Recombinant bovine somatotropin (rBST) is a genetically engineered growth hormone, approved by the Food and Drug Administration (FDA) in the early 1990s for use in dairy cows. Biologically very similar to a hormone that cows naturally produce (bovine somatotropin, or BST), rBST is used by some commercial dairies to increase milk production. Cows injected with rBST every two weeks produce about 10 to 15 percent more milk than untreated cows.
The product was marketed as a way to make the dairy industry more efficient—and more profitable. But it’s debatable how successful rBST has been for either farmers or consumers.
The FDA asserts that milk from rBST-treated animals is safe and nutritious. Regulatory agencies in many other countries agree. But some countries, including Canada and those in the European Union, have banned rBST for various reasons.
The American Public Health Association, Oregon Physicians for Social Responsibility, the Humane Society and other health and animal rights groups are strong opponents. According to the Codex Alimentarius, which sets international food standards, no consensus has been reached on the safety of rBST for humans.
Issues and arguments
Animal welfare: The use of rBST makes cows more vulnerable to painful udder infections (mastitis). Lameness and reproductive problems have also been attributed to it.
Antibiotic resistance: When cows develop mastitis, they require antibiotics. Critics raise concerns that the antibiotics used to treat these additional infections contribute to bacterial resistance, which makes many antibiotics no longer effective against human infections.
But farm animals in the U.S. are already given large amounts of antibiotics, not only to prevent and treat illness but also to speed growth (up to 70 percent of all antibiotics used in the U.S. are administered to farm animals). The amount of antibiotics used to treat the increased cases of mastitis in rBST-treated cows is minuscule compared to what’s used in farm animals overall. Also, keep in mind that antibiotics are not allowed in milk—all milk is tested and if any residues are detected, the milk cannot be sold for human consumption.
Increased hormones in treated milk: All cow’s milk contains traces of BST—and, according to the FDA, there are no detectable differences in the amount of BST between milk from treated and untreated cows. But rBST stimulates production of another hormone, insulin growth factor (IGF-1). This has raised concerns because of associations between higher IGF-1 blood levels and some human cancers, including breast and prostate. Bovine IGF-1 is identical to human IGF-1 and has been found in slightly higher amounts in the milk from rBST-treated cows. The significance of this is unknown and much debated.
Environmental/economical issues: Proponents say rBST is environmentally friendly: producing the same amount of milk from fewer cows saves feed, water, and farmland and produces less manure and greenhouse gases. But there’s little evidence to confirm such benefits, besides one study coauthored by a Monsanto scientist. If there is any ecological benefit, it’s likely to be small. It’s also unclear whether rBST reduces milk prices or has been profitable for farmers.
Summing it up
Use of rBST in the U.S. has been declining. Only 17 percent of cows were treated in 2007, down from 22 percent in 2002, according to the latest United States Department of Agriculture (USDA) data. Though large dairy farms are much more likely to use the hormone than small farms, those numbers have declined, too.
If this trend continues, the issue of rBST may one day be moot. Meanwhile, there’s no compelling reason to consume milk (or other dairy foods) from cows treated with rBST, and at least one good reason to avoid these products—animal welfare. Though the evidence of harm to people is inconclusive, if you follow the “precautionary principle,” you can choose milk from untreated cows, especially if the milk doesn’t cost extra.
If you want to avoid products from rBST-treated cows, check the labels. Despite a long battle from industry, the FDA now allows milk from untreated cows to be labeled "rBST-free," as long as there’s a disclaimer, such as “The FDA has determined that no significant difference has been shown between milk derived from rBST-treated and non-rBST-treated cows.” Several companies including Dannon, Yoplait, Kraft and Starbucks, as well as some large retailers, have gone rBST-free. By law, USDA-certified organic milk cannot come from cows treated with hormones (or antibiotics).