Soy Sorry: Why soy is NOT causing your man boobs

One big reason people (especially men) seem to stray from trying a vegan diet is a fear of soy. The thing that apparently scares men the most is the claim that there’s something in soy that makes men more feminine. And within that, is the fear of man boobs–also known as ‘moobs.’ Dudes do not want moobs.

That’s an especially troubling claim because soy is one of the best non-animal sources of protein. So if you’re taking meat off your plate, and you don’t want to lose those epic muscle gainz from the gym, soy can be a common food choice. Plus, when most restaurants and recipes have a high-protein vegetarian option, it’s usually soy-centric, like tofu.

Rest assured, soy is great. The bad stuff you’ve heard about soy is often completely nonsense or very much unfair. All of these anti-soy deceits are a distraction from things actually cause, or are associated with, man boobs and other feminizing characteristics.

If man boobs are a concern of yours, you should know what actually causes them. The vast, vast majority of cases of man boobs are a result of one thing: hormone changes that happen when males either hit puberty, or when males hit middle age. The simple explanations why: hormones can fluctuate as males go through puberty; and testosterone production decreases as men age. For many men, when this happens, the man boobs don’t go away. While it would be convenient to blame a single food or substance, it’s almost certainly not the case. And as I’ll elaborate on throughout this post, the bigger point is: man boobs have absolutely nothing to do with soy. Another common cause for man boobs is due to being overweight and, for various reasons, fat collects in the chest area. There are some other known (albeit far less common) causes that I’ll delve into later. But one thing’s clear: according to virtually all of the leading, classically trustworthy sources on what causes man boobs, soy is not a cause!

What sucks is that the anti-soy seed is already planted in many guys’ heads. Countless men of all ages either fear getting man boobs, or they already have them. And the word “soy” is often connected with it, and other hormonal conditions. You might hear friends or acquaintances conveniently blame an acne breakout (or some other random potentially hormone-related health issue) on tofu they ate earlier in the week. Is it fair to blame soy? Nope, but it still happens.

No food is perfect. But many of us have associations with certain foods that we can’t kick, even though the actual factual science tells us otherwise. Usually we can thank the psychology and manipulation of marketing and advertising. Meat and dairy come with major health issues, yet people connect those foods to ideas like manliness, muscles and strength. Parents teach that to their kids, and the powerful dairy industry makes sure to overwhelm us with that connotation.

Soy, as far as I know, doesn’t have any ‘Got Soy?’ campaigns stressing the many nutritional benefits, or fast food chain commercials with a muscular bearded bro chomping down on a tofurky sandwich. Instead, the soy marketing void has been filled by worries of “This is a weird food with weird ingredients. Maybe I should avoid it. Maybe it’s causing weird things to happen to me.”

In fact, much of the anti-soy stuff comes from blogs and sources that are flat out untrustworthy—mainly because they don’t appear to rely on trustworthy science and reliable sources. I  stand by the sources I’ve relied on—certainly more than the anti-soy paleo bloggers who cite random stories by acupuncturists listed on quack watch websites. Or shows like The League, which had an episode in 2010 where a character ate a lot of soy and developed man boobs. After reading as much as I have about soy, I can confidently say that the health claims in that episode were not vetted by a reliable medical professional.

That’s the unfair challenge vegetarians and vegans are up against. The truth is, a lot of non-vegan foods, like cow’s milk, should probably have the reputation soy has.

That’s what led me on a quest to read everything I possibly could on the topic. Now I’ve spent more time studying soy (and moobs) than I care to admit. This blog post is a summary of what I’ve discovered.

And before I go any further…this a really complicated area. Scientists and medical professionals continue to build on their understanding of soy and hormones (and man boobs for that matter). But there’s enough to the story out there—from legitimate sources—to illuminate soy’s impact on men, and whether it’s a reasonable concern if you want to avoid moobs or any other feminizing traits. (Spoiler: it’s not a concern. Soy is a great food option, and much of the negative stuff that’s written about it is straight up lies, or it’s a completely exaggerated and embellished criticism made without any context.)

All I ask is that, even if you’re skeptical of me—the avocadbro—please, at the very least, don’t listen to the paleo bros, or their naturopath health gurus, on this subject. If you’re truly concerned about moobs, the first place to go is a board-certified medical doctor.

What is soy, and what is in it that worries people?

Soy is a bean. Loaded with protein and fiber. It can be turned into milk or cheese. It can be cubed as tofu or tempeh and absorb delicious flavors in cooking. It can be steamed or boiled and eaten as edamame. It’s common in a lot of Asian cuisines, especially Chinese, Japanese, Taiwanese, Vietnamese and Thai. Soy protein is a main ingredient in a lot of vegan versions of burgers, chicken and hotdogs. It’s a high-quality protein supplement in protein bars and shakes.

Soy also has something in it called isoflavones. “What the #@&% are isoflavones?!,” you might ask. They’re part of a class of compounds called phytoestrogens. Right here is where you might say “Phyto…estrogen? Estrogen?! Oh no. Estrogen is a female hormone, right? And females have boobs. Boobs. Man boobs. Soy gives you man boobs.”

Not so fast.

Phytoestrogen isn’t animal estrogen, like the kind found in humans, cows and chickens. It’s plant estrogen. Plant estrogen is, indeed, chemically similar to animal estrogen—but how it acts in the human body is what really matters. It turns out, it acts very differently.

Last I checked, soybean plants don’t have boobs. In fact, soybean pods look like ripped, hairy arm muscles. And they’re green like The Hulk. What’s more manly than green, bulky, hairy arms?

Source: N. Brenner, Mizzou

I mean, look at those things. They’re ripped. Case closed.

