What Does Drinking Soy Milk Do to Hormone Levels?

The vast majority of breast cancers start out hormone-dependent, where estradiol, the primary human estrogen, “plays a crucial role in their breast cancer development and progression.” That’s one of the reasons why soy food consumption appears so protective against breast cancer: Soy phytoestrogens, like genistein, act as estrogen-blockers and block the binding of estrogens, such as estradiol, to breast cancer cells, as you can see at 0:24 in my video How to Block Breast Cancer’s Estrogen-Producing Enzymes.

Wait a second. The majority of breast cancers occur after menopause when the ovaries have stopped producing estrogen. What’s the point of eating estrogen-blockers if there’s no estrogen to block? It turns out that breast cancer tumors produce their own estrogen from scratch to fuel their own growth.

As you can see at 1:03 in my video, “estrogens may be formed in breast tumors by two pathways, namely the aromatase pathway and sulfatase pathway.” The breast cancer takes cholesterol and produces its own estrogen using either the aromatase enzyme or two hydroxysteroid dehydrogenase enzymes.

So, there are two ways to stop breast cancer. One is to use anti-estrogens—that is, estrogen-blockers—like the soy phytoestrogens or the anti-estrogen drug tamoxifen. “However, another way to block estradiol is by using anti-enzymes” to prevent the breast cancer from making all the estrogen in the first place. And, indeed, there are a variety of anti-aromatase drugs in current use. In fact, inhibiting the estrogen production has been shown to be more effective than just trying to block the effects of the estrogen, “suggesting that the inhibition of estrogen synthesis is clinically very important for the treatment of estrogen-dependent breast cancer.”

It turns out that soy phytoestrogens can do both.

Using ovary cells taken from women undergoing in vitro fertilization, soy phytoestrogens were found to reduce the expression of the aromatase enzyme. What about in breast cancer cells, though? This occurred in breast cancer cells, too, and not only was aromatase activity suppressed, but that of the other estrogen-producing enzyme, as well. But this was in a petri dish. Does soy also suppress estrogen production in people?

Well, as you can see at 2:34 in my video, circulating estrogen levels appear significantly lower in Japanese women than Caucasian American women, and Japan does have the highest per-capita soy food consumption, but you can’t know it’s the soy until you put it to the test. Japanese women were randomized to add soy milk to their diet or not for a few months. Estrogen levels successfully dropped about a quarter in the soy milk supplemented group. Interestingly, as you can see at 3:04 in my video, when the researchers tried the same experiment in men, they got similar results: a significant drop in female hormone levels, with no change in testosterone levels.

These results, though, are in Japanese men and women who were already consuming soy in their baseline diet. So, the study was really just looking at higher versus lower soy intake. What happens if you give soy milk to women in Texas? As you can see at 3:29 in my video, circulating estrogen levels were cut in half. Since increased estrogen levels are “markers for high risk for breast cancer,” the effectiveness of soy in reducing estrogen levels may help explain why Chinese and Japanese women have such low rates of breast cancer. What’s truly remarkable is that estrogen levels stayed down for a month or two even after the subjects stopped drinking soy milk, which suggests you don’t have to consume soy every day to have the cancer protective benefit.

Wait, soy protects against breast cancer? Yes, in study after study after study—and even in women at high risk. Watch my video BRCA Breast Cancer Genes and Soy for the full story.

 What about if you already have breast cancer? In that case, see Is Soy Healthy for Breast Cancer Survivors?

 And what about GMO soy? Get the facts in GMO Soy and Breast Cancer.

 Okay, then, Who Shouldn’t Eat Soy? Watch my video and find out.


What else can we do to decrease breast cancer risk? See:

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In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Are the BPA-Free Plastics Like Tritan Safe?

Do BPA-free plastics such as Tritan, have human hormone-disrupting effects? And what about BPS and BPF?

Recent human studies indicate that exposure to the plastics chemical BPA may be associated with infertility, miscarriage, premature delivery, reduced male sexual function, polycystic ovaries, altered thyroid and immune function, diabetes, heart disease, and more. Yet, “[a]s recently as March 2012, FDA stated that low levels of BPA in food are considered safe.” However, just months later, to its credit, the agency banned the use of BPA plastics in baby bottles and sippy cups. Regulators standing up to industry? Maybe I shouldn’t be so cynical! But, wait. The ban was at the behest of the plastics industry. It had already stopped using BPA in baby bottles so it was their idea to ban it.

The industry had switched from BPA to similar compounds like BPF and BPS. So, our diets now contain everything from BPA to BPZ, and the majority of us have these new chemicals in our bodies as well. Are they any safer?

