Have You Heard the One About Soy and “Man Boobs?” Well, It’s a Myth.

There's this persistent story going around that refuses to be put to rest, that eating faux meat made from soy, drinking soy milk or too much tofu will lead to man boobs. The latest version has it that too many Impossible Burgers will cause men to grow breasts. But this is just the newest iteration of the age-old worry that soy contains isoflavones, which are similar to estrogens and that eating too much of the stuff will promote the growth of breasts in men.

Part of the problem is that the meat and dairy industry allies are stoking the flames of this scenario. Another issue is that as men age, grow fatter, or take certain medicines, there are rising statistics of the medical condition known as gynecomastia, but all reliable reporting tells us that soy is not the culprit. Here is the latest information that The Beet could find on the truth about the connection between eating soy foods and gynecomastia. If you want to skip to the bottom line: Hit the gym.

Soy contains isoflavones, which are plant-based molecules that mimic estrogen, but the latest research shows that plant-based phytoestrogens may actually protect against the body's own production of real estrogens, according to studies into the connection in women (most of the research is around breast cancer). Estrogen is also present in small amounts in the male body, and if testosterone drops for any reason, such as taking certain medications, then this balance can be disrupted. As a result, men may feel breast tissue tenderness, swelling or growth. But in most cases, "man boobs" are simply the result of excess body fat.

Eating or drinking soy—or foods high in soy, such as tofu—have been studied for decades by medical researchers seeking to answer the question: Do the isoflavonoids in soybeans act as estrogens in the human body? The conclusion is a resounding: No.

The Washington Post put to rest the fears about "man boobs", in a story called: "Dear men: There’s no evidence that eating Impossible Whoppers will give you breasts." The Post interviewed experts on the topic and the conclusion was that soy appears safe for men.

Many conditions can cause men to develop breasts, including fluctuations in male hormone production since testosterone and estrogen are both involved in the regulation of sex drive and other vital functions. These hormonal fluctuations can cause man boobs, which affect 1 in 4 men between the ages of 50 and 69. (Medication can also be involved, especially anti-androgens used to treat an enlarged prostate, prostate cancer, and other conditions.)

One study of children raised on soy formula, who could not tolerate cow's milk, found that kids are raised on soy milk showed no gynecomastia when they got older. They also did not experience early puberty or other changes that would indicate the plant estrogens were acting like the real thing in their bodies. In all the review studies, "no feminizing effects" were found.

There was an outlier of a case, back in 2008, of a sixty-year-old man who was drinking three quarts of soy milk a day and presented with gynecomastia. When he went off the soy milk, his breasts deflated. But before you think, "Ah-Ha!" that's the equivalent in terms of dosage as 361 mg a day, in comparison to typical intake among men in Japan of 46 mg a day. So clearly overdosing on isoflavone-containing soymilk can lead to untoward effects. But when he halted this routine, his body returned to normal.

The bulk of the science on soy and breast tissue is around breast health in women, but a look at populations in parts of the world where people eat a lot of soy indicates that men are unaffected. In Asia, where men and women eat more soy foods than the rest of the world, there is no increased incidence of gynecomastia. (Nor is there elevated breast cancer risk.) So, the conclusions are that soy does not lead to the growth of male breast tissue.

"Asians have been eating soy products for millennia and don’t seem to be any the worse for it. They have among the longest lifespans and best health, at least in [those who follow] classic diets,” New York University nutrition professor Marion Nestle told The Post. “There is a special concern about . . . men and boys who eat soy products, but again, if you look at populations that eat a lot of soy products, there is no evidence of particular problems. No, they don’t grow breasts.”

Vox did a piece back before the new alternative meats came on the scene—and so could not be accused of "picking sides" in the scaremongering or warring factions. Vox reported that "Whenever researchers have studied the link, they haven't found any association. In a 2010 review of the medical evidence, researchers wrote that "isoflavones do not exert feminizing effects on men," at least not when consumed at levels typical of many soy-heavy Asian diets. Another 2004 study, comparing babies who were fed soy milk with a control group, found no "estrogen-like" hormonal effects in the soy drinkers.

The Post piece places some of the blame for the fear on James Stangle, a doctor of veterinary medicine in South Dakota, who pointed specifically to the Impossible Whopper as a source of concern, saying that men should not wolf down too many of them.

In a recent report for Tri-State Livestock News, Stangle said the Impossible Whopper, which bases its protein source on soy, contains 44 milligrams of estrogen, compared to 2.5 nanograms in the beef Whopper. He fails to mention the fact is that study after study has concluded a "moderate" amount of soy (a few servings a day)  is not only safe but likely to be protective against an abundance of estrogen production in the body. In The Beet's story on the truth about soy and breast cancer, our research concluded that the studies all point to soy as safe. The question we set out to answer:  Would too much of the isoflavones in soy act as an endocrine disruptor?

Tri-State Livestock News is, a trade publication for the livestock industry, and The Post’s Laura Reiley wrote last year that “many of the country’s 800,000 cattle ranchers have declared war on newcomers Impossible Foods and Beyond Meat." (Beyond Meat does not contain soy.) Other media outlets have picked up the story, and the meat and dairy industry continues to keep it alive.

Last year, The Beet sent Marisa Cohen, respected health and medical writer, to interview doctors about soy and health, specifically related to breast cancer risks. Our conclusion: Phytoestrogens are safe, and may even help ward off breast cancer because Isoflavones are much weaker than the estrogen produced in the body. So if those weaker substances replace the more potent hormone in your cells, they could ward off cancers that need stronger signals from estrogen to thrive. By this argument, they would also protect against estrogen-driven "man boobs".

The expert source we called on, Marisa C. Weiss, MD, the founder and chief medical officer of BreastCancer.org, explains the way soy works in lowering the risk of endocrine disruption. But she also points out that soy replaces meat and dairy, so the lower risk could be related to the fact that the person eating soy eats less meat and dairy, and dairy does contain actual estrogen that has been fed to cows to promote milk production. Plant estrogen is not actual estrogen, but the hormones in dairy are. 

So the questions Weiss asks in that context are this: “Is the soy lowering their risk of breast cancer, or is it because they are eating less meat and less dairy? Is it because they tend to be thinner? We don’t really know if it’s the soy itself, but we do know that people who eat soy throughout their life have a lower risk of breast cancer.”

There appears to be no connection between the intake of a modest amount of soy products like tofu with the development of man boobs. Modest intake is usually defined by experts as up to two servings of soy a day. The other, rather obvious way to reduce man boobs, is to lose weight or maintain healthy body fat, and to be fit, work on strength training to boost lean body mass composition. To be healthy, fit, and maintain a healthy weight and lean body composition, a diet of plant-based whole foods is recommended by doctors, who are concerned with their patients' overall heart health and wellbeing.

The latest research, published in the Journal of the American Heart Association, shows that plant-based diets are associated with a lower risk of not only heart disease but ALL causes of mortality in a general population of middle-aged adults.

People who eat fewer animal products and refined carbs were 32% less likely to die of heart disease and 25% less likely to die of all causes during the course of the study.

So, if you don't want man boobs, then exercise, eat healthily (including a diet of plant-based whole foods) and keep your weight under control. As for soy? Based on the expert sources and latest studies, The Beet believes that a modest amount of soy is healthy, which is up to two servings a day.