Hormones in Milk: Are They Causing Early Puberty in Girls?


06/01/2011

We’ve heard literally dozens of women discuss their concern with hormones in milk causing early puberty. In focus groups near Chicago and New York City, when we asked moms what concerns they have about today's food, the topic of early puberty due to "hormones in milk" came up several times. The women expressed that they know girls who have gotten their periods earlier than they thought was normal. News articles including The New York Times and The Huffington Post have discussed it. Foodie moms, farm moms and nannies are blogging about it.

Clearly, this is a scary scenario for parents – certainly one for which we wanted to help find some credible information. To get the facts, we enlisted the help of Dr. Ann Macrina, research/teaching associate, and Dr. Terry Etherton, animal nutrition professor, both of Pennsylvania State University.

BestFoodFacts: There seems to be growing concern about the association between hormones in dairy products and early puberty in girls. What are your thoughts on this concern?

Dr. Macrina: “The age at which puberty begins in girls has been decreasing since the mid-1800s. It is odd to blame it on dairy products since dairy consumption has actually decreased during the same timeframe. Several things have been cited as causing early puberty in girls:  

  • Girls are maturing more quickly because they have better nutrition.
  • Many believe girls must achieve a certain body mass for the onset of puberty to occur. The obesity rate is increasing in this country at a rapid rate and girls are reaching this point much sooner.
  • Ethnicity might play a role. African-American girls and girls of Hispanic heritage tend to reach puberty sooner than Caucasian girls."

“There are many contributing factors to be considered but I don’t think dairy consumption is one of them.”

Dr. Etherton: “There are zillions of protein hormones in both plant and animal foods. They are digested in the stomach, which kills their ability to have any biological activity. There is just no way to come to a science-based conclusion that hormones in food or dairy products cause early puberty.”

Hear Drs. Macrina and Etherton address the issue of early onset puberty in girls by clicking the audio link below.  

So what is causing early maturity in girls? Based on what Dr. Macrina indicated, it could be any of several factors – better nourishment, higher body weight and some even suggest exposure to chemicals. Here are a couple other sources citing possible reasons for early maturity:

Another question we heard come up wasn’t only specific to “normal” hormones – but synthetic ones. You know – the ones that equate to an extra label on your gallon of milk and a subsequent disclaimer label stating, "No significant difference has been shown between milk derived from rBST-treated and non-rBST-treated cows."

BestFoodFacts: We see terms like rBST associated with milk and it can be confusing, especially when retailers announce they won’t sell milk from cows treated with it. Please explain for us – what is rBST and why is it used?

Dr. Etherton: BST is a protein hormone that is naturally-occurring in cattle. It is also naturally in milk from cows. “The “r” means it’s been produced by recombinant (synthetic) technology. On farms, cows are treated with rBST to increase the amount of milk they produce. On a well-managed farm, cows treated with rBST will see a 10-to-15 percent increase in milk production.”

“It is important to understand that milk from cows already contains BST and treating cows with the recombinant version does nothing to increase the hormone levels in the milk. There is no difference between dairy products from cows treated with rBST and other dairy products.”

The U.S. Food and Drug Administration stands by the safety of rBST. In 1993, it was confirmed that milk from cows treated with rBST was safe for human consumption. In fact, the disclaimer language must be included on any such labeling nationwide because of an FDA ruling that says you can't insinuate there's anything wrong with a product like rBST.

BestFoodFacts: With all the available information, especially online, what are some good sources to trust when it comes to information on the effects of hormones in food animals?

Dr. Etherton:  “When consumers do a Google search they find many authentic looking websites that unfortunately contain a lot of misinformation. That creates challenges for people wanting to sort fact from fiction. I started a blog four years ago that addresses issues like food safety and the importance of using new technology so that we will be able to feed a rapidly growing global population.”

Dr. Macrina: “The Academy of Nutrition and Dietetics has a very nice web site for general nutrition information.”

To listen to our full interview with Dr. Macrina and Dr. Etherton, click the audio link below.   