For real though—men, believe it or not, have estrogen in their bodies by default. Even if a man has never touched soy (or a woman) in his life, his body still naturally has estrogen in it.

The estrogens that humans make is the same estrogen that’s found in animals: whether human, cow, chicken, lamb, pig, and so on. Animal estrogens are the primary ‘female’ sex hormones. Animal estrogens play a major role in growing breasts. Again, animal estrogens are found inside animals, whether human, or cow, or pig, or chicken. It’s essentially the same compound, no matter the animal.

The animal estrogen that’s naturally in humans is called endogenous estrogen (which means it’s produced inside the body). Then there’s exogenous estrogens (which are estrogens that make their way into our bodies from external sources). Animal hormones from consuming meat, eggs and dairy are examples of exogenous estrogens.

Men, of course, have a lot more testosterone (the ‘male’ hormone) than they do estrogen. The balance of these two hormones, as you’ll see, plays a major role in the development of man boobs.

So we’ve got plant estrogen. And we’ve got animal estrogen–both the kind that’s produced in the body and the kind we get by eating other animals and their milk. To make matters somewhat more complicated, humans actually encounter another category of estrogens.


This next type of estrogen is called industrial xenoestrogens. These estrogens might actually be in the news even more than soy, because so many products we consume and encounter every day contain these industrial estrogens.

Xenoestrogens include a whole bunch of things like chemicals found in plastics (BPA and BPS are the most infamous), certain pharmaceuticals, pesticides, pollutants, additives in food and cosmetics, hormone drugs, and too many more to list. Confusingly, “xenoestrogens” are sometimes defined to include plant estrogen, which makes things all the more difficult to keep track of.

Real quick, let’s sum up the different estrogens:

  1. Animal estrogen that humans make inside the body (endogenous).
  2. Animal estrogen that humans eat or encounter (exogenous).
  3. Plant phytoestrogens that humans eat or encounter (exogenous).
  4. Industrial xenoestrogens that humans eat or encounter (exogenous).

What’s the difference between them all? 

Plant estrogen is considered to be far weaker than animal estrogen and industrial xenoestrogens.

Whoa, that’s a huge font. But this is an important point.

The first important difference is how do these different estrogens compare in terms of potency and power. Plenty of sources summarize the scientific understanding. Tulane University’s eHormone website sums it up as follows:  “[P]hytoestrogens are weaker than the natural [aka animal] estrogen hormones . . . found in humans and animals or the very potent synthetic estrogens used in birth control pills and other drugs.”

And, according to a paper from European Society of Human Reproduction and Embryology,  “The natural [aka animal] estrogen estradiol is at least 10 000-fold more potent than most identified environmental xenoestrogens . . .”

One thing seems to be apparent–that animal estrogens are in their own playing field in terms of potency. After all, animal estrogen is what humans and animals (whether it’s a cow, pig, chicken, duck, deer or lamb) all have naturally coursing through their bodies.

Plant estrogens aren’t just weaker than animal estrogens. They’ve also been found to actually block animal estrogen’s effects in breast tissue. This was reported in a study out of Wake Forest University. The reasoning, again according to Tulane University’s eHormone: “Phytoestrogens . . . may lower a person’s lifetime exposure to natural estrogens by competing for estrogen receptor sites or changing the way natural estrogens are broken down.” So, by taking the place of stronger animal estrogens in the body, the weaker estrogens in soy apparently can lower your overall estrogen exposure.

Digging a little deeper into that fact–it turns out there are 2 main types of estrogen receptors in people. Phytoestrogens, including those from soy, primarily bind to the “beta” receptor, according to the Journal of Pharmaceutical Sciences. In the breast area, activating the beta receptor has an anti-estrogenic effect, according to the journal Nutrition Today.

Then, from a report published the Planta Medica medical journal: “[P]hytoestrogens have also been noted to be inhibitors enzymes involved in the synthesis of estrogen. This in turn leads to decreased circulating levels of free estrogen and less peripheral conversion of androgens to estrogens . . . Some phytoestrogens are known to decrease the conversion of androgens to estrogen by blocking the aromatase enzyme system.”

Well, damn. One thing’s for sure, this is a complicated area. But at the very least, hopefully at this point you’re starting to realize that maybe soy isn’t half bad when it comes to estrogen and man boobs.

Where industrial estrogens fall into this animal estrogen vs. plant estrogen conversation isn’t totally clear. Mainly because there are many, many types of industrial estrogens (and plant estrogens, for that matter), and how these estrogens interact with the body differs depending on context and other variables–but as a general matter, plant estrogens are frequently said to be the weakest; animal estrogens are frequently said to be the strongest. Industrial estrogens–because there are so many types–appear to be all over the map in terms of potency.

In fact, BPA (the estrogenic chemical found in many plastics) is often said to be very, very weak. One report described it as “so weak that even at levels of exposure 4000-fold higher than the maximum exposure of humans in the general population there are no discernible adverse effects.” Yet, despite that report, there’s still debate among experts about exactly how worrisome BPA is in terms of its estrogenic effects.

A researcher from North Carolina State who studies both soy and BPA said in 2009 that BPA and soy are comparable in terms of estrogenic effects. (This researcher seems to be quite wary of soy, but my feeling is–if BPA is so extremely weak, then shouldn’t that be reassuring since soy is also so weak?) In any event, in 2016, a study from that same researcher found that soy actually mitigates some negative effects of BPA.

Soy seems to win this first key distinction about how strong (or potent) these compounds are–but there’s an even more important follow-up question: if soy is so weak, and animal estrogens are so strong, it probably doesn’t matter unless our bodies actually absorb them and are affected by them. What effects do plant and animal estrogens actually have on people?

