No. rBST stands for Recombinant Bovine Somatotropin hormone, which is a man-made version of the naturally occurring growth hormone BST found in dairy cows. This is a hormone that only affects cows and is not found in or becomes active in other species, including humans. A cow that receives rBST has no more BST hormone in her milk then a cow who has not received rBST. When properly used by a dairy farmer it can increase milk production by 10% and keeps cows healthier by assuring that they are metabolically active.
Unfortunately, the movement against using rBST was started when the dairy industry did not communicate the safety and benefits of this product in a timely and proper way to the consumer. At the same time, companies began exploiting consumer fears by using irresponsible absent-claim marketing tactics, thereby creating a very poor overall perception of rBST to the consumer.
It is unfortunate that this perception was created, as rBST is not only safe for cows and humans, it is an environmentally friendly safe-science tool. By using rBST, dairy cows and farmers would be able to produce the same amount of milk with 6% less land use and 10% fewer cows, there by offsetting the environmental impact (or carbon footprint) of a gallon of milk by 8% less than it is today. While the FDA (Food and Drug Administration), WHO (World Health Organization) and NIH (National Institutes of Health) have stated that milk from cows treated with rBST is safe to consume, the misperception that it is unsafe remains strong with consumers. This common misperception is the sole reason fairlife farmers do not treat their cows with rBST.