Does the estrogen in cow’s milk promote the growth of hormone-sensitive cancers or cause early puberty in children? Nutrition Diva investigates.
The amount of hormones in milk is tiny compared to what’s already in your body. Guys, your bodies produce about 6,000 times as much estrogen every day as you’d get in a glass of whole milk. Ladies, your bodies are producing 28,000 times that much. Compared to what your own body pumps out, the amount of estrogen you’re exposed to from dairy products is far too little to have any physiological effect.
If drinking milk could raise your estrogen levels, we could expect it to be useful in treating symptoms of menopause. Ironically, soymilk may be more effective than cow’s milk in beating hot flashes.
There’s no clear link between intake of dairy products and early puberty. It’s true that kids are reaching puberty earlier these days but I don’t think dairy is the cause. For one thing, kids are drinking less milk than they used to. If the hormones in dairy caused early puberty, we’d expect to see the average age of puberty go up as dairy consumption went down, but the opposite is true. I think the increase in childhood obesity is a much more likely explanation for early puberty because circulating estrogen levels increase with body fat.
There’s no clear link between intake of dairy products and increased risk of breast or ovarian cancer. Some people have pointed out that breast cancer rates are lower in cultures or countries where dairy is not commonly consumed. But there are so many other differences between these populations that it’s impossible to say that the difference in cancer risk—or any other difference, for that matter—is due to the difference in dairy intake.
When we compare people from the same country and culture, those who drink the most milk don’t have a higher incidence of breast cancer than those who drink the least. In fact, several studies have found a modest protective effect.
See also: Does Dairy Cause Breast Cancer?
There may be a link between dairy intake and prostate cancer. Prostate cancer is also a hormone related cancer, of course, and studies have found that men who consume more than four servings of dairy a day have a slightly elevated risk of this common disease. It's not clear whether this is due to a hormonal effect or something else. But the fact that dairy doesn't seem to affect breast cancer risk or puberty rates suggests that the hormones in milk may not be the most likely explanation. It's even possible that the link between dairy intake and prostate cancer is purely coincidental.
See also: Does Dairy Raise Your IGF-1 Levels?
How Much Dairy Should You Eat?
If you choose to consume dairy products, I think it makes sense to aim for no more than 3 servings a day
If you choose to consume dairy products, I think it makes sense to aim for no more than 3 servings a day—especially if you choose whole milk and other full-fat dairy products. Three servings of dairy a day is enough to meet your daily requirement for calcium (without overdoing it) and it keeps you well within the recommended amount of saturated fat.
See also: How Much Dairy Is Too Much?
If you choose not to consume dairy products, there are plenty of other ways to get your calcium.
See also: What Are the Best Sources of Calcium?
Do You Do Dairy?
I'd love to hear from you about whether or not you eat dairy products, and why. Post your comments and questions below or on the Nutrition Diva Facebook Page. See also below for several related articles you may find interesting.