Plant estrogen is absorbed into the body longer than animal estrogen, and apparently more easily. Phytoestrogens last in the bloodstream for about a day. Yet, according to a 2012 CDC nutrition report: while “phytoestrogens are much less potent than endogenously [aka internally] produced estrogens” they “can be present in much greater quantities (100 to 1000 times the concentration of endogenous estrogens).” Of course “endogenous” estrogen means animal estrogen produced inside the body. What about exogenous animal estrogens, like the kind found in cow’s milk, eggs and meat?

I found this report sponsored by the dairy industry that found that consuming estrogen (from cow’s milk ) doesn’t affect “blood levels” of estrogen, because the liver filters a bunch of it out. Yet, seemingly in contradiction to that study, is another study from the journal Pediatrics International, which concluded: “The present data on men and children indicate that estrogens in milk were absorbed, and gonadotropin secretion was suppressed, followed by a decrease in testosterone secretion. Sexual maturation of prepubertal children could be affected by the ordinary intake of cow milk.” To be fair to dairy, as Jack Norris, RD, points out, the subjects in the second study drank a lot of milk in a short amount of time. Then again, the first dairy study was on mice, the second dairy study was on people. Like you and me!

So, it’s well documented that soy gets absorbed into the bloodstream, apparently moreso than dairy. But so what? To me, that doesn’t get to the heart of the matter: regardless of how much and how long of each of these compounds humans are exposed to, which of these estrogen types actually make an impact on people? That right there, is what matters most. Phytoestrogens may last longer than the body, and be present in higher quantities. But aren’t they far weaker? Don’t they block actual, stronger, animal estrogens? Does how long it’s present in the body actually matter? Even if animal estrogens from animal foods (meat, eggs, dairy) aren’t highly absorbed in the bloodstream, aren’t they far more potent? Does its presence in the body (whether absorbed in great amounts, or not) still make an impact?  In other words, if a tiny amount of actual, potent animal estrogen seeps into our bodies from cheese or yogurt or milk, how does its impact differ from the impact of the apparently weaker plant estrogen from soy?

This question that gets to the meat of the issue. Animal estrogen is said to be more powerful. Plant estrogen is said to be better absorbed in the body. Let’s see what actually makes a difference. And to show this difference, let’s compare soy with the biggest source of animal estrogens: cheese. Ladies and gentleman of all different bra sizes, on to the biggest battle of our time . . .


The biggest dietary source of animal estrogen is dairy. From the journal Food Chemistry: “Milk products supply about 60-80% of ingested female sex steroids. Eggs are a considerable source of any of the investigated steroids and contribute to the nutritional hormone intake in the same order as meat and fish (10-20%).”

For what it’s worth, “no estrogens” were found in plants, according to the journal. Although to be fair, the authors mean animal estrogen, not plant estrogen.

The following are all studies and reports that, generally speaking, are about dairy and soy’s effects on estrogen, testosterone, man boobs, sperm health, and/or other feminizing issues. Let’s see what the science (that I found) shows. I will update this as I come across other trustworthy reports.


The gist that I gathered is: dairy products contain estrogen, and plenty of scientists and doctors have found that some of it gets absorbed and messes with our hormones.

What about “hormone free” milk? One thing that absolutely needs to be mentioned, is that these studies and reports look at estrogen that occurs naturally in milk–as you’ll see many of the studies below point out. As you’ve undoubtedly come across, a lot of dairy, meat and egg products seem to advertise that they are “hormone free.” In reality, the labels usually say something like “free of synthetic hormones” or “free of added hormones” or they make specific mention to the fact a specific type of hormones, like “No added rBGH.” What these milk producers really mean is that there are no added hormones. There’s still plenty of naturally occurring animal hormones in meat and dairy. Think about it. Dairy comes from lactating female cows. These are creatures that are straight up teeming with estrogen, especially their lactations. This isn’t estrogen that the farmer added to the cow’s feed. Rather, this is estrogen that occurs naturally in these animals, especially ultra-hormonal, lactating female ones.

So what sort of impact do these hormones have?

From the International Journal of Cancer:

  • “Commercial cow milk contains considerable amounts of estrogens . . . The high estrogen content in the milk may be responsible for the promotional effects [of mammary tumors] acting in concert with other hormones . . .”

From Human Reproduction:

  • “We . . . found that dairy food intake was inversely related to sperm morphology and progressive motility. This association was strong for full-fat dairy foods, particularly cheese. . .”
  • “[O]ur findings on the relation between dairy intake and reproductive hormones suggest that dairy intake may be implicated in direct testicular damage.”

From journal Medical Hypotheses:

  • [I]ncreased consumption of animal-derived food may have adverse effects on the development of hormone-dependent cancers. Among dietary risk factors, we are most concerned with milk and dairy products, because the milk we drink today is produced from pregnant cows, in which estrogen and progesterone levels are markedly elevated.”

From the journal Fertility and Sterility:

  • Cheese intake was associated with lower sperm concentration.”

From the University of Osnabrück :

  • Milk consumption has already been identified as an aggravating factor in the acne ‘epidemic’ among adolescents, and preliminary successes have been reported with reduced milk consumption . . .”
  • “. . . drinking milk and consuming dairy products from pregnant cows exposes us to the hormones produced by the cows’ pregnancy, hormones that we were not designed to consume during our teenage and adult years . . . So what happens if exogenous hormones are added to the normal endogenous load? And what exactly is the source of these hormones?”
  • “Consider that, in nature, milk is consumed from a mother, whether human or bovine, until weaning occurs. Normally, the mother then ceases lactation before the next pregnancy occurs— so that consuming milk from a mother pregnant with her next offspring is not a common occurrence . . . Further, in nature the offspring consumes only the milk of its own species—but both of these natural rules are broken by humans.”
  • See here for more from the same author, this time as part of Nestle Nutrition Institute.

