The Difference Between Alpha and Beta Receptors Explain Soy’s Benefits

“[S]oyfoods have become controversial in recent years…even among health professionals…exacerbated by misinformation found on the Internet.” Chief among the misconceptions is that soy foods promote breast cancer because they contain a class of phytoestrogen compounds called isoflavones, as I explore in my video, Is Soy Healthy for Breast Cancer Survivors? Since estrogens can promote breast cancer growth, it is natural to assume that phytoestrogens might, too, but most people do not realize there are two different types of estrogen receptors in the body, alpha and beta. Unlike actual estrogen, soy phytoestrogens “preferentially bind to and activate ERβ,” estrogen receptor beta. “This distinction is important because the [two types of receptors] have different tissue distributions within the body and often function differently, and sometimes in opposite ways. This appears to be the case in the breast,” where beta activation has an anti-estrogenic effect, inhibiting the growth-promoting effects of actual estrogen—something we’ve known for more than ten years.

The effects of estradiol, the primary human estrogen, on breast cells are “completely opposite” to those of soy phytoestrogens, which have “antiproliferative effects on breast cancer cells…even at [the] low concentrations” we get in our bloodstream after eating just a few servings of soy. This makes sense, given that after eating a cup of soybeans, the levels in our blood cause significant beta receptor activation, as you can see at 1:27 in my video.

Where did this outdated notion that soy could increase breast cancer risk come from? The concern was based largely on research that showed that the main soy phytoestrogen, genistein, stimulates the growth of mammary tumors in a type of mouse—but, it turns out, we’re not mice. We metabolize soy isoflavones very differently from rodents. As you can see at 2:00 in my video, the same soy phytoestrogens led to 20 to 150 times higher levels in the bloodstream of rodents. The breast cancer mouse in question had 58 times higher levels. What does this mean for us? If we ate 58 cups of soybeans a day, we could get some significant alpha activation, too, but, thankfully, we’re not hairless athymic ovariectomized mice and we don’t tend to eat 58 cups of soybeans a day.

At just a few servings of soy a day, with the excess beta activation, we would assume soy would actively help prevent breast cancer. And, indeed, “[s]oy intake during childhood, adolescence, and adult life were each associated with a decreased risk of breast cancer.” Those women who ate the most soy in their youth appeared to grow up to have less than half the risk. This may help explain why breast cancer rates are so much higher in the United States than in Asia, where soy foods are more commonly consumed. Yet, when Asians come to the United States and start eating and living like Americans, their breast cancer risk shoots right up. Women in their 50s living in Connecticut, for example, are way at the top of the breast cancer risk heap, as you can see at 3:00 in my video, and have approximately ten times more breast cancer than women in their 50s living in Japan. It isn’t genetic, however. When Japanese women move to the United States, their breast cancer rates go up generation after generation as they assimilate into American culture.

Are the anti-estrogenic effects of soy foods enough to actually change the course of the disease? We didn’t know until the first human study on soy food intake and breast cancer survival was published in 2009 in the Journal of the American Medical Association, suggesting that “[a]mong women with breast cancer, soy food consumption was significantly associated with decreased risk of death and [breast cancer] recurrence.” That study was followed by another study, and then another, each with similar findings. That was enough for the American Cancer Society, which brought together a wide range of cancer experts to offer nutrition guidelines for cancer survivors, concluding that, if anything, soy foods should be beneficial. Since then, two additional studies have been published for a total of five—five out of five studies that tracked more than 10,000 breast cancer patients—and they all point in the same direction.

Pooling all of the results, soy food intake after breast cancer diagnosis was associated with both reduced mortality and reduced recurrence—that is, a longer lifespan and less likelihood that the cancer comes back. This improved survival was for women with estrogen receptor negative tumors and estrogen receptor positive tumors, and for both younger women and for older women.

Pass the edamame.


Flaxseeds are protective for likely the same reasons. For more on this, see my videos Flaxseeds and Breast Cancer Survival: Epidemiological Evidence and Flaxseeds and Breast Cancer Survival: Clinical Evidence.

What about women who carry breast cancer genes? I touched on that in BRCA Breast Cancer Genes and Soy and Should Women at High Risk for Breast Cancer Avoid Soy?.

What about genetically modified soy? See GMO Soy and Breast Cancer.