As I discuss in my video Are the BPA-Free Alternatives Safe?, based on the similarities of their chemical structures, they are all predicted to affect testosterone production and estrogen receptor activity, as you can see at 1:40 in my video. However, they were only recently put to the test.

As you can see at 1:50 in my video, we’ve known BPA significantly suppresses testosterone production, and, from “the first report describing BPS and BPF adverse effects on physiologic function in humans,” we know those compounds do, too. Well, kind of. The experiments were performed on the testicles of aborted human fetuses. But, the bottom line is that BPS and BPF seem to have “antiandrogenic anti-male hormone effects that are similar to those of BPA.” So when you’re assured you shouldn’t worry because your sales slip is BPA-free, the thermal paper may just contain BPS instead. What’s more, BPS receipts may contain up to 40 percent more BPS than they would have contained BPA. So BPA-free could be even worse. In fact, all BPA-replacement products tested to date released “chemicals having reliably detectable EA,” estrogenic activity.

This includes Tritan, which is specifically marketed as being estrogen-activity-free. As you can see at 3:06 in my video, however, researchers dripped an extract of Tritan on human breast cancer cells in a petri dish, and it accelerated their growth. This estrogenic effect was successfully abolished by an estrogen blocker, reinforcing it was an estrogen effect. Now, the accelerated growth of the cancer cells from the Tritan extract occurred after the plastic was exposed to the stressed state of simulated sunlight. Only one out of three Tritan products showed estrogen activity in an unstressed state, for instance when they weren’t exposed to microwaving, heat, or UV rays. “Because there would be no value in trading one health hazard for another, we should urgently focus on the human health risk assessment of BPA substitutes.”

In the meanwhile, there are steps we can take to limit our exposure. We can reduce our use of polycarbonate plastics, which are usually labeled with recycle codes three or seven, and we can opt for fresh and frozen foods over canned goods, especially when it comes to tuna and condensed soups. Canned fruit consumption doesn’t seem to matter, but weekly canned vegetable consumption has been associated with increased BPA exposure. If you do use plastics, don’t microwave them, put them in the dishwasher, leave them in the sun or a hot car, or use once they’re scratched. But using glass, ceramic, or stainless steel containers is probably best.


For more on BPA, check out my videos:

Unfortunately, BPA isn’t the only plastics chemical that may have adverse health effects. See:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Pill-Free Ways to improve Your Sex Life

“Sex is important to health,” according to the Harvard Health Letter. “Frequent sexual intercourse is associated with reduced heart attack risk.” But, as I discuss in my video Do Men Who Have More Sex Live Longer?, that seems to be the perfect case of reverse causation. They’re implying that more sex leads to healthier arteries, but isn’t the opposite more likely—that is, healthier arteries lead to more sex? Blood flow in the penis is so reflective of blood flow elsewhere that penile Doppler ultrasound can predict cardiovascular disease. However, low frequency of sexual activity may predict cardiovascular disease in men independently of erectile dysfunction. This suggests that sex may be more than “just fun” and may also be therapeutic, or at least so says an editor of the Journal of Sexual Medicine and colleagues in discussing whether or not “frequent sexual activity can be prescribed” to improve general health. In men, they suggest it’s because more sex means more testosterone.

When men have sex, they get a big spike in testosterone levels in their blood, but, interestingly, in contrast, they don’t get a testosterone boost when they masturbate, as you can see at 1:21 in my video. This may be because “testosterone increases with competitive success,” like if you win a sports game. While sex “is not usually regarded as a competitive event…one’s mental state following coitus could nevertheless be something like that of a winner,” as opposed to the mental state after masturbation.

As you can see at 2:00 in my video, the spike in sex hormones in the blood is so great that men’s beards actually grow faster on days they have sex. And, since low testosterone levels are associated with increased risk of mortality, this could help explain the health benefits of having sex.

So, do men who have more sex actually live longer? I searched Pubmed for sexual activity and longevity and found a study supported by the U.S. Department of Agriculture, titled “Sexual activity and longevity of the southern green stink bug”—clearly an example of our taxpayer dollars hard at work. I was less interested in whether or not screwworms live up to their namesake and more interested in a study on sex and death, in which the objective was “to examine the relation between frequency of orgasm and mortality.” The researchers found that men with “high orgasmic frequency” appeared to cut their risk of premature death in half and, apparently, the more, the better: There was an associated 36 percent drop in mortality odds for every additional 100 orgasms a year. “Conclusion: Sexual activity seems to have a protective effect on men’s health”—but, apparently, not if you cheat. “Unfaithfulness in men seems to be associated with a higher risk of major cardiovascular events,” like heart attacks and strokes. “Extramarital sex may be hazardous and stressful because the lover is often younger…[and] a secret sexual encounter” may be more stressful.