From the University of Medical Sciences in Iran:

  • “The naturally occurring hormones in dairy foods have biological effects in humans and animals, which are ranging from growth promoting effects that related to sex steroids . . .
  • “[I]t seems that steroid hormones are very potent compounds in dairy foods, which exerting profound biological effects in animals and humans . . . recently it is found that these compounds even at very low doses may have significant biological effects . . .

From the Journal of the American Academy of Dermatology:

  • “We found a positive association between intake of milk and acne . . . We hypothesize that the association with milk may be because of the presence of hormones and bioactive molecules in milk.

From the European Society of Human Reproduction and Embryology:

  • “The natural estrogen estradiol . . . the dietary exposure (from e.g. meat, dairy products and eggs) to the natural sex steroids is therefore highly relevant in the discussion of the impact of estrogens on human development and health.”

From the Journal of Chromatography:

  • The relatively high levels of catechol estrogens detected in milk products support the theory that milk consumption is a source of [estrogen metabolites] and their ingestion may have a dietary influence on cancer risk.”

From the American Academy of Dermatology:

  • [I]t should surprise no one that milk contains such a heavy complement of growth-enhancing hormones. Milk is, after all, specifically designed to make things grow . . .
  • “Our deeply-rooted beliefs about the wholesomeness of milk and dairy products should be reconsidered under careful, scientific evaluation. We are just beginning to re-assess the biological effects of milk and dairy products as foodstuffs. Human beings are the only species on earth that from the beginning of the perinatal period into adulthood are subjected to external hormonal manipulation . . . and differentiation processes in various cell and organ systems. Milk developed over the course of mammalian evolution as a highly complex, biologically active carrier of signals which was intended only to be consumed during infancy.”
  • The consumption of cow’s milk interferes with the sensitive endocrine regulatory network from the fetal period into old age.

From Human Reproduction Update:

  • “[T]he major sources of animal-derived estrogens in the human diet are milk and dairy products . . . By drinking 300 ml of milk per day, a child’s intake of estradiol-17 alone, the most potent estrogenic hormone, is approximately 10 ng per day. This is 4000 times the intake of environmental hormones or xenoestrogens, in terms of hormone activity.”

To be fair to milk, outside of some anecdotal reports, there aren’t any studies connecting it with the specific condition of man boobs. That strikes me as odd, because all of the above authorities show that milk is full of powerful animal estrogens, and those estrogens (even if not fully absorbed) can have a significant impact on our bodies and health. If nothing else, I hope the above shows that milk–whether in the form of organic kefir, or hormone-free cheese, or Greek yogurt, or cream, or butter, or whatever other food humans have been able to turn cow lactation into–is the biggest source of female hormones. Remember that next time you’re enjoying an ice cream cone on a hot summer day, worrying about whether your t-shirt is loose enough to hide your moobs.

Cows have been warning us all along.


All of those reports make dairy sound like the ultra-hormonal, acne-covered teenager of the food world. At this point maybe you’re taking Greek yogurt out of your shopping cart. But are you going to grab the soy yogurt instead?

Let’s see what sort of shenanigans those whacky plant estrogens from soy get themselves into.

From the CDC’s latest “National Report on Biochemical Indicators of Diet and Nutrition”:

  • “[S]tudies of children who had been fed soybased formula as infants and who were followed through adolescence (Klein 1998) and young adulthood (Strom 2001) found no adverse reproductive or endocrine effects.”
  • A meta-analysis of 32 studies in which adult men consumed soy foods, isolated soy protein, or isoflavone extracts (from soy or red clover) found that neither soy foods nor isoflavone supplements alter measures of bioavailable testosterone concentrations in men (Hamilton-Reeves 2010).

From Harvard Medical School:

  • Although phytoestrogens are chemically similar to estrogen and behave like the hormone in some respects, they are far weaker. Men don’t need to worry about feminizing effects from eating soy-based foods.

From Today’s Dietitian magazine:

  • The claim that “Soy causes feminization in men” is one the top 5 myths about soy.

From the journal Fertility and Sterility:

  • “Soybean isoflavone exposure does not have feminizing effects on men

Also from the journal Fertility and Sterility:

  • meta-analysis of 50 studies found that soy has “no effect” on testosterone levels. 

From the the journal Cancer Epidemiology, Biomarkers & Prevention:

  • In comparing a control group to a group of men that added soy milk to their diets for eight weeks, researchers found that the group that added soy milk had lower levels of a type of estrogen (estrone), while levels testosterone stayed the same. “There was a significant difference between the two groups in terms of changes in serum estrone concentrations, which tended to decrease in the soy-supplemented group and increase in the control group over time. None of the other hormones measured (estradiol, total and free-testosterone, or sex hormone-binding globulin) showed any statistical difference between the two groups in terms of patterns of change.”

From Oregon State’s Micronutrient Information Center:

  • Claims that soy food/isoflavone consumption can have adverse effects on male reproductive function, including feminization, erectile dysfunction, and infertility, are primarily based on animal studies and case reports. Exposure to isoflavones (including at levels above typical Asian dietary intakes) has not been shown to affect either the concentrations of estrogen and testosterone, or the quality of sperm and semen. Thorough reviews of the literature found no basis for concern but emphasized the need for long-term, large scale comprehensive human studies.

Uh oh, what “case reports” is Oregon State talking about? Two guys, one 19-year-old, and one 60-year-old guy, both experienced “feminization” of their bodies. They both apparently ate a lot of soy. And they both had case reports published about them. If you’ve read as much anti-soy stuff on the Internet as I have, you know about this dynamic duo quite well.