Who Shouldn’t Eat Soy? An excellent question I answer in that video.

For even more information on soy, see:

Not all phytoestrogens may be protective, though. See The Most Potent Phytoestrogen Is in Beer and What Are the Effects of the Hops Phytoestrogen in Beer?.

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:

Consider the Evidence When You Make Life-or-Death Decisions

In the 1940s and ’50s, the American Medical Association was not only saying that “smoking in moderation” wasn’t a problem, but that, on balance, it may even be beneficial. After all, most physicians themselves smoked, so how bad could it be? With such a position taken by one of the country’s leading medical groups, where could you turn if you just wanted the facts?

According to one tobacco company ad, “science advances new data that may completely change your idea of cigarettes!” And what might those new data tell us? “She was too tired for fun…and then she smoked a Camel.” (You can see the unbelievable ads in my video Evidence-Based Eating, starting at 0:29). In another ad, baseball legend Babe Ruth told us, “Now! Medical science offers proof positive!” that the brand he was hawking is the safest to smoke of all the leading cigarettes—well, he told us, that is, when he still could talk, before he died of throat cancer.

Now, some of the science-based evidence did leak out, causing a dip from an average of 11 or so cigarettes a day per person down to 10, as you can see at 0:50 in my video, but those who got scared of possible health risks from smoking could always choose “[t]he cigarette that takes the FEAR out of smoking!” Even better, why not choose the cigarette that “gives you the greatest health protection?”

Had a SmokingFacts.org website existed during the time of these outrageous ads making such outrageous claims—a site that delivered the science directly to the people, bypassing commercially corruptible institutional filters—it would have featured a study of Seventh-day Adventists in California in 1958 that showed that nonsmokers may have at least 90 percent less lung cancer than smokers. With so much money and personal habit at stake, there will always be “dissenters.” Given the seriousness of these diseases and the sum total of evidence, though, we shouldn’t wait to put preventive measures in place.

If you’re a smoker in the 1950s in the know and privy to the science-based realities of smoking, you realize the best available balance of evidence suggests your smoking habit is probably not good for you. So, what do you do? Do you change your smoking habits, or do you wait? If you wait until your physician tells you—between puffs—to quit, you could have cancer by then. If you wait until the powers that be officially recognize it, like the Surgeon General did in the subsequent decade, you could be dead by then.

It took more than 7,000 studies and the deaths of countless smokers before the first Surgeon General report against smoking was finally released in the 1960s. Wouldn’t you think that after the first 6,000 studies or so, they could have given people a heads up? One wonders how many people are suffering needlessly right now from dietary diseases.

Let’s fast-forward 55 years to a new Adventist study out of California warning Americans about the risks of something else they may be putting in their mouths: “Vegetarian diets are associated with lower all-cause mortality.” It’s not just one study either. According to a recent review, a total sum of evidence suggests that mortality from all causes put together, including many of our dreaded diseases were significantly lower in those eating more plant-based diets. As well, “[c]ompared with omnivores, the incidence of cancer and type 2 diabetes was also significantly lower in vegetarians.”

So, instead of someone going along with America’s smoking habits in the 1950s, imagine you or someone you know is going along with America’s eating habits today. With access to the science, you realize the best available balance of evidence suggests your eating habits are probably not good for you. So, what do you do? Do you change your eating habits, or do you wait? If you wait until your doctor tells you—between bites—to change your diet, it could be too late.

Just like most doctors smoked back then and didn’t tell their patients to change, despite the overwhelming evidence published for decades, most doctors today continue to eat foods that are contributing to our epidemics of dietary disease.


For more on this topic, check out my series of videos on parallels to smoking and the tobacco industry’s tactics, including:

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:

How Could There Be Such a Disconnect Between the Science and Medical Practice?

“Most deaths in the United States are preventable and related to nutrition.” According to the most rigorous analysis of risk factors ever published, the Global Burden of Disease study, funded by the Bill and Melinda Gates Foundation, our diet is both the number-one cause of death and the number-one cause of disability in the United States, having bumped smoking tobacco down to number two. Smoking now kills about a half million Americans every year, whereas our diet kills thousands more.

If most death and disability is preventable and related to nutrition, then, certainly, nutrition is the number-one subject taught in medical school and the number-one topic your doctor talks with you about, right? How can there be such a disconnect between the science and the practice of medicine?

