What about the hormones in milk?
As a registered dietitian who specializes in nutrition education on behalf of Michigan dairy farmers, this is a question I’m often asked.
The short answer is that there are miniscule amounts of naturally-occurring hormones in cow’s milk, but the hormones do not affect human health.
To offer a detailed explanation from an expert who is not directly associated with the dairy industry, I called upon Michelle Kopcha, DVM, MS. Dr. Kopcha is a large animal veterinarian and associate professor in the department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University.
“Hormone can be a scary word,” says Dr. Kopcha. “But what are hormones? Hormones are proteins. Hormones are a good thing—they allow us to be alive. There are hormones in plants—such as in soy (and therefore soy beverage) and in cow’s milk.”
All multi-cellular organisms contain hormones, including plants and animals (such as cows).
What do hormones do? Hormones are chemical messengers. They are released by a cell or gland in order to send messages to other cells. “Hormones are produced in one place in an organism and have an effect in another place in that same organism,” explains Dr. Kopcha. “And many hormones are short lived. They do their job and then, after a few minutes, they’re changed into an inactive form.”
Both conventionally-produced and organic milk contain a very small amount of naturally-occurring hormones, however, there is no evidence that the hormones are harmful to health. “The hormones in milk are present in normal, acceptable levels,” says Dr. Kopcha.
There’s been some concern that the hormones in milk may cause early puberty in girls, however, science does not support a link between early puberty and milk or dairy products. According to a study published in the American Academy of Pediatrics’ journal, earlier onset of puberty in girls was associated with body fatness during childhood (Lee, et al., Weight status in young girls and the onset of puberty. Pediatrics 2007; 119: 624-630.)
Hormones are specific to the organism in which they are produced. “Cow hormones are not recognized by the human body,” says Dr. Kopcha. “As proteins, hormones in milk are broken down in the human digestive system. Because the hormones in milk are not active in the human body, they don’t have an effect on the human body.”
For more information:
Milk and Hormones Fact Sheet, DairyFarmingToday.org
Ensuring Dairy Food Quality & Safety From Farm to Fridge, Dairy Council Digest, Jan/Feb 2011
Organic Milk FAQ, DairyFarmingToday.org