Before I go on, you should know that, in the world of science, case reports (aka case studies) are considered as being among the least reliable type of evidence of causation. The most reliable type is typically meta-analyses–you know, like the meta-analysis above that found that neither soy foods nor isoflavone supplements alter measures of bioavailable testosterone. I’m still going to discuss these two case studies; I did promise to discuss anti-soy stuff, even if it’s considered highly unreliable in comparison to other types of studies.

First, the case study on the 60-year-old dude from 2008. Men’s Health wrote an in-depth article on it (this article did a lot to spread the soy/man boobs myth). In reading about this case, there are a couple of things that strike me as odd. First, the 60-year-old began doing 2 new things things before he experienced feminizing effects, including moobs: First, he drank 3 quarts of soy milk a day. That’s a ton of soy milk. Think about it. That’s at least 12 cups of soy milk a day. We can all agree that that’s absurd, right? That’s more soy milk than seems humanly possible. And to be doing that consistently, every single day? I assume his story is completely unrelatable to 99.9999999% of the world.
Under his doctor’s orders, he stopped drinking the 3 quarts of soy milk a day and replaced it was lactose-free dairy milk. Problem solved, right? Nope. His breasts started growing and hurting again.

The second big dietary change the 60-year-old made is he had become obsessed with a product called Ensure. Only after he got rid of Ensure did his breasts normalize. (And for the record, his breasts did normalize. A lot of people with moobs have them constantly. So, if soy was a cause of his man boobs, it’s reversible.) persistently. But again, his moobs didn’t go away until he stopped consuming Ensure.

So what’s up with this Ensure product? Well, Ensure contains soy protein. A-ha!

But if you look at Ensure’s ingredients (and by all indications, its formula hasn’t significantly changed since 2008, when this case study was published), soy protein is the sixth most predominant ingredient. What’s the fourth most predominant ingredient? “Milk Protein Concentrate.” In summary: this man stopped consuming soy milk, but his man boobs grew while he was gulping down lactose-free cow’s milk with Ensure, a product that’s fourth biggest ingredient is milk protein concentrate. Plus, the guy was at an age where testosterone levels are known to drop for all men, regardless of diet.

Why isn’t this a case study showing the link between dairy and man boobs?

In any event, even the case study author noted that this is a “very unusual case of gynecomastia [aka man boobs] related to ingestion of soy products.”

What’s also missing from the discussion about the 60 year old is the fact that he’s well, 60. As I said towards the very beginning of this article, one of the biggest causes of man boobs is simply aging. As I’ll elaborate more on in a bit, testosterone production declines as men age, and man boobs become more common for people in that age bracket. It has nothing to do with soy. It’s just a reality of reaching middle age.

The other case study is a 19-year-old guy in 2011. If you thought the 60-year-old was consuming a lot of soy (12 servings, per day, every day), this guy was eating the equivalent of 14 servings of soy per day, every day. Who are these people?! Imagine consuming 14 servings of anything, every single day, each day. We’re talking massive, almost unimaginable amounts of soy. On top of being a soy addict, the 19-year-old was also a Type-1 diabetic, which is a condition that’s associated with low testosterone, and depending on how long he’s had the condition, might be a contributing cause to man boobs. To be clear, the 19-year-old did not develop man boobs; but he did have lower testosterone and loss of libido. For what it’s worth, a report in the British Journal of Cancer Research found that vegan men have significantly more testosterone than meat eaters. The case study authors did not mention that, not did they mention the potential role his diabetes may have played.

In both case studies, these guys were consuming huge amounts of soy. Like, amounts that I couldn’t possibly imagine sustaining every single day, like they did. What would happen to your body if you drank 12 or 14 cups of dairy milk a day? Heck, you can consume too much of anything and have awful health outcomes. People have gotten very ill from drinking too much water. You could eat too much spinach and get sick. Spinach! Is nothing sacred?

This raises an important question. What is a “serving” of soy. Registered dietitian Jack Norris came up with a guide for determining what a single “serving” of soy looks like:

  • 1 cup of soymilk
  • 1/2 cup of tofu
  • 1/2 cup of tempeh
  • 1/2 cup of soybeans
  • 1/2 cup of soy meats
  • 25 mg of isoflavones
  • 8 to 10 grams of soy protein

Compare that last bullet point to the NIH’s recommended daily allowance for protein for men: it’s 56 grams per day. 12 servings of soy (like the 60 year old consumed) equates to 96 to 120 grams of protein. 14 servings (like the 19 year old consumed) equates to as much as 140 grams of protein per day. So, to match how much soy protein these two guys were eating, you’d literally have to eat more than double the NIH’s recommended daily allowance of protein.

What’s really unfortunate is that these two unreliable case studies, with guys eating 100+ grams of protein from soy alone, are at the crux of the anti-soy/soy-causes-manboobs argument. Basically any source that makes that claim points to these two case reports. It’s their best evidence. As I mentioned earlier, Men’s Health wrote a huge article about the 60-year-old guy a few years ago. And the 19-year-old guy didn’t even have man boobs! Even if soy played a role in their feminizing issues, who the heck is eating that much soy?!? Let alone, doing that every single day?!

Sorry, I can’t drop this point. Try to imagine what 12 or 14 servings of soy every day would look like. Even if you binged on soy meats, you would have to eat 3 entire blocks of tofu every single day to match their intake. Or 12 vegan hot dogs, per day. Actually, more like 24 vegan hotdogs per day. Why 24 hot dogs and not 12 or 14? Because there’s another piece of the story that’s missing here that is very relevant to vegan protein: Nowadays, many vegan meats either don’t have any soy at all, or they are a mix of soy and other proteins!  


