Debunking the ‘Soy Boy’ Myth, With Science

In the last decade, a new pejorative has emerged for men perceived as insufficiently masculine: “soy boy.” The term implies that soy consumption “feminizes” men by altering their hormonal balance — a flatly incorrect claim rooted in a complete misunderstanding of biology. It’s worth taking some time to debunk the “soy boy” myth, as the term is both scientifically inaccurate and reinforces toxic norms about gender, race and masculinity.

The False Claims of ‘Soy Boy’ Fears

While there’s no official definition of the term, believers of the “soy boy” archetype generally allege that eating soy does one or more of the following things:

• Raises men’s estrogen levels
• Lowers men’s testosterone levels
• Causes men to experience sexual dysfunction or decreased libido
• Increases a man’s risk of getting breast cancer
• Causes men to grow breasts

As a result of these alleged side effects, men who eat soy effectively become emasculated, or “feminized” — so the story goes, at least. But is this really the case?

No, it isn’t. Study after study has debunked these claims. Eating soy has no effect on men’s hormone levels or sex drives, doesn’t cause men to grow breasts or experience erectile dysfunction and doesn’t decrease men’s libido. And far from promoting breast cancer, eating soy might actually decrease one’s chances of getting certain cancers.

The Harm of the ‘Soy Boy’ Stereotype

At a glance, “soy boy” might just seem like a silly slang term for an effeminate man. But the term is actually much more insidious than it might appear, and has several misogynistic and racist connotations.

For one, “soy boy” is never used as a compliment. It’s always meant as an insult, and specifically, as an insult toward men perceived as being insufficiently masculine, or likewise, too feminine. The term is premised on the idea that it’s bad for men to be effeminate, or that men are somehow worth less if they exhibit qualities that society perceives as “feminine.” This is a misogynistic belief, as it’s rooted in the devaluing and othering of “female” characteristics.

Racist Undertones of the ‘Soy Boy’ Insult

“Soy boy” can also have racist undertones, for two reasons. In the West, Asian men have long been stereotyped as effeminate, unmasculine and asexual. Given that soy consumption is much higher in Asian countries, the idea that soy drinkers are puny “soy boys” only furthers this racist stereotype of Asian men.

The second reason has to do with lactose, which is present in dairy milk but not soy milk. The majority of people on the planet have trouble digesting dairy, and people of color are especially susceptible to lactose intolerance. By contrast, only about 15 percent of Caucasians are lactose-intolerant.

In other words, the majority of white people can drink dairy milk without any health complications, but the majority of people of color can’t. This makes soy milk an especially attractive proposition to people of color — which, in turn, means that men of color are disproportionately likely to be labeled “soy boys.”

There’s undoubtedly a social and political element to the “soy boy” insult. Meat-eating has long been associated with masculinity, which has led to veganism being associated with a lack of masculinity. Soy milk is popular among vegans, so it’s not surprising that some people would find a way to accuse soy-drinking men of being effeminate.

Breaking Down the Science of Soy

The term “soy boy” isn’t just a throwaway insult; it’s also a a set of claims about soy’s effects on the male body. In order to debunk these claims, it’s necessary to dive into the science behind soy and its effect on the human body.

The Difference Between Phytoestrogen and Estrogen

Much of the confusion around soy’s health impacts stems from the fact that it contains isoflavones, a type of phytoestrogen. Despite its name, phytoestrogen is not a type of estrogen.

Rather, phytoestrogen is a different compound that’s found in over 300 plants, including soybeans. It’s named as such because it’s structurally similar to estrogen, and can bind to the same types of neuroreceptors as estrogen.

“People may be thinking, okay, phytoestrogen, estrogen. These things are basically the same thing, right?,” Noah Praamsma, the Nutrition Education Coordinator with the Physicians Committee for Responsible Medicine, tells Sentient. “If I eat phytoestrogens, doesn’t it sort of logically follow that I’ll be taking on these female characteristics?”

It doesn’t, Praamsma says. Mountains of research has shown that consuming phytoestrogen has no effect on a person’s estrogen levels, and eating isoflavones, even in extremely high quantities, does not cause men to experience “feminization,” or take on biologically female attributes.

“It’s just really important to emphasize that phytoestrogens and isoflavones that you eat in your diet don’t actually affect the amount of estrogen that your body produces, or the amount that is circulating,” Praamsma says.

The Effect of Isoflavones

This all isn’t to say that phytoestrogen and isoflavones have no effect on the human body at all. In sufficient doses, they’ve been shown to improve cognitive function, promote skin health, reduce cholesterol and help stave off breast cancer.