Craving more food facts? Read on!

Consumer Question: Are hormones in my milk and meat making my kids bigger?

What could be causing early puberty in girls? Our expert clarifies a reader's question.

Does Milk Impact My Breast-Fed Baby?
View All Posts

Comments



Dr. Ann Macrina, via Best Food Facts - 06/06/2012

ASE: Thank you for your question. You bring up interesting points, and some clarification might help. There are two basic classes of hormones: protein hormones and steroid hormones. Protein hormones, like all proteins, are digested in the stomach after ingestion. They are broken down into amino acids and peptides, which are then absorbed from the small intestine into the body. The active hormone is not absorbed. Steroid hormones, like estrogen, are not digested in the stomach or small intestine, and they can be absorbed intact. One reason health care providers do not prescribe estrogen to breastfeeding women is that large doses can decrease milk production in the first two to three months of lactation. Reduced milk volume has been reported in some but not all studies. The potential effect on the infant is a slower growth rate due to reduced milk intake. It is not related to effects of estrogen on the baby. The transfer of estrogen into human milk is low, and the American Academy of Pediatrics considers its use compatible with breastfeeding. There are naturally occurring hormones in all foods, including breast milk. Plants like soybeans and cabbage have compounds with estrogenic activity. Meat and milk have small quantities of hormones, but at levels far lower than what humans produce in their own bodies on a daily basis. Administration of hormones to animals to improve milk production or growth rates has only a very small impact on the levels of hormones in meat and milk. It’s amazing that women will take birth control pills containing 20,000 to 30,000 ng of estradiol per dose but consider the 3 ng in a glass of whole milk or the 1.2 ng in a serving of beef from a steer that was given a growth promotant to be unsafe. A prepubertal girl produces 54,000 ng of estrogen per day, and an adult woman produces 630,000 ng per day. Boys and men produce amounts in between, and pregnant women produce 19,600,000 ng per day. Common sense tells us that the amounts of estrogens (and other hormones) in meat and milk are miniscule when you consider how much is produced by the human body every day.

ASE - 06/06/2012

So if hormones do not survive digestion, why wouldn't my Dr prescribe me estrogen while breastfeeding? If taking hormones affect my baby's body through my milk supply, then common sense says hormones in milk and food will affect us also. Hormones should not be added to our food supply period.

Joan - 05/17/2012

Early puberty runs in our family, my sister at 7 and me at 9. The only milk we drank came from my grandfather's cow who ate grass, hay and grain grown on the farm. My daughter, raised on milk from a white plastic jug from the store reached puberty at 11. I have an extremely hard time understanding how the panic mongers get their information. Genetics and good nourishment lead to earlier puberty in my opinion. The same people who pushed through laws forbidding raw milk are the same ones now screaming that our farmers are selling them unsafe milk. Are these the same folks who think the cows are being held in slavery and tortured by being hooked to milking machines giving our children plentiful, economical American grown food? Sheesh! Relax people, your vegan diet is shrinking your brain.

Jamie - 01/15/2012

I to believe that the facts are skewed. I believe that both the hormones injected in animals as well as the chemicals presented in the environment and used in hair treatments, oils all contribute to the onset early puberty. In addition, I feel the 100 pound weight argument can be tossed out the window..I see girls in the second grade who weight no more than 60 pounds developing breast buds and have mature b.o.

mark jacobson - 12/12/2011

Quote: "They are digested in the stomach, which kills their ability to have any biological activity." This doctor is a complete moron. Hormones in milk are designed by nature to survive digestion, because they are needed in the blood stream to promote the growth of infants! The hormones in cows milk are IDENTICAL to those found in mothers milk! They have to survive digestion to work!