Let’s do a thought experiment. Imagine you’re a smoker in the 1950s. The average per-capita cigarette consumption was about 4,000 cigarettes a year. Think about that. In the 1950s, the average American smoked half a pack a day.

My video How Smoking in 1959 Is Like Eating in 2019 shows a series of 1950s tobacco ads featuring media stars, famous athletes, and even Santa Claus telling you to smoke. The message was clear: If you wanted to keep fit and stay slender, you made sure to smoke. Magazine ads also encouraged you to eat hot dogs to keep yourself trim, as well as lots of sugar to stay both slim and trim. One ad even claimed that sugar was less fattening than apples. Apples! Though one internal tobacco industry memo stated, “Apples connote goodness and freshness and we see many possibilities for our youth-oriented cigarette with this flavor.” They wanted to make apple-flavored cigarettes for kids. Shameless!

As those 1950s ads tell us, in addition to staying “fit,” staying “slender,” and “guard[ing] against throat-scratch”, “for digestion’s sake,” you could smoke. “No curative power is claimed for Philip Morris,” read one ad, “but—an ounce of prevention is worth a pound of cure.” Heeding that advice, it’s better to be safe than sorry, so you’d better smoke.

Like eating, smoking was a family affair. Marlboro ads featured babies with comment bubbles saying, “Gee, Mommy, you sure enjoy your Marlboro,” “You’re darn tootin my dad smokes Marlboro…he knows a good thing,” and “Just one question, Mom…can you afford not to smoke Marlboro?” In another ad from the 1950s featuring a stereotypically  nuclear family, the dad is given cartons of cigarettes from his doting children—one boy and one girl, of course—and even the dog has a carton as his doting wife looks on.

“Blow in her face and she’ll follow you anywhere” was one tobacco company’s tagline, and “No woman ever says no to Winchester” was another. After all, cigarettes are “so round, so firm, so fully packed.” After all, John Wayne smoked them…until he got lung cancer and died.

Back then, even the Flintstones were smoking, and so were the doctors. This is not to say there wasn’t controversy within the medical profession. Yes, some ads showed doctors smoking Camels, but, in others, physicians preferred Lucky Strikes, so there was some disagreement. Indeed, “eminent doctors…on high and impartial medical authority…call for Philip Morris.” Even “leading nose and throat specialists” couldn’t agree which cigarette is better for your throat. Probably best to stick to the science, and, touts another ad, “more scientists…smoke Kent…” This should not be rocket science—but even the rocket scientists had their favorite Viceroys for the “man who thinks for himself.”

Can you guess why the American Medical Association (AMA) “went on record as withholding endorsement of the Surgeon General’s Report on Smoking and Health, which documented the important role of cigarettes in…lung cancer”? A “gift from the tobacco companies” of ten million dollars may have had a little something to do with that. But why weren’t more individual doctors speaking out? There were a few gallant souls ahead of their time writing in to medical journals, as there are today, standing up against industries killing millions, but why not more? Maybe it’s because “the majority of physicians themselves smoke[d] cigarettes,” just like the majority of physicians today continue to eat foods that contribute to our epidemics of dietary diseases. What was the AMA’s rallying cry back then? Everything “in moderation.” The AMA said “[e]xtensive scientific studies have proved that smoking in moderation” is okay.

Eating the Standard American Diet today is like being a smoker in the 1950s. Just as smoking was rampant back then, think about what we’re feeding even hospital patients to this day.

We don’t have to wait until society catches up with the science. Sometimes it takes a whole generation for things to change in medicine. The old guard of smoking physicians and medical school professors die off, and a new generation takes its place—but how many people need to die in the interim?


I try to answer the question that arises in the minds of pretty much anyone dipping even  a single toe into the lifestyle medicine literature: “Wait a second. If this were true, why didn’t my doctor tell me?” If, for example, our number-one killer can be reversed through diet, why isn’t it front-page news and taught to every medical student, broadcast from every mountaintop by medical organizations, and featured in our government dietary guidelines? Still confused? Check out my other videos that address these questions:

For more on the parallels between smoking then and eating today, see:

Is the risk of smoking really comparable to following the Standard American Diet, though? See Animal Protein Compared to Cigarette Smoking and Will Cannabis Turn Into Big Tobacco?.

In health,
Michael Greger, M.D.

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