But in order to enjoy these benefits, one has to eat a lot of isoflavones — at least 50mg every day, according to one study, and potentially as high as 160mg a day, depending on the health benefit in question.

For perspective, the average Westerner consumes around 2mg of isoflavones every day; in Asia, where soy products are more of a dietary staple than in the West, the average person consumes between 15 and 50mg of isoflavones every day.

To be sure, too much of any food is a bad thing. But even the most devoted soy lovers will probably get nowhere near that tipping point. For instance, suppose a man eats an entire 100g block of tofu, and drinks 20 ounces of soy milk, every day. That’s undoubtedly a soy-heavy diet — but still comes out to only 85mg of isoflavones per day, which is well within the healthy range.

Soy Doesn’t Give Men Breasts or Erectile Dysfunction

While study after study shows that soy doesn’t have a feminizing effect on men, proponents of the “soy boy” trope sometimes allege that eating soy can make men develop breasts, or experience erectile dysfunction. This isn’t true, but it’s helpful to look at the origins of these claims to understand why they’re not true, and what the science actually says.

In 2008, a report of a 60-year-old man who mysteriously developed gynecomastia, or enlargement of the breast tissue, received significant media attention. The man also began experiencing erectile dysfunction and a decrease in his libido around the same time as his gynecomastia symptoms, and scientists eventually traced these changes to his consumption of soy milk. When he stopped drinking soy milk, his symptoms subsided.

This single case led to a flurry of media coverage. Men’s Health ran with it, suggesting — in a lengthy article that appears to have since been deleted from its website — that soy might be “the most dangerous food for men.” Even today, mainstream publications are still debunking the “soy makes men grow boobs” myth.

The reason it’s a myth is that the man in this study was consuming an astronomical, abnormal amount of soy — around three liters of soy milk every day, he told the researchers. That comes out to over 300mg of isoflavones every 24 hours —six times higher than the highest estimate of average daily soy consumption in Asia, where soy consumption is already higher than anywhere else in the world, and over 100 times higher than the average Westerner’s daily soy consumption.

Needless to say, this man was an outlier — the study referred to him as a “very unusual case” — because most humans, male and female, don’t eat anywhere near that much soy. Drinking this much soy milk almost certainly threw this man’s entire diet out of whack, given the caloric and fat content of soy milk; in addition, there’s some indication in the study that he may have been more sensitive to isoflavones than the population at large.

Two years later, a meta-analysis of existing research found no evidence that isoflavone consumption, even when significantly higher than the average intake in Asian countries, causes men to grow breasts. In one study, 300 men ate 100mg of isoflavones every day for three years, and showed no signs of gynecomastia.

In 2018, 10 years after warning readers that soy might make them grow breasts, Men’s Health published an article touting the health benefits of soy milk.

Praamsma also traces the “soy boy” myth to a 2003 study finding that male rats experienced changes in their reproductive organs and general sexual dysfunction when fed significant amounts of genistein, a type of isoflavone, in their infancy. This finding may also have contributed to the “soy boy” trope — but it shouldn’t, Praamsma stresses, because the results of studies involving non-humans often can’t be extrapolated to humans.

“There’s a sort of flawed logic in assuming that everything that happens in a rodent is therefore a predictor of what happens in humans,” Praamsma explains. “That’s just not the case.”

Indeed, later research found several biological reasons why rodents’ reactions to isoflavones don’t necessarily apply to humans. Even the press release announcing the 2003 study acknowledges this, saying at the outset that “these findings do not indicate that genistein has a similar effect in humans.”

Soy Doesn’t Cause Breast Cancer — But It Might Help Prevent It

It’s been claimed that drinking soy milk increases a man’s chance of getting breast cancer. This is also false, and is based on a misunderstanding of how estrogen and phytoestrogen work.

There are two different mechanisms by which the brain receives and processes estrogen: alpha receptors and beta receptors. Alpha receptors increase the speed at which cells divide, and they’re the primary receptors to which estrogen bonds. As a result, elevated estrogen levels can lead to runaway cell growth and, potentially, cancer.

But beta receptors have the opposite effect: they inhibit cell growth. And it just so happens that phytoestrogen bonds primarily to beta receptors, not alpha receptors. The result is that the isoflavones in soy, far from promoting breast cancer, can actually reduce one’s risk of getting breast cancer.

The Bottom Line

It’s beyond time that we ditch the “soy boy” stereotype, and the counterproductive beliefs about masculinity, race and nutrition that fuel it. The science is clear: soy doesn’t alter men’s hormones, or otherwise emasculate them. In reality, soy milk is a healthy, affordable and sustainable alternative to dairy milk for men and women alike.