Dr. Ann Macrina, via Best Food Facts - 12/02/2011

Dan - Exposure to chemicals and their effects on onset of puberty currently is a very active area of research. These chemicals include those found in pesticides (DDT, DDE, endosulfan, for example), or plastics used as food containers (BPA), and other plastics including those manufactured for flame retardance (BPP). This is by no means a complete list, but the concern is that these chemicals are structurally similar to estrogen. If they bind to the estrogen receptor in the body, these chemicals might mimic or block the actions of estrogen. Chemicals such as DDT were banned from use decades ago but are still present in the environment. Bisphenol A (BPA) has been shown to leach out of plastic containers especially with repeated use. However, it is difficult to quantify individual exposure to these chemicals and correlate that with outcomes like earlier age at puberty. Some researchers report earlier onset of puberty when animals are given high doses of these chemicals, but that is not the same as low-dose environmental exposure. Also, many of these chemicals have been in the environment since the 1960s, yet the age of puberty continues to decrease. A recent study examined girls who lived near or far from agricultural regions where pesticides were used. The scientists could not detect a difference in blood levels of the pesticide chemicals. In my original blog, I was referring to any chemicals that might mimic the actions of estrogen in the body. There are many conflicting studies, and it is not clear if the level to which people are exposed contributes to earlier onset of puberty. Based on the historical data before these chemicals were used, body weight consistently was around 100 pounds at the onset of puberty. The fact that it is still around 100 pounds implies that body weight has more of an influence on timing of puberty than typical exposure to these chemicals. However, it is important to understand how these chemicals act in the body, and research in this area continues.

Dan - 11/18/2011

"Dr. Macrina indicated, it could be any of several factors – better nourishment, higher body weight and some even suggest exposure to chemicals." Does Dr. Macrina mean chemicals like pesticides and herbicides?

MRL - 08/28/2011

So glad to see someone if finally explaining the science to those that do not understand! Our society is so quick to believe propoganda and people that are not experts in the area of food science. It is great to see the food industry taking this pro active approach. Thank you for putting this information out there!

Dr. Ann Macrina and Dr. Terry Etherton, via Best Food Facts - 08/08/2011

It is unfortunate that Rachel has elected to not believe the facts we presented. These are based on a vast scientific evidence base from scientists around the world. Hormone production does, indeed, control the onset of puberty in girls. In turn, hormone production is controlled by percentage of mature body weight, body fat, and ethnicity, in addition to numerous other factors. In the United States, the age at onset of puberty for girls was 14.75 years in 1877 and just under 13 years in the 1950s and 1960s. Today, the onset of puberty occurs, on average, at 12.1 years of age. Data collected since 1830 indicates that while the age of onset of puberty has decreased, the body weight at which it occurs is remarkably stable at around 106 pounds. It is not surprising that with the abundance of food available today and higher intakes, children will grow faster than in the past. Childhood overweight and obesity rates are increasing dramatically. Their prevalence is much higher than 20 years ago, and this contributes to the decreased age at onset of puberty. Even children who are not overweight will reach puberty sooner than in the past because they are growing faster. Fluid milk consumption by prepubertal and pubertal age children has declined since the mid 1970s. With the exception of a slight decline in the 1970s, total dairy product intake has remained relatively steady since the 1960s but is substantially lower than intake in 1940. In addition, the dairy products consumed today tend to be lower in fat than in the past. This is an important point, because the estrogens in milk largely associate with the fat fraction. Today’s high producing cows also produce less estrogen than cows in the past. Estrogen is the primary hormone that controls onset of puberty in girls. Based on the fact that milk consumption has declined and that lower fat dairy products are consumed today, intake of estrogens from dairy foods is lower today than in the past. So, it doesn’t make sense to blame dairy products for the earlier onset of puberty seen in girls today. It simply doesn’t add up.

rachel - 08/04/2011

i don't believe all the information in this article. I think the facts are skewed. There is a great milk lobby out there. Not all they say is true. Hormones are indeed causing younger girls to mature ahead of time. This is true for girls that are not even heavy. I have seen this with my own eyes.More than once.

NJR - 08/03/2011

I'm done with this site! Apparently anything the food industry decides to put in our food is "safe". Get your head out of your butt!

Suzyn - 06/30/2011

What a great resoucre this text is.