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Dairy & Sexual Precocity

The effects of the hormones in cow’s milk on men and prepubescent children.

November 16, 2010 |
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Sources Cited



We’ve known for over a decade that women who eat meat have the highest levels of estrogenic hormones in their bloodstream, and vegans the lowest, but maybe that’s just because vegans are so much slimmer. This year, the consumption of animal products was definitively linked to the levels of circulating steroid hormones in the blood, regardless of body fat levels. The reason we’re concerned, is that the increased consumption of animal-derived food may have adverse effects on the development of hormone-dependent cancers. Among dietary risk factors, these investigators were most concern about milk and dairy productrs because the milk we drink today is produced from pregnant cows, in which estrogen and progesterone levels are markedly elevated. That may be why milk-drinkers have 5 times the rates of twins compared to vegans—that’s how much of an affect dairy can have on our hormones.
A landmark study was published this year in an international pediatrics journal on just how much estrogen we’re exposed to when we drink milk, given that the majority of commercial milk comes from pregnant cows. During the 60s and 70s, genetic manipulations of dairy cows enabled them to lactate throughout almost their entire pregnancies. That’s why commercial cow’s milk these days contains large amounts of estrogens and progesterone.
During the same period there’s been a dramatic increase in estrogen-dependent malignant diseases, such as ovarian cancer, uterine cancer, breast cancer, testicular cancer and prostate cancer. Eating and drinking estrogen is not just a problem for women; research shows that among various food items, cow’s milk and cheese had the highest correlation with the incidence and mortality rate of these male cancers as well.
Especially for prepubescent children, there is particular concern about exposure to exogenous estrogens in commercial milk produced from pregnant cows. So what they did is have young men, ages 19-21, and children, ages 7 through 9, try to chug a quart of cow’s milk in under 10 minutes.
This is what happened to the men. The levels of the pregnancy estrogen estrone started to shoot up 60% within an hour of drinking the milk. And their testosterone levels, significantly dropped. You know there are men who don’t want to drink soy milk because they have an irrational fear of phytoestrogens even though soy does not have feminizing effects on men, yet are perfectly willing to drink cows milk which has actual estrogen estrogens in it. Within one hour of the milk hitting their intestines estrogen levels go significantly up and testosterone levels go significantly down.
What about the children? Same thing, but even more dramatic, because they start out with such low levels. Within one hour of drinking cow milk, the level of sex steroid hormones in their little bodies more than triples. And half the kids couldn’t even finish the whole quart.
Why should we care? Because some of these powerful estrogens could be categorized as carcinogens, and milk is a rich source of these hormones, and concentrates in mammary drainage. Never seem to see that in the advertisements….
The corresponding suppression in testosterone secretion means that men are certainly affected by commercial cow’s milk. And height, growth, and sexual maturation of young children could also be affected by normal intake of cow’s milk. As I talked about in the last volume, recent surveys on the onset of puberty show an alarming trend of earlier sexual maturation in girls. During this same time period, exposure to exogenous—meaning external—estrogens through intake of commercial milk produced from pregnant cows has spread around the world. They think that this intake of pregnant cow’s milk is one of the major causes of early sexual maturation in young children. This relationship between estrogens in pregnant cow’s milk and sexual maturation in children must be acknowledged as an important theme.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by veganmontreal.

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Dr. Michael Greger

Doctor's Note

Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on dairy. Also, there are 1,686 other subjects covered in the rest of my videos--please feel free to explore them as well!

Please also check out my associated blog posts for some more context: Mad Cow California: Is the Milk Supply Safe?, Breast Cancer and DietCow's Milk Casomorphin, Crib Death, and AutismStool Size and Breast Cancer Risk,  Protecting Our Babies From PollutantsWhy Are Children Starting Puberty Earlier?, and Avoiding Dairy to Prevent Parkinson's

If you haven't yet, you can subscribe to my videos for free by clicking here.

  • Eric Needs

    great research

  • sagefemme

    Dr. Greger, are there studies about early puberty and non-milk dairy (yogurt, cheese, etc)? I assume there would be as much bovine endocrine debris in these products as the milk they were made from, but do we know?

