We asked 3 scientists to each answer this question:
Scientist #1: Dr. Dale Bauman, Ph.D. is Liberty Hyde Bailey Professor Emeritus in the Department of Animal Science and the Division of Nutritional Sciences at Cornell University. His research on metabolic regulation of nutrient use has led to development of new technologies and commercial practices, including recombinant bovine somatotropin hormone. Dr. Bauman was elected to the National Academy of Sciences. He served on various USDA Advisory Committees, and was President of the American Society for Nutrition.
I’d specifically like to tackle the first part of this question, and explain what recombinant bovine somatotropin (rbST)—also called recombinant bovine growth hormone (RBGH)—is. At the most basic level, Bovine Somatotropin (bST) is a protein hormone produced in the pituitary gland of a cow’s brain. bST is responsible for the regulation of milk production in lactating dairy cows. This occurs through coordination of the cow’s metabolism, such that the nutrients she consumes through her feed are efficiently used to produce milk.
Recombinant-DNA technology has allowed for the commercial production of bST, known as rbST. What results is a biologic equivalent to the natural, pituitary-derived bST. It is of value to note that because of this equivalence, there is no test that can identify if the milk did or did not come from cows supplemented with rbST. As a result, instead of a label identifying “rbST-free” milk, the FDA has required the label to include the disclaimer statement that, “No significant difference has been shown between milk derived from rbST-treated and non-rbST-treated cows.”
Among one of the first proteins produced through biotechnology application, rbST has been marketed for 28 years (24, United States). As of 2014, more than 35 million dairy cows have received rbST supplementation, representing a supply of over 80 billion gallons of milk. rBST’s contribution to improving productive dairy cow efficiency (milk output/resource input) is one reason that today’s carbon footprint per gallon of milk production is only one-third of that in the 1940s.
Additional information can be found here.
Scientist #2: Dr. Alice Callahan earned a B.S. in Animal Science from Cornell University and Ph.D. in Nutrition from the University of California, Davis. She writes about science, nutrition, and parenting on her blog, Science of Mom, and in her first book, to be published by Johns Hopkins University Press in 2015.
With every trip to the grocery store, we are confronted with a dizzying array of food choices. We may have different priorities as we approach these decisions, but we all agree that we want our food to be safe. In the dairy case, some products are labeled as being from farms that pledge not to use recombinant bovine somatotropin (rbST). The use of rbST has proven to be controversial, but scientific evidence is reassuring that it doesn't compromise the healthfulness or safety of dairy products.
From a nutrition standpoint, studies show that the use of rbST doesn't change the nutrient composition of milk. All milk is a valuable source of calcium, vitamin D, potassium, high-quality protein, and many other nutrients. A common safety concern about rbST is that it might alter the concentrations of hormones in milk, particularly somatotropin, also called growth hormone, and another hormone called IGF-I.
There are several reasons why we don't need to worry about growth hormone in milk, regardless of the use of rbST. First, rbST treatment doesn't actually increase growth hormone in milk. Second, growth hormone is a protein, and like all food proteins, it is broken down in the human digestive system. (This is why diabetics have to inject insulin; if they drank it, it would have no effect.) Finally, growth hormone is species-specific, so bovine growth hormone doesn't have biological activity in the human body.
Growth hormone also stimulates the production of another hormone called IGF-I. This is of greater concern because the human and bovine versions are identical, making bovine IGF-I potentially biologically active in humans. The use of rbST in cows can cause a small increase in IGF-I in milk, although concentrations are still within a normal range for cow's milk and human breast milk. Most IGF-I in milk seems to be broken down by the human digestive system, but small amounts may be absorbed. However, this amount would be tiny compared to natural production of IGF-I by the human body. It has been estimated that the increase in IGF-I in milk from cows treated with rbST would be less than 0.09% of daily human production of the hormone (and that's assuming that a person drank 1.5 L of milk per day, all from cows treated with rbST, and absorbed all the IGF-I in it). Despite many studies, there is no evidence for a link between IGF-I in milk and cancer or diabetes.
Food labels can be overwhelming, but science can help us understand what they do and don't mean. In the case of rbST, national and international food safety organizations periodically review this evidence and agree that milk from cows treated with rbST is safe to drink.
Scientist #3: Joanna Lidback is a first-generation dairy farmer (45-cows) in northeast Vermont, as well as a mother of two. In addition to being an active partner on the farm, she works full-time with Farm Credit, and as vice president of her county Farm Bureau. In July, she was called on to testify before the House Agriculture Committee hearing on he Societal Benefits of Agricultural Biotechnology. She holds a bachelor’s degree from Cornell University, and an MBA.
Recombinant bovine somatotropin (rBST) is a tool to increase a cow’s milk production. We would give it to a cow if her milk production was lagging for whatever reason – perhaps she had been injured or sick and upon return to good health, we could help her get back to her normal production levels with rBST. Another way to use rBST would be to administer it to all or most cows on a regular basis in order to boost production across the whole herd. While many see the use of rBST as an example of “big agriculture” practices in a negative way, the reality is that is can be used by all sizes of farms. In particular, its use could help small or resource-limited farms boost their production in a way that does not harm the cow, makes better use of existing resources and does not require expanding the actual herd size by number of cows including additional capital investment and other costs of business growth, (i.e., greater inputs, labor challenges and regulatory issues).
Our milk cooperative has asked us to not use it anymore. This way, our milk is more marketable to processors who may want to use a label on their end product that reads “made from cows not treated with rBST.” This label, driven by the marketplace, does not convey anything about the safety of the product but rather production methods. Consumers, not understanding the science behind rBST and being driven by fear stirred up by anti-agriculture activists, rejected this technology for no sound reason. It has no adverse effect on human health. Milk that is from cows treated with rBST is just as safe as that from those that are not. At the end of the day, compositionally, milk is milk; there is no significant difference between the level of hormones found in milk based upon production methods – either using rBST or not, and that includes organic milk as well.