Verify: Do hormones in milk lead to early puberty?

It's a question we've heard for years, but do hormones in milk really cause early puberty? Our Verify team finds out.

I had no idea, but many parents are worried artificial hormones in milk lead to early puberty in girls.

I first heard about this from a good friend who told me about her concerns a few weeks ago. Her name is Joslyn Taylor.

“Yeah, hormones. That's what I care about. In the milk. Creeps me out,” Joslyn said.

She’s a mother of two daughters, and she's got a big problem with conventional milk because of artificial hormones.

So, I asked other moms I know. Many shared similar concerns. Plus, on the internet, I found lots of chatter on the topic.

“What I had heard is it could potentially start the puberty process in girls earlier,” Joslyn said.

Dairy cows have a natural growth hormone that helps them produce more milk. It’s called BST. In the 70's, scientists developed an artificial hormone, called rBST, that when injected into the cow, it helps them produce 10 to 15 percent more milk.

Do the hormones in milk cause early puberty in girls? I'm taking Joslyn to figure this out.

On the Farm

To see how a modern dairy produces milk, I'm taking Joslyn to the Southwest Regional Dairy Center in Stephenville, Texas. It's both a dairy and a research facility.

“I still picture a person sitting on a stool with a pail, milking a cow, even though I don't think that's happened for like 70 years,” Joslyn says, as our visit begins.

Actually, they're big on technology here. That’s what we’re learning from Ellisa Jimenez, a graduate student at Tarleton State University, who helps run the dairy. 

She’s showing a carousel parlor. It’s an elevated platform where the cows are milked.

“Mainly because it goes in a circular motion kind of like a merry-go-round or a carousel,” Ellisa said. 

The dairy tracks lots of data on these cows. They wear a collar that records how much they eat, how much they walk, how much milk they make.

“All that information gets sent to our database system. Gets filed into her cow record,” Ellisa said. 

One more piece of data is how much fat is in a cow's milk. For that, Joslyn and I are helping grab milk samples from the carousel.

“That's how we know what’s going on with them. Cows can’t really say, 'I'm feeling sick today. Give me some Tylenol,'” Ellisa said. 

What does Joslyn think about how the cows seem to be treated?

“I don't know if they're happy. I can't read the mind of a cow. I don't think they were in cow distress,” she’s saying.

What’s in the Milk?

Now that we know how a dairy works, let's get back to the question of artificial hormones and puberty.  Dr. Ellen Jordan is a professor and dairy specialist with Texas A&M University.

“Do you think the addition of hormones into feed and into the milk supply through feed is affecting our children through early onset puberty, or their development in any way?” Joslyn is asking Dr. Jordan.

“No, I don't,” Dr. Jordan says.  

Why would she say that? For 25-years, the FDA has said, milk from cows treated with artificial hormones is "safe for humans."  

And Dr. Jordan takes it one step further, she's pointing us to a widely-cited research paper in the Journal of the American Dietetic Association.

It compared milk from cows that were treated with artificial hormones to milk from cows that were not. It found artificial growth hormone "does not affect milk composition."

The 2008 report was funded by Monsanto, the company that first brought rBST to market.

“Are there are a lot of dairy farms in Texas that are adding it in?” Joslyn is asking Dr. Jordan.

“I don't know of any producers that are actually using it that are going to the fluid market in Texas, at all," Dr. Jordan said. 

Did you catch that?  

Dr. Jordan is saying Texas dairies do not treat their cows with hormones. She says consumers just don’t want artificial hormones and dairies stopped using them. So, artificial hormones are not even in the milk.

“It's all a marketing gimmick to get more money out of the consumer, is what it amounts to. I probably shouldn't have said that. But, you know, it is,” Dr. Jordan is saying.

“All those milks are safe. They've all basically got the same hormone levels in them. That's virtually non-existent compared to what the human produces themselves. It's not an issue,” Jordan finishes.

Now, Joslyn and I are back in the car, debriefing, after leaving the dairy. 

“Are you accepting of the argument that, if you're concerned about early puberty don't blame the milk?” I’m asking Joslyn.

“Well, I don't think we can blame the milk anymore because apparently, the hormone is in none of the milk unbeknownst to us,” Joslyn is saying.

Early Puberty

So, if you can't blame early puberty on the milk, what's really going on?  

We're at Children's Medical Center in Dallas talking to Dr. Grace Tannin, a pediatric endocrinologist.  She's telling us it is a fact that puberty is starting earlier. Breast development, in some girls, happens a year sooner than experts once thought.

“Body size and percentage of fat have a lot to do with the triggers for development,” she’s saying.

And there's research to back this up in the Journal of the American Academy of Pediatrics. It finds "earlier maturation" is happening. Tannin says it is likely a result of better overall nutrition.  

“Can milk, from cows, who've been treated with an artificial growth hormone cause them to start the development process earlier?” Joslyn is asking Dr. Tannin.

“I don't think there is any good evidence that actually happens,” Dr. Tannin answers.

Conclusion

So, Joslyn has learned a lot what's in milk, what's not and how it affects puberty. What’s her conclusion?

“I feel pretty comfortable that cows that have received an artificial growth hormone that milk, passed through to humans, is not doing anything to start the puberty process sooner,” she says.

“That has been, for me, verified,” she added.

So get out your Oreos, pour yourself a glass and enjoy because, we've verified, there's nothing to fear from hormones and milk. 

Don't take my word for it. Take hers.

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