Growth Hormones in Milk

Ask the Pediatrician

A child drinking a glass of milk.
Can you even find milk that is made with synthetic growth hormones?. Photo by Thomas Northcut / Getty Images

Question. I am worried about the hormones in cow's milk. They might lead to early puberty in kids, right? Would it be safer to give my kids raw milk or organic milk instead?

Answer. Growth hormone can indeed be found in cow's milk.

Growth Hormone in Milk

While some of it is a synthetic recombinant bovine growth hormone (rBST) that is given to cows to help them make more milk, all cow's milk also contains a naturally occurring form of the same growth hormone.

Of course, it is the added growth hormone that some people are concerned about it.

It is important to keep in mind that whether natural or synthetic, most of these hormones are destroyed by pasteurization. Bovine growth hormone that survives pasteurization and also survives digestion, can't be absorbed by our intestines which only have receptors for human growth hormone.

Some parents are also worried about insulin-like growth factor-1 (IGF-1), which is increased in cows who receive synthetic recombinant bovine growth hormone. Although not destroyed by routine pasteurization, like bovine growth hormone, IGF-1 is not absorbed in our intestine. Even if it was, our own bodies naturally make much more IGF-1 each day than we could ever absorb in the milk we drink.

Concerns About Growth Hormones in Milk

While claims that growth hormones in milk are linked to early puberty (precocious puberty) in children seems to be a common worry of some parents, many studies have now debunked that theory.

Research now points to a rise in child obesity as a possible cause for some kids starting puberty at earlier ages.

Why blame growth hormones in milk? It was likely an easy thing to blame, as milk from rBST treated cows hit the market in the mid-1990s. That was shortly before some of the first studies showed that some kids were starting puberty a little earlier than they used to.

One problem with the theory is that growth hormone is not a steroid hormone like estrogen. It is a protein hormone that is mostly destroyed by pasteurization and digestion. Even kids who get daily injections of human growth hormone for short stature and other medical conditions don't start puberty early.

In addition to not causing early puberty, milk from cows that are treated with rBST are also not thought to increase a person's risk for breast cancer or prostate cancer.

More than the health of infants and children though, since studies have disproven most of those risks, some people are concerned about the health of cows that are treated with rBST. For example, these cows have a small risk of developing mastitis, which must be treated with antibiotics. Although these antibiotics don't end up in the milk, which is screened and tested, new voluntary rules from the FDA "to phase out the use of certain antibiotics for enhanced food production" might bring this issue into the spotlight.

While the effort to reduce the use of antibiotics to help reduce the development of antibiotic resistance is now focused on antibiotics that "are added to the animal feed or drinking water of cattle, hogs, poultry and other food-producing animals to help them gain weight faster or use less food to gain weight," will they turn to rBST treated cows next?

Avoiding Growth Hormones in Milk

Whatever you think about growth hormones in milk, it is now fairly easy to avoid them if you want.

Although approved for use in 1994, it has only been since 2008 following lawsuits from two separate dairy-producer trade organizations (International Dairy Foods Ass'n v. Boggs) that milk could be labeled as being free of synthetic growth hormone. Originally, the FDA did not require special labeling on milk from cow's treated with rBST because they stated that they did not have the authority to require such a food label since milk from treated and untreated cows was materially the same.

So people who want to avoid milk from cow's that are treated with synthetic growth hormone can:

  • buy milk that is labeled as being rBST-free, which is fairly easy, as it is available in most chain grocery stories, including CostCo, Kroger, Safeway, and Wal-mart, etc.
  • buy organic milk
  • buy a milk alternative that is fortified with vitamin D and calcium, such as soy milk, almond milk, hemp milk, or rice milk, etc.

If you simply avoid milk and go with other dairy products, including cheese, yogurt, and ice cream, keep in mind that unless they too are labeled rBST-free, then they could have been made with milk from cows treated with synthetic growth hormone. Like rBST-free milk though, it is easy to find other dairy products that are also rBST-free.

Are They Still Putting Growth Hormones in Milk?

Should you avoid milk from rBST cows?

Unfortunately, even as some studies contradict others about the harmful effects of rBST on cows, supporters tout that rBST treated herds need fewer resources to produce the same amount of milk, and the FDA has "concluded that consumption by infants and children of milk and edible products from rbGH-treated cows is safe," the decision about buying milk from rBST treated cows has likely been taken from you.

The hype about growth hormones in milk has likely not only removed it from store shelves, but may have had other effects.

How many parents have avoided cow's milk altogether because of unwarranted concerns about growth hormones in milk?

How many have switched to risky alternatives, such as raw milk?



FDA. Phasing Out Certain Antibiotic Use in Farm Animals. Dec. 11, 2013.

FDA. Report on the Food and Drug Administration's Review of the Safety of Recombinant Bovine Somatotropin. 04/23/2009. Accessed December 2013.

Moulton, Libby. Labeling Milk from Cows Not Treated with rBST: Legal in all 50 States as of September 29th, 2010. Columbia Science and Technology Law Review. Accessed December 2013.

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