The “Soy Boy” – Myth Or Fact?

Whether you’ve heard the catchy name “Soy Boy” or not, there’s a lot of discussion about the estrogen content of soy and other plant based foods and the possible negative side effects on men’s health. At first glance, there’s a lot of science which shows that increased levels of estrogen in men and worse young boys can damage their ability to develop masculine traits. But what’s the truth here? Does estrogen negatively impact men? Does diet play a role in men’s estrogen levels? or is this all a bunch of internet hype designed to create another “us vs. them” scenario? Let’s take a look.

What are estrogen and testosterone?

So let’s start out pretty basic with an understanding of what we’re talking about. Before we can talk about estrogen and testosterone specifically, we need to understand that both are hormones. Hormones are – in the simplest form, chemicals created by your body that cause other cells, organs and tissues to grow in certain ways. Estrogen and testosterone are the two primary hormones that govern the development of men’s and women’s reproductive systems and secondary sex characteristics. Testosterone is the primary driver for men and estrogen is the primary driver for women. Neither exists alone in a man or woman, but one of the two hormones is more dominant. Men have some estrogen in their bodies and women produce levels of testosterone. It’s actually pretty important that there’s a balance between them. As long as there is a proper balance between the two hormones, then everyone develops as they’re supposed to and the body functions properly.

This is where the concern comes in – when we hear that certain foods contain estrogen, it’s logical to presume that consuming these foods could increase the amount of estrogen in the consumer. If estrogen levels are too high in men, then they may experience infertility, gynecomastia (breast growth) and erectile dysfunction. If women have a high amount of testosterone, then they may experience balding, deeper voice, acne, and increased muscle mass. We don’t focus much on women’s consumption of testosterone because it doesn’t naturally occur in any foods. Certain foods can increase your body’s testosterone production, which we talked about in Testosterone and its effects on muscle growth. However, even if testosterone did occur in food, it seems that our body’s first pass metabolism would filter most of it before our bodies metabolized it.

The dirty secret

From my research there is a dirty secret here, and frankly, one that should be obvious:

The presence of estrogen in the body does NOT decrease muscle mass in men (or women).

I truly thought going into this article that there was a negative link between heightened estrogen in men and a decrease in the ability to grow muscle, which – in hindsight – seems a little silly. I know a lot of really strong women, some of whom could probably bench press me, let alone move around heavy weights. So my initial thoughts seem more than a bit naive to me now. There’s a study by NCBI and an article in Iron Man Magazine that seem to support this as well. The fact is, some studies show that estrogen works in tandem with testosterone to stimulate muscle growth – not to prevent or slow it.

With my naiveté blown out of the water then, what’s the big deal about the “Soy Boy”? Well, there’s still plenty to consider. Remember all of those negative side effects I mentioned? Yeah. Those hobgoblins are still a real issue that can plague a man if his testosterone / estrogen balance goes out of whack.

Things like:

  • Infertility
  • Gynecomastia
  • Erectile dysfunction
  • Slowed Growth

None of these are things that men want to be associated with – nor are they inherently good for us! For a man to develop “normally” his testosterone levels should be around 20 times higher than his estrogen levels. Which takes us back full circle to the original question about the “soy boy” – are foods high in estrogen bad for men?

So why is soy the culprit?


First, why the term “Soy Boy”? Soy is actually the second highest estrogen containing food, with flax seeds topping the list of estrogen containing foods. So maybe it should be “Flax Boy” right? Well, maybe, but soy is present in so many foods that it’s become the focus of the slur. Especially among vegetarians and vegans who may receive large portions of their protein sources from soy products.

What they’re really consuming is phytoestrogens. In normal people speak, that means plant estrogen. When you begin to research soy, you find a whole controversy about whether or not it’s safe for you – links to cancer which are by and large dismissed, to benefits like reduced risk of heart disease. It’s a complex subject that you can learn more about over at Healthline should you be so inclined. However, I’m going to stick with the phytoestrogen component.

It turns out that phytoestrogens are found in many food sources, including:

  • Soybeans and soy products
  • Tempeh
  • Linseed (flax)
  • Sesame seeds
  • Wheat berries
  • Fenugreek (what did you just call me?)
  • Oats
  • Barley

The fact is, many nuts, seeds, fruits and vegetables contain phytoestrogens. So the question becomes, how are these plant estrogens affecting men?

According to our friends at Healthline, Phytoestrogens – and by extension, soy and foods containing soy are safe and in fact may benefit health in the following ways:

  • Reduced blood pressure: Resveratrol and quercetin supplements may reduce blood pressure.
  • Improved blood sugar control: Resveratrol, flaxseed lignans and soy isoflavones may benefit blood sugar control.
  • Reduced risk of prostate cancer: Isoflavone supplements may reduce the risk of prostate cancer, but strong conclusions cannot be reached without further research.
  • Lower cholesterol levels: Soy isoflavone supplements may lower the levels of total cholesterol and “bad” LDL cholesterol.
  • Less inflammation: Soy isoflavones and lignans may reduce levels of CRP, an inflammatory marker, in postmenopausal women with high CRP levels.

While there is some controversy surrounding them (What “health food” doesn’t have some form of controversial swirl around it right?), there’s not much evidence that phytoestrogens have harmful effects on humans – including fertility in men. In fact, some studies also conclude that soy isoflavones (a classification of phytoestrogen) do not change testosterone levels in men at all.

Unlike testosterone, phytoestrogens are not filtered out by our metabolism like testosterone would be. However it looks like there are at least two factors at play that keep phytoestrogens relatively safe for men to consume:

1) It appears that the effects of phytoestrogens are much weaker than the estrogen produced by the body. While they do bind to estrogen receptors, they don’t bind as firmly, so the effects are weaker. Translation – you’d need a lot more phytoestrogens in your body to mimic the effects of naturally occurring estrogen.

2) Not all phytoestrogens are the same. While some may have similar effects on the body to estrogen, others actually block estrogen’s effects.

These two points may explain why there is limited evidence that phytoestrogens have harmful effects, but that’s just my conjecture.

This is all GREAT news for those of us trying to eat healthy. Since phytoestrogens occur in so many foods other than soy – foods that are in fact healthy for you. While more research is needed to conclusively say that there is no need for concern, it appears that – for now at least – the “Soy Boy” myth, at least according to what foods he eats – may be just that – a myth.


Healthline – Signs and Symptoms of High Estrogen

Estrogen Levels and Athletic Performance

Healthline – Risk Factors of Having High or Low Estrogen Levels in Males

NCBI – Mechanisms behind Estrogens’ Beneficial Effect on Muscle Strength in Females

Iron Man Magazine – Muscle Growth and Estrogen

NCBI – Selective estrogen receptor-β activation stimulates skeletal muscle growth and regeneration.

Healthline – Is There a Soy Milk–Estrogen Connection?

NCBI – Phytoestrogens and Their Health Effect

Healthline – Are Phytoestrogens Harmful for Men?

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