“Soy meat” is arguably an obsolete term. There are tons of new vegan meat companies on the scene, along with many of the long-time staples of the “vegan section” of the supermarket. If you look at their product line (which, by the way, has gotten more delicious than ever before) you’ll notice many products either have only some soy, or no soy at all. Here’s a sampling of popular vegan meats.

  • Tofurky‘s hotdogs: 80 calories and 11 grams of protein in a single hot dog. And most of that protein is from pea protein and gluten. The same goes for their deli slices–most protein comes from gluten, not soy.
  • Lightlife‘s deli slices: more than half of the protein comes from gluten, not soy
  • Beyond Meat‘s products either have no soy protein at all (like their 20g protein Beyond Burgers, which made from pea protein), or their products are a blend of soy and pea protein
  • Field Roast, which makes delicious sausages, hot dogs, meat loafs, and cheeses–their protein comes from gluten, not soy
  • Gardein‘s amazing products are mostly a blend of soy and gluten.

And to diffuse any confusion, peas and gluten appear to barely have any measurable amounts of phytoestrogen. So, most of the vegan meats of 2017 are almost definitely far lower in phytoestrogens than the “soy meats” of yesteryear.

On that same note, even when you see soy protein “isolate” or “concentrate” on an ingredients list, it may have been processed in a way where the vast, vast majority of phytoestrogens are removed. As explained by Oregon State‘s Micronutrient Information Center, “Soy protein isolates prepared by an ethanol wash process generally lose most of their associated isoflavones . . .” Which companies use ethanol washes to process their soy? I’m not sure. I’ve actually emailed a few, but their responses were by customer service reps who don’t give complete answers. As an aside, I’m not sure why companies choose one process over the other when making soy concentrates and isolates. That’s a topic for another day. Isn’t this post long enough already?


Another related concern and myth espoused by some anti-soy people is the claim that you should be worried about phytoestrogens and soy because “OMG THERE IS SOY IN EVERYTHING!” But the “soy” that’s in everything are soy ingredients that barely have any phytoestrogens in them–soy oil, soy sauce, and soy lecithin.

When people talk about soy being in “everything,” these are the ingredients they most often mean. But again, there’s barely any phytoestrogens in any of those ingredients. Plus, even if for some reason these ingredients did contain some phytoestrogens, they’re rarely the main ingredient in the foods and products that use them. They’re usually one of the last ingredients listed because they’re used in very small amounts. I’m not saying you should start pouring soy oil over everything–but it’s a distraction from things that actually have significant quantities of phytoestrogen.

So, when you’re reading another blog about the dangers of “estrogens” in soy, and it warns you that “soy is in everything,” whoever is saying that probably has no idea what they’re talking about.


Phytoestrogens were first discovered in 1951 when red clover plants were found to be making sheep infertile in Australia. Those clovers have the same type of phtyoestrogens as soy. Scary . . . until you realize that clover is so loaded with that phytoestrogen (genistein), that a human would have to eat 800 pounds of tofu a day to match the phytoestrogen intake that sheep were taking in.

I don’t know too many veggie meats made with red clover. And other than maybe a certain 60 year old and 19 year old I know of, I don’t know anyone in our planet’s history who’ve come anywhere close to eating 800 pounds of tofu per day.

There are other types of phytoestrogens. There’s one type called “lignans” that are found in significant quantities in flax seeds and sesame seeds. Without going too deeply into lignans, I found no evidence connecting lignans with any feminizing effects. A lot of other fruits, vegetables, seeds, nuts and beans have tiny amounts of phytoestrogens. But those other plant-based foods have such tiny amounts of phytoestrogen that they shouldn’t crack the radar.

There’s one exception to that. Obviously, it’s not soy, which I’ve explained is not a cause for worry. And it’s not the lignans in flax or sesame seeds. Fellas, hold onto your moobs–you aren’t going to like this. There’s a phytoestrogen that’s 50 times more potent than genistein (the phytoestrogen from soy), and it’s highly absorbed. The phytoestrogen is called 8-PN. And it’s found . . . in beer. And unlike soy, reputable man boobs websites (there are actually reputable man boobs websites) list beer (and/or alcohol) as a legitimate cause of man boobs. More on the alcohol/manboobs connection in a minute.


This brings us back to one of the main points of this post–what actually causes man boobs? Man boobs actually have a scientific name. It’s called gynecomastia. There’s also a similar condition called pseudogynecomastia. Pseudogynecomastia is when you get man boobs because of increased fat deposits in the chest as a result of being overweight. So, for at least some people, their man boobs could simply be excess fat in their chest from being overweight.

Gynecomastia is when you get man boobs because of the enlargement of glandular tissue in the chest, usually caused by imbalances of the hormones estrogen (too much of it) and/or testosterone (too little of it). Unlike pseudogynecomastia, this type involves glandular tissue rather than fat. What makes this a little extra confusing is that fat cells and being overweight can also promote the hormonal/glandular type of man boobs.

Whether someone’s man boobs are from being overweight (fat), or hormone imbalances (glandular), or a combo of both–what you eat can play a role in both types.

When it comes to hormone imbalances, we’ve seen in this blog post that soy gets an unfair rap. So what legitimately causes these hormone imbalances in men? Fortunately, there are a bunch of academic sources that sum things up nicely. And, when you look at these lists, eating normal amounts of soy is nowhere to be found.

The two biggest causes, frustratingly, are nothing you, or anyone else, could’ve feasibly prevented: hormone imbalances as a result of living through puberty or middle-age.