    • Michael Greger M.D.

      The study showing the connection between premature puberty and animal protein consumption in general did indeed include all dairy items. More at

  • beedub8

    Hi Dr. Greger – My husband has prostate cancer and after two unsuccessful surgeries (brachytherapy and cryosurgery) he is now being given hormone treatments in a drug called Lupron. If prostate cancer is an estrogen-dependent disease, as you state in this video, why would the docs be feeding it to him to slow down the cancer growth?

    Here’s a partial definition of estrogen in the American Heritage Dictionary: “. . . substances that. . . are used to . . . ameliorate cancers of the breast and prostate.”

    What am I missing?

    Thank you so much for the excellent work you do!

  • psiscobr
  • Vallis

    Many people probably saw the story about Jeremy Pevin the actor where he said:


    “…”I was the guy that dabbled in soy milk, but now I’ve found out soy milk has enough estrogen for me to grow breasts,” he told STV (via Digital Spy). “I had to put the soy milk down. It was a very confusing time.”

    Turns out Piven was drinking 12 cups of soy milk a day! ….”

    Is it 100% conclusive that soy does not have unwanted estrogen for men? I have heard from more than one source that it was not good to drink too much of it if you are a guy.

    I do not drink regular cow’s milk (for decades) either and have switched to almond milk. I could not find any commentary on almond milk on this website.

    Perhaps you could direct me to a place where almond milk is mentioned on the site , if it is.

  • Lizzette Jimenez

    Is there any difference in the levels between a grass fed, pasture raised cow and that from a cow in a “Factory Farm” or “CAFO”? 

    • Toxins

       The only difference may be in contamination level but this is not the issue here. What this video is looking at is the nutritional composition of milk itself which is relatively unchanged whether it be organic or conventional. Milk is indeed used to grow a baby calf and this is a completely unnatural substance for adult humans to be consuming.

  • Michael Greger M.D.
  • Michael Greger M.D.

    Please also check out my associated blog post, Mad Cow California: Is the Milk Supply Safe?!

  • Kerem Avital

    Thank you for this interesting video (as usual) ,I’m a vegan dietitian and I have 2 question about this topic:
    1. I can’t remember where I read it, but I think that the half life of Estrogen is only 50 hours, I’m not sure if that’s correct and I also don’t know to what exactly does this Estrogen break up to… do you know about any research that deal with this question?
    2. About soy, I know that soy have a protective effect from Estrogen related cancer. But I’m not sure that this is the same with sexual development. most of the researches I found had been focus on infant formulas. And they found that soy formulas may also precede sexual development. I also found a research that claim that high Isoflavone in the serum may be connected to early puberty:'s your opinion about this subject?
    Sorry in advance for my bad grammar… (I’m from Israel)

  • Toxins

    jojo, the article is obsessed with phytic acid, when all beans, not just soy, and many grains contain phytic acid. Phytic acid is neutralized by cooking, and I do not know many people who eat raw beans. Trypsin is also deactivated with cooking. Soy does not affect hormonal levels either as shown by this video. Nitrosamines are forms not from high temperature cooking but when nitrites are exposed to fat. Nitrates and ntirites are different substances. Nitrates are found in plant products.

    The article is filled with flawed information.

    • Kathryn McMorrow

      What about eating raw legume sprouts? Is the phytic acid diminished at all through germination?

  • rob

    Does this also apply to fermented milk such as yogurt and kefir?

  • Skeptic

    This is one of the most helpful websites I’ve ever seen. I’ve been studying it for several months now and even down loading some of the journal articles it references. I feel so much better informed and able to take care of my family members better! Great work!

    • Thea

      Welcome aboard Skeptic. I agree that is feels great to be informed and self-empowered. This is a great site.

      Thanks for posting.

  • Elisabeth

    I’ve searched the (excellent and helpful) site for information about uterine/endometrial cancer but haven’t found much. Is there a lack of research to report? I’d love to be able to find more information.

    • Tommasina

      Elisabeth, is there something specific about uterine cancer that you’re looking for? I’ll see if I can help. :)