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Do You Really Need to Worry About Hormones In Your Milk? Experts Weigh In.

June 16, 2023

There’s no shortage of food fear today, thanks to wild claims made daily about almost everything on grocery store shelves. Whether it’s pesticides, additives, sweeteners, or hormones, there’s always something to be worried about. Do you really need to be worried?  Most of these claims are based on opinion, not evidence.

When it comes to hormones in milk, we’ve heard it all. The myth that milk causes cancer, early puberty, and late menopause and can disrupt reproductive health has circulated for over a decade. We talked with experts and dove into the research to help you decide if you really need to worry about hormones in your milk.

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The truth about artificial growth hormones in milk

“When people ask about growth hormones in dairy cattle, they are often referring to rBST or recombinant bovine somatotropin, otherwise referred to as rBGH, recombinant bovine growth hormone,” says Lauren Twigge MCN, RDN, LD.

rBST is an FDA-approved synthetic hormone used to increase milk production in dairy cows. Hormones have never been added directly to milk but rather given to cows to help increase the milk they can produce.

While this artificial hormone is still considered safe to use, many farmers have stopped because of the public concern for human safety and the safety of cows treated with rBST. Cows treated with artificial growth hormones are at a higher risk of mastitis, a painful and severe udder infection requiring antibiotics for treatment.

Because of consumer demand, many farmers now focus on factors like better breeding, better nutrition, and improved overall care for the cows to naturally increase milk production without the need for growth hormones, explains Twigge.

Potential health risks of hormones in milk

You don’t have to worry about the rBST given to cows having a direct effect on you since the hormone is species-specific and not recognized in the human body, explains Twigge. There have been no differences found between milk treated with rBST and milk that has not been treated with the synthetic hormone, according to the Food and Drug Administration (FDA) and many other worldwide health organizations.

“Some naturally occurring hormones that can be found in a glass of milk included estrogen, progesterone, insulin-like growth factor-1, and others,” explains Twigge. It’s not just milk that gives us an extra dose of hormones, either. Soy, nuts, seeds, grains, meat, fish, and eggs all have hormones and hormone-like substances that we subsequently get through eating.

The main concern for human health is the possibility that hormones in milk increase insulin-like growth factor (IGF-1) in humans. A September 2020 study in Cancer Research found that high levels of IGF-1 in humans is connected to a higher risk of certain cancers, including thyroid, breast, prostate, and colorectal.

But drinking milk treated with rBST (or any milk for that matter) hasn’t been proven to cause an increase in IGF-1 in humans, as research has found inconsistent results. Some research has found that people who drink milk have around 10% more IGF-1 in their bodies, but the same increase was also found in people who drink soy milk, suggesting that the increase is not exclusive to milk hormones.

Other research has found that a 3-serving per day increase in milk produced an 18% increase in free IGF-1 but did not increase total IGF-1.  Keep in mind that three servings of dairy add 30 grams of protein to your diet, and diets high in protein have also been found to increase IGF-1.

As for early puberty? The research doesn’t support this myth. A large August 2015 study in the Journal of Nutrition followed over 5,000 girls from ages 9 to 14 and found that regular milk consumption did not predict or affect the age of menstruation.

Related: How Much Protein Do I Really Need? Here’s What Science Says.

Should we be worried about hormones from milk?

While the evidence doesn’t prove that there’s a difference between milk from cows treated with rBST and those that aren’t, choosing to avoid milk with artificial growth hormones is a personal choice that’s easy to make, as many farmers have stopped using this product. You can also buy organic dairy, as growth hormone is not allowed on cows producing organic milk.

Enjoying a glass of milk or eating other dairy foods is unlikely to cause any disruption in your own hormones, especially when included as part of a varied, overall healthful diet. Small amounts of hormones are found naturally in all sorts of plant and animal products, whose nutritional benefits far outweigh the potential concerns, especially considering how conflicting the research is to date.

Read next: 7 Best Drinks For Your Immune System, Say Experts

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