There are lots of things we want to do in life. Climb a mountain, write a song, watch our grandchildren grow up. But guess what? We can’t do any of those things if we don’t have our health.
Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger. And I’m here to bring you evidence-based research that takes the mystery out of the best way to live a healthier, longer life.
On the show today we look at how the consumption of animal products may cause an increase of the hormone, IGF-1, which may increase both cancer risk and cancer progression.
First up, how the implantation of hormones into U.S. beef cattle may have adverse human health effects.
Last year, Japanese researchers were lamenting the dramatic increase in hormone-dependent cancers in their country; four times more breast and ovarian cancer; eight times more endometrial cancer; and ten times more prostate cancer, just in the last 25 years. They suspect it might be because they import so much hormone-laden beef from the United States. But just because we implant cattle with hormones doesn’t mean it actually makes it into the meat.
We inject these hormone implants into the ears of cattle, but the ears get chopped off at slaughter, so the U.S. beef industry argues that the hormones don’t get into the meat. But these researchers were suspicious, so they compared the hormone levels in American beef to Japanese beef, where they don’t commonly inject cattle with hormones.
They found up to 600 times the level of estrogens in American beef. So they got the feeling that the increasing consumption of estrogen-rich beef following steroid implantation might facilitate estrogen accumulation in the human body, and could be related to the incidence of hormone-dependent cancers, although further studies are required. For example, eggs may be the greatest source of estrogens in a person’s “normal” diet.
Why would estrogen-rich beef lead to prostate cancer? You think of that more related to male hormones, like testosterone. We inject cattle with that, too. Just like athletes can use doping agents in sports to build up their muscles, in the livestock industry, anabolic steroids are given to cattle to “beef” up their muscles. We don’t just give estrogens; we implant anabolic male steroids with brand names like “Magnum” and “STEER—oid”—some of which contain androgens like testosterone.
Where are these hormones found the most? Researchers in Iran last year compared the levels of testosterone in the meat, liver, and testicles of sheep. What did they find? Interestingly, though testicles produce testosterone, they don’t store it, and so it builds up elsewhere in the body. In fact, the levels of anabolic steroids in meat can be so high that studies have shown that athletes who eat certain kinds of meat can be falsely accused of abusing steroids.
As with dairy, eating meat may also affect prepubescent children, boosting their production of male sex hormones in both boys and girls, which may hasten the first appearance of pubic hair between ages six and eight. Even though the effect was small, the fact that it’s a modifiable factor, something you can change about your child’s diet, makes it potentially relevant.
In our next story, we look at how consumption of cow’s milk can upset our body’s hormonal balance.
So, where do we go from here? Here’s what the science says: “Our deeply-rooted beliefs about the wholesomeness of milk and dairy products should be reconsidered. We are just beginning to re-assess the biological effects of milk and dairy products as human foodstuffs. Human beings are the only species on earth that from the beginning of infancy into adulthood are subjected to this external hormonal manipulation. Milk developed over the course of mammalian evolution only to be consumed during infancy. The consumption of cow’s milk in humans interferes with the sensitive endocrine regulatory network from the fetal period into old age.”
While dairy is being re-evaluated as human food, in the very least, “given the tumor promoting effect of IGF-1 insulin-like growth factor 1, from dairy, patients with tumorous disease should restrict consumption of milk and milk protein.” Unfortunately, we don’t know if we have a tumor until it gets big enough to be picked up. “The same applies to patients with coronary heart disease the #1 killer in the United States and those with a family history of neurodegenerative disease. Milk has already been identified as an aggravating factor in the acne epidemic but it is even more important that excessive milk consumption can promote diseases commonly associated with a Western lifestyle.”
Finally today, we ask If the synthetic estrogen BPA is linked to billions of dollars’ worth of medical problems a year, why is it still allowed in the food supply?
“The number of new chemicals is increasing exponentially.” We’re talking 12,000 new substances a day. Yet, data aren’t available on the hazards of even some of the high volume chemicals. BPA is one of the highest volume chemicals, with billions of pounds produced each year. And, studies have “raised concerns about its possible implication in the cause of certain chronic diseases, such as diabetes, obesity, reproductive disorders, cardiovascular diseases, birth defects, chronic respiratory and kidney diseases and breast cancer.”
A new study on the health implications of BPA comes out nearly every week. BPA was first developed over a hundred years ago as a synthetic estrogen. But it wasn’t until the 1950s that industry realized it could be used to make polycarbonate plastic, and it rapidly became one of the most used chemicals worldwide, even though it was recognized to have hormonal effects. About a billion pounds are also used to line food and beverage cans; especially, it seems, in tuna and condensed soups.
And now, we basically all have BPA in our bodies, and our children’s bodies. But, not to worry; the government says up to 50 a day is safe; 50 micrograms per kilogram. And, even those working in Chinese BPA factories don’t get exposed to more than like 70 times lower than that safety limit. Okay, then, why did exposure seem to affect the male workers’ sperm counts?
In the U.S., the general population only gets less than like a thousand times lower than the safety limit. Yet, still, we seem to be seeing adverse effects on thyroid function, weight control, blood sugar control, cardiovascular disease, liver function, and immune function even at those incredibly low doses. So, “the fact that there are significant adverse effects in populations exposed to BPA at concentrations thousands of times lower than the official tolerable daily limit indicates that the safe exposure to BPA may be much lower than previously thought in humans.” Yet, the limit hasn’t been changed. It’s been banned from baby bottles and sippy cups, but nearly unlimited doses are still apparently okay for everyone else. What’s the disconnect here?
It has to do with the fascinating world of low-dose effects of hormone-disrupting chemicals. “For decades, these chemicals “have challenged traditional concepts in toxicology”, particularly the old adage that it’s the dose that makes the poison, the concept “that lower exposures to a hazardous compound will, therefore, always generate lower risks.” That’s “the core assumption underlying our system of chemical-safety testing.” They start dosing lab animals with super high amounts, and then keep lowering the dose until whatever adverse effects disappear; then, add a safety buffer and assume everything below that dose should be okay, assuming the curve looks like the higher the dose, the higher the effect. But, hormone-disrupting chemicals can have all sorts of “curious curves.” Basically, how could something have more of an effect at a lower dose?
Think about a hormone, and its receptors in the body. At low levels of the hormone, like going from 0 to 1, the receptors can fill up quickly. But, once they’re almost all filled up, going from 4 to 5, adding really high doses may not change things much. Let’s use an actual BPA example. This was a study to see if BPA suppressed an obesity-protective hormone in fat samples taken from breast reduction and tummy tuck patients. At a hundred nanomoles of BPA hormone levels are no lower than they are at 0 BPA. And, since most people have levels like between 1 and 20, then BPA must be safe. But, the actual graph, no suppression at 0; no suppression at 100. But, right where levels are in people’s bodies, BPA appears to cut hormone release nearly in half.
As the world’s oldest, largest, and most active organization devoted to research on hormones concluded, “even infinitesimally low doses of exposure; indeed, any level of exposure at all may cause problems,” nearly three billion dollars’ worth of problems every year, just counting the estimated effects of BPA on childhood obesity and heart disease alone.
Now, there are alternatives that the industry could use; the problem, though, is that they may cost two cents more.
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Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.