In a large autopsy series, the majority of cases of sudden death during sex occurred in men during extramarital intercourse. The absolute risk is low—“only one out of 580 men might be expected to suffer a sudden death attributable to sexual intercourse”—but for those at high risk, research shows that “[s]ex in familiar surroundings, in a comfortable room temperature, and with the usual partner adds less stress to the heart” and may be safer.

Speaking of safe sex, you thought drinking and driving was bad? “While it is generally assumed that sexual behavior happens in parked cars, there is little discussion…in the research literature of sexual activity in moving vehicles.” About one in five college students report engaging in sex while driving, nearly half while going more than 60 miles an hour. Researchers suggest maybe this is something students should be warned about in health class.

When done right, though, love may protect your lover’s life. Given the benefits of sexual activity, “intervention programmes could also be considered, perhaps based on the exciting ‘At least five a day’ campaign aimed at increasing fruit and vegetable consumption—although the numerical imperative may have to be adjusted.”

What are some pill-free ways to improve your sex life? Exercising, quitting smoking, not drinking too much alcohol, not weighing too much, and eating a healthy diet. But what does it mean to “eat a healthy diet”? As I discuss in my video Best Foods to Improve Sexual Function, heart-healthy lifestyle changes are sex-healthy lifestyle changes, which have been demonstrated in studies from around the world, including in women. “Sexual function in women is significantly affected” by coronary artery disease, atherosclerotic narrowing of blood flow through our arteries, including the arteries that supply our pelvis. So, high cholesterol may mean “lower arousal, orgasm, lubrication, and satisfaction,” and the same holds for high blood pressure.

Given this, putting women on a more plant-based diet may help with sexual functioning.   Researchers found that improvements in female sexual function index scores were related to an increased intake of fruits, vegetables, nuts, and beans, and a shift from animal to plant sources of fat. The same for men: a significant improvement in international Index of Erectile Function scores. In fact, the largest study on diet and erectile dysfunction found that each additional daily serving of fruits or vegetables may reduce the risk of ED by 10 percent. But why? It may be due to the anti-inflammatory effects. Two years on a healthier diet resulted in a significant reduction in systemic inflammation, as indicated by reduced levels of C-reactive protein. Fiber itself may play an anti-inflammatory role. Those who eat the most fiber tend to have significantly lower levels of inflammation in their bodies, as you can see at 2:06 in my video. The opposite was found for saturated fat, “associated with an increased likelihood of elevated CRP”, C-reactive protein levels.

We’re used to seeing changes in inflammatory markers over weeks, months, or years, but people don’t realize that the level of inflammation in our bodies can change after only a single meal. For example, there’s a pro-inflammatory signaling molecule in our bodies called interleukin 18, thought to play a role in destabilizing atherosclerotic plaque. As such, the level of interleukin 18 in the blood “ is a strong predictor” of cardiovascular death.

What would happen if you fed people one of three different types of meals: sausage-egg-butter-oil sandwiches, cheeseless pizza with white flour crust, or the same cheeseless pizza but with whole-wheat crust? Within hours of eating the sausage sandwich, interleukin 18 levels shot up about 20 percent, an effect not seen after eating the plant-based pizza. In contrast, those eating the whole food, plant-based pizza made with the whole-wheat crust had about a 20 percent drop in interleukin 18 levels within hours of consumption, reinforcing dietary recommendations to eat a diet high in fiber and starches, and low in saturated fat to prevent chronic diseases.

But the billions in profits are in pills, not plants, which is why the pharmacology of the female orgasm has been studied ever since 1972 when a researcher at Tulane University implanted tubes deep within the brain of a woman so he could inject drugs directly into her brain and was able to induce repetitive orgasms. A man who had electrodes placed into similar parts of his brain was given a device for a few hours that allowed him to press the button himself to stimulate the electrode. He pressed the button up to 1,500 times.


For more on male reproductive health, see:

Also check out my other men’s health videos, such as:

What effect might that inflammation directly following an unhealthy meal have on our artery function? Check out my three-part endotoxins series starting with The Leaky Gut Theory of Why Animal Products Cause Inflammation.

And why exactly is fiber anti-inflammatory? Watch my video Prebiotics: Tending Our Inner Garden.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: