Nearly a century ago, a contentious milk-making ingredient began its path toward commercial use.
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As food shortages persisted during World War II, scientists in Europe and the United States tried to ramp up milk production. Since the early 20th century, researchers had grown intrigued by a hormone from cows’ pituitary glands that supports growth. By injecting this hormone, known as somatotropin, into cows, they figured they could boost milk production.
But at the time, the amount of somatotropin they could extract from slaughtered cattle wasn’t enough to make a difference in the milk supply.
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This concept didn’t take off until the 1980s, when scientists took advantage of recent developments in genetic modification. They placed a gene that expresses somatotropin into bacteria, which can churn out an identical hormone known as recombinant bovine somatotropin (rbST) in large quantities. It’s also known as recombinant bovine growth hormone, but the industry didn’t want the public to associate this substance with the controversial steroidal hormones given to cows.
When rbST is injected into cows, it prompts the liver to generate Insulin-like Growth Factor (IGF-1), a protein hormone that stimulates milk production. Researchers claimed that this technique could deliver 10 to 25 percent more milk while lowering feed costs.
People had opposed genetically modified organisms in the U.S. since the 1970s, and surveys suggested that some concerned U.S. consumers would buy less milk if the government approved rbST.
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In 1993, rbST received FDA approval under the brand name Posilac from Monsanto**,** and it became commercially available the next year.
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Before rbST hit the market, some major grocery chains said they wouldn’t sell milk from cows treated with it. But ultimately, consumer demand for milk didn’t seem to take a significant hit in the following years.
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Around that time, regulators in other countries took a different opinion. In 1999, Canada and the European Union rejected the drug, both citing potential harms to cows. For example, they were concerned it could increase the risk of mastitis, or inflammation of the breast tissue, and infertility. New Zealand, Australia, and Japan have also banned its use.
As for possible risks to humans, the substance is broken down by enzymes in the gastrointestinal tract and isn’t absorbed intact, according to the FDA. The agency also points out that the hormone “does not promote biological activity in the human body.”
Some early studies found a possible connection between certain amounts of IGF-1 in people’s blood and some cancers, but more recent work indicates this relationship has limited evidence without clear conclusions. Another concern: Cows that develop mastitis from rbST require antibiotics, which might lead to antibiotic-resistance in people who consume their milk. But this also lacks solid evidence.
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Industry-sponsored research, along with reviews from the U.N. Food and Agriculture Organization and the World Health Organization, has failed to find real risks for people who drink or eat dairy from cows given rbST. But some U.S. public health organizations and many animal welfare organizations still have come out against it.
Over the past two decades, the dairy industry’s use of rbST has declined due to PR issues—along with emerging research showing that rbST doesn’t tend to meaningfully boost profits for many dairy farms. Usage of rbST peaked in 2002, when around 22 percent of U.S. cows received the hormone, a figure that fell to around 14 percent in 2014. By 2021, just around 1 percent of U.S. dairy farms were using rbST.
Meanwhile, Monsanto sold off its rbST product in 2008 to Eli Lilly amid “a recent surge in consumer opinion against its use,” leading major food chains to ditch milk from cows treated with it.
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While rbST doesn’t make a dent in today’s dairy supply, its rocky history shows that people’s discomfort with genetic modification can make a major impact in the grocery aisle.
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Lead image: Piece of Cake / Shutterstock
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