1. It came about during puberty and hasn’t gone away. Going through puberty causes your hormones to get out of whack. So a lot of guys in their teens develop it. For most, their man boobs vanish. Unfortunately, it sticks around for some people, and according to many sources, this is the single most common cause of man boobs in adults: man boobs that came about during puberty and never went away.

2. It came about during middle age. Testosterone production dwindles in men as they age, causing an imbalance in hormones. That’s probably why you sometimes see commercials for middle aged men with ‘Low T.’ (T = testosterone).

Those are the two biggest causes. Most of the rest of the main causes are about substances that men might encounter in their day to day lives.

And to illustrate these other causes, think of your friend Billy the Bro, a character whom I just made up. Billy is not an AvocadBro–he doesn’t understand why anyone would go vegan, and even if he did, he says he avoids soy like the plague because he heard it has weird chemicals that turn people into effeminate sissies with man boobs. Billy, meanwhile, doesn’t question the ingredients of any of the other foods and drinks he consumes, especially meat, cheese and beer. Still, he’s convinced his mild case of man boobs is from a veggie hotdog he ate a few years ago. Billy should know, what else could have caused it.

3. Alcohol (especially beer). Billy loves craft beer. Bourbon with his buddies. Wine with his girlfriend. Billy doesn’t love the fact virtually every reputable list of what causes gynecomastia has alcohol on it. Why though? One theory is what I mentioned earlier: the phytoestrogens in alcohol (and from the cogeners in alcohol) are so particularly potent—especially the phytoestrogen found in beer (8-PN), which is so strong that it stays in the body for days after drinking beer. It’s acts very differently in the body than soy by binding to receptors that promote breast growth (as mentioned earlier, soy has been found to have the opposite effect in the breast area). In fact, 8-PN is used in supplements that promote breast growth! And studies show that simply drinking moderate amounts of beer provides the same level of 8-PN as these breast growth supplements!! Another significant reason alcohol causes man boobs appears to be that alcohol decreases testosterone. On top of that, long-time drinkers produce more estrogen and often have pretty screwed up livers and testicles, both organs play crucial roles in balancing estrogen and testosterone in men, which creates a perfect recipe for man boobs. Binge drinking, even if occasional, appears to really mess up the liver. So next time you take a sip of booze, remember that booze equals man boobs.

4. Steroids and testosterone injections. Billy was messing around on Instagram while his girlfriend was watching the reality show Vanderpump Rules. The episode featured a character named Jax, who was having surgery to remove his man boobs because of “supplements” he took. I’m not saying Jax took steroids; it’s unclear what supplements he was referring to. But Billy and Jax should both know that anabolic steroids are very much linked with man boobs, because injecting yourself with testosterone reduces your body’s natural production of testosterone. Billy the Bro took steroids for a few weeks to beef up in the gym, and he’s got the muscles and man boobs to prove it.

5. Medications. I’m not going to raid Billy’s medicine cabinet to see what prescriptions he’s on, but propecia, spirolactone, certain antidepressants and antibiotics, and many others, are linked with man boobs. Same with adderall, vyvanse and ritalin. These last few are all “amphetamines” and amphetamines are linked with man boobs. Billy had an adderall prescription during college, yet he blames soy, which he never eats, on his moobs.

6. Skin care products with lavender and tea tree oil. This area is controversial, but many of the leading sources mention the possible link between man boobs applying these specific herbal oils to your skin. For what it’s worth, Googling this possible cause will result in a lot of criticism for the studies behind it. If there’s a link here, it’s weak. Billy’s body wash has both lavender and tea tree oil in it.

7. Marijuana. I’m sorry. But it’s listed on basically every reputable man boobs website. Billy smokes at least a couple times a month.

Other possible causes?

These are possible I haven’t found directly mentioned in the leading gynecmoastia resources, but, for reasons you’ll see, should probably be mentioned in the larger man boobs conversation.

8. Other hormones. There are other hormones that could play a role in man boobs as well. Like IGF-1, according to this study, which found an association between IGF-1 and gynecomastia. And what increases IGF-1 in humans? Animal protein releases IGF-1 in the blood stream, (see: this study), and vegan proteins appear to decrease the concentration.

There’s also cortisol, known as the ‘stress hormone,’ which may play a role. It’s often said that increased cortisol levels lead the body to store fat to protect internal organs in the abdomen, including potentially the chest–but the only evidence I found of that is the connection between cortisol and visceral fat (which isn’t noticeable like subcutaneous fat).

9. Eating fatty food raises estrogen levels, according to some studies. Although it may also increase testosterone, at least according to that study.

10. Having fat on your body apparently increases estrogen, and throws your hormonal balance out of whack. According to Harvard Medical School, “It’s appropriate to think of fat as an endocrine organ or gland, producing hormones and other substances that can profoundly affect our health . . . [I]t’s becoming clear that excess body fat, especially abdominal fat, disrupts the normal balance and functioning of these hormone.” Not surprisingly, weight gain causes testosterone levels to drop.

So what’s missing from this list?


In case I haven’t said it enough: soy is nowhere to be found as a cause of man boobs on almost all of these reputable man boobs info websites. Not the University of Maryland Medical Center. Not the Mayo Clinic. Not WebMD. Not Princeton. Not the University of Rochester. Not Johns Hopkins. One source, the American Academy of Family Physicians, mentions the link between eating 300 mg of isoflavones (aka 12 servings of soy, per day) – as a risk factor, citing those case studies of the two guys who ate absurd amounts of soy. However, that publication was made in 2012–their latest patient info pamphlet no longer mentions soy.

How do you get rid of man boobs and reduce estrogen and increase testosterone?

None of this is medical advice, but it summarizes what studies appear to show. As I said towards the beginning of this post: the first place you need to go is a medical doctor.


