Transcript: Dairy & Sexual Precocity
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
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 concerned about milk and dairy products, 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 five times the rates of twins compared to vegans—that’s how much of an effect 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 through 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 they’re perfectly willing to drink cow’s 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’s 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.
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