company that manufactures rBGH and tested the effects of the additive on just 30 rats over a 90 day period.
The main function of rBGH is to increase the milk yield of dairy cows. However, it has many harmful side effects that affect the cows’ overall health. For example, cows that receive rBGH injections experience higher rates of mastitis, an infection of the udder that leads to swelling and inflammation. Not only is this painful for the dairy cow, it forces dairy farmers to rely on antibiotics to treat these infections.
Also, because it is a potent hormone that can disrupt normal fetal calf development, rBGH has been shown to lead to an increased incidence of birth disorders. Since the introduction of rBGH injections in the dairy industry, the number of calves born with birth defects to dairy cows has increased significantly.
Forcing dairy cows to produce more milk than is natural also puts tremendous strain on their bodies. Not only does it take a lot of energy to produce milk, but most of the cows’ nutrients go into the milk (since by design milk is produced to nourish baby calves). As a result, many cows become malnourished as they are losing more energy and nutrients than they can consume in their feed.
Other side effects of rBGH include hoof problems, increased pus in milk, heat stress, diarrhea and other gastrointestinal problems.
The use of rBGH not only results in health problems for the cows, it may also be harmful to humans who consume their milk.
A significant body of scientific data has linked rBGH to possible increases in cancer and antibiotic resistance in humans. The injection of rBGH in cows elevates another powerful growth hormone called IGF-1. This hormone has been identified in numerous studies to increase breast, prostate, colon, lung and other cancers in humans. Scientific studies suggest that IGF-1 survives pasteurization as well as digestion and enters the bloodstream in sufficient quantities to potentially trigger increased cancer rates (2).
As previously mentioned, there has not been a thorough study examining the long term effects of rBGH in humans. However, both
Canada and the European Union have taken a precautionary approach and banned the use of rBGH in their dairy cows.
Note: The FDA has said no significant difference has been shown and no test can now distinguish between milk from rBGH treated and untreated cows.
1. Webb, D.W., “Artificial Insemination in Dairy Cattle.”
Florida IFAS Extension, June 2003. Accessed March 10, 2007.
2. The Scientific Committee on Veterinary Measures Relating to Public Health. “Assessment of Potential Risks to Human Health from Hormone Residues in Bovine Meat and Meat Products.” European Commission, April 30, 1999. Accessed March 20, 2007.