  1. Eat more fiber. “There is longstanding evidence that dietary fibers may reduce circulating estrogen levels through changes in the gut microbiome and increased excretion of estrogens in the gastrointestinal tract.” (Fun fact: fiber is not found in any animal foods. It’s found ONLY in vegan foods, like vegetables, beans, fruits and grains).
  2. Eat plenty of carbs. Studies link eating carbohydrates with higher testosterone and lower cortisol.
  3. Eat moderate amounts of soy, because it has anti-estrogenic effects.
  4. Avoid alcohol (especially beer), because it contains a potent type of phytoestrogen that is absorbed in the colon.
  5. Avoid dairy, cheese and milk–which are the biggest source of dietary animal estrogens. Remember, dairy products come from lactating mother cows that are teeming with female hormones. Replace butter with olive oil, which has a compound found to increase testosterone.


  1. Lift weights. It apparently increases testosterone.
  2. Lose fat. Because fat cells produce estrogen.
  3. Reduce your cholesterol. Having high cholesterol may have an estrogenic effect.
  4. Reduce stress. Make sure to meditate and relax. Stress increases cortisol. Cortisol decreases testosterone. Cortisol triggers your body to deposit fat.
  5. Get plenty of sleep. Low quality sleep decreases testoerone.

Yo Soy Avocadbro

It took me a while to put it all out there, but hopefully now you’ve seen that the soy/man boobs connection is very much unfair and unwarranted. To prove that the myths and unfair criticisms of soy aren’t mere straw-man arguments, take a look at this reddit thread. The topic is “What is a relatively inexpensive snack that could be munched on continuously for about 2-3 hours without ruining your health?” It generated a ton of responses. (Side note: nearly all of the responses were vegan!)

Here are some of the leading responses: Carrots. Pomegranate. Cucumbers. Sunflower seeds. Celery. Wasabi covered nuts. Dried coconut strips. Fruit salad. Dried fruit. Homemade vegetable chips. Air popped popcorn. Grapes. Rice wafers. Almonds. Peas. Leafy greens. Pistachios. And so on.

Someone also mentioned edamame (aka cooked soy beans). Unlike most of those other snacks, this one generated a lot of follow-up conversation. “Too much estrogen ain’t good for ya,” said a first person. Fortunately, a bunch of people chimed in to say that that claim is a “myth” or “pseudoscience.” Then, the first person who made the original scare claim then edited their post to say that soy “seems pretty safe actually.”

But then someone else heard that phytoestrogens were discovered because sheep are much more fertile when they eat red clover, and that there’s clearly established link of the effects phytoestrogens have on animals. Does that ring a bell?The red clover-eating sheep were eating the equivalent phytoestrogens as is in 800 pounds of tofu. As registered dietitian Jack Norris, RD, states: “There are other isoflavones [other than those found in soy], the most studied of which are the isoflavones in red clover. These are not the same isoflavones as found in soy.”

Then someone seemed to recall that soy causes problems with memory and concentrating. Although, according to Jack Norris, RD, “There have been 12 short-term clinical trials looking at the impact of soy on cognition, and all have shown soy to be helpful or neutral. A longitudinal study found tempeh to be associated with improved cognition. Three reports from longitudinal studies have associated tofu with reduced cognition in some groups, but increased cognition in another group, and neutral in others. This is likely due to confounding. Based on the research to date, there should be little concern about eating soy, including tofu, with regards to cognitive decline.

Why does it seem like everyone has heard of a study on soy that makes it sound worrisome? As Harvard Medical School noted in its Health Letter, “Literally thousands of studies have been done [on soy]. Soy and isoflavones may be one of the most-researched topics in all of nutrition . . .   it’s easy to get lost in a maze of inconsistency and nuance.”

Meanwhile, in that same reddit thread, someone mentioned “Homemade beef jerky.” It was one of the only non-vegan snacks I found in the top comments. Unlike edamame, it barely triggered any side conversations Now, all environmental and animal welfare issues aside, how the heck is homemade beef an easy, affordable snack? If you search for homemade beef jerky recipes, it takes anywhere from 6 to 30 hours to make. That’s not easy. And inexpensive? According to prices I looked at from Peapod and in a random American city (Indianapolis), a single pound of a flank steak will cost anywhere from $10 to $13. And that seems to be if you get the conventional stuff. Pasture raised and without added hormones is another story.

Then there’s the question of whether beef jerky could hurt your health. There were a couple comments by people worrying about sodium and salt content. But no mention of the very real link between beef and heart disease; or beef and cancer; or salting and curing meat and cancerSmoked meat, after all, has more carcinogens. As does meat cooked at high temperatures. Or estrogen exposure and sous vide cooking (even if you use BPA and phthalate free plastic wrap, most plastics still have compounds whose names aren’t as well known as BPA, but are still estrogenic, and are leached when heated or exposed to acidic substances, which is no wonder why sous vide plastic manufacturers are “unwilling to disclose the full formulations and additives.”).

There’s a lot to keep up with. And certainly there’s plenty I missed or didn’t get to. When it comes to soy, despite the thousands and thousands of studies, “a few generalizations can be made,” as Harvard Medical School stated in its health letter. In this post, I unveiled a bunch of those generalizations from all of the reputable sources I relied on.

I’m not a medical professional or a scientist. So none of this is medical advice. However, I believe I can think relatively critically and honestly. If I came across something negative about soy (even if it’s funded by the meat or dairy industry), I tried to make note of it. I’m also open to anything else I learn as time goes on–pro soy or not. I benefited a lot from reading the work and summaries of actual experts and organizations: like the CDC, Tulane University,, NIH,, North Carolina State University, Harvard University, and many others that I linked to throughout this post.

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