It’s not hard to find a variety of soy products on our supermarket shelves and specialty stores. Soy milk, soy cheese, soy sauce, soy yoghurt, soy flour and soy protein powders are some of the well-known soy foods.

Soy is often used as an additive in cereals, breads and meat products or as an ingredient in dishes like soy sauce chicken, soy burgers and soy-based infant formulas. In fact soy is hidden in so many of our food products we consume every day even though we’re unaware of it.

So what is soy? Why is there so much controversy around it? And is there any truth to the claim that soy can have nasty effects on our hormones?

What is Soy?

Soy is simply a versatile bean commonly known as the ‘soybean’. The soybean is a specie of legume originating in South East Asia. Soybeans are grown for their many uses in human and animal food and for their source of high-quality protein. In fact it’s the high protein content in soy that makes it a popular choice for vegetarians and vegans. The nutritional content of 100 grams of raw soybeans contains around 420 calories, 36 grams of protein, 30 grams of carbs and 20 grams of fat.

Given the wide range use and popularity of soy therefore begs the question: Why is the ‘wonder bean’ so frowned upon?

Well for all of soy’s great uses and claims of its manifold health and nutritional benefits, there lurks a dark side to the humble soybean.  For guys especially, consuming a lot of soy can have some detrimental effects on our hormone balance and production.

Because soy contains the compounds isoflavones (genistein, daidzein and glycitein) which are a class of phytoestrogens, or plant-derived estrogens, it can exert estrogenic-like activity in the human body. And any substance which promotes estrogen action in men isn’t going to do much good for our androgens.

But is soy really the bean we should banish from our diet less we develop ghastly symptoms of high estrogen, or goodness forbid – man boobs?

Incidental dietary soy intake, that is what we consume each day in the normal course of eating, is probably unlikely to cause issues. But as for the intentional consumption of soy, we could start seeing problems appear if we gobble the stuff down by the carton every day.

There’s a lot of debate about whether soy actually affects hormone health in men. But rather than indulge in such contention, let’s look at what the science says about soy’s role in influencing testosterone and dihydrotestosterone (DHT) levels.

Soy testosterone and the studies  

A study in 2008 showed a strong association between high intake of soy foods and isoflavones with lower sperm concentration in men.

This 2005 study showed significantly lowered testosterone and androstenedione levels among male rats fed a soy phytoestrogen diet compared with animals fed the phytoestrogen-free diet.

A study in 2008 showed the soy isoflavone ‘genistein’ down-regulates androgen receptors.

Researchers of this 2007 study found testosterone decreased by 19 per cent in a group of 12 healthy men aged 25 to 47 years during just four weeks use of soy protein powder.  The soy was also found to act as an estrogen receptor beta agonist which can be cause for health problems in men.

Similarly, this study in 2006 revealed soy isoflavones act as estrogen antagonists regardless of low or high estrogen environments.

This study in 2011 presented a case of a 19 year old type-one diabetic but otherwise healthy man who showed decreased testosterone, DHEA and DHT after ingesting large quantities of soy products while on a vegan diet. The man also exhibited symptoms of hypogonadism, lower libido and erectile dysfunction as a result of his heavy soy intake.

A compelling study on the effects of soy on humans published in The Journal of Nutrition in 2005, showed significant results in the reduction of both testosterone and DHT levels among a group of healthy males aged 20 to 40 years.

For this study, subjects were divided into three groups. One group consumed a milk protein isolate while two other groups consumed soy protein isolates. The soy cohort were divided into low consumption and high consumption soy groups.

Both soy groups showed significant decreases in serum DHT and testosterone compared to the group who consumed milk protein isolate. The results are interesting in this regard as the decreases in DHT and testosterone were significant regardless of low or high soy consumption.

But what of contradictory claims that soy doesn’t cause any decrease in testosterone levels?

The answer to this lies in the soy industry itself.  The Soybean Industry

Soy is a multi-billion dollar industry. Globally, there were 313.05 million tons of soybean produced in 2016. In just the US retail industry alone, soy foods totaled $4.5 billion in 2013, up from $1 billion just 17 years earlier, according to sales data by Katahdin Ventures.

Soy is not only a versatile commodity but cost effective too. For this reason soy has become a major part of our diets by manufacturers who use it as an ingredient in our food products. Soy also has an impressive set of nutritional values that can be spun with persuasive marketing techniques and nomenclature to make it look like a superfood.

In short, the promotion of soy as a healthy food for human consumption is messaging designed by sponsors of soy producers and those with a vested interest in it to keep the gravy train of this lucrative industry booming.

The takeaway here is don’t believe the hype by the pro-soy marketing machine. Excess soy consumption is unhealthy, especially for guys who’d prefer to keep their masculine hormones positively charged.

Five Common Foods that Contain Soy

Everyone knows what soy milk and soy sauce are. We see them almost every time we shop at the supermarket in the packaged milk and sauce aisles.

But what we don’t see are the many other foods and food products that contain soy. This is because some food labels don’t make a show of their soy content, at least not in obvious ways to shoppers.


Miso is a traditional Japanese seasoning. Perhaps great for enhancing the flavor of vegies and meats but bear in mind one of its main ingredients are soybeans, which are mixed with other ingredients and fermented to produce a thick paste for sauces and spreads.


Ever heard of ‘tofu the wonder food’? Tofu is a soybean product made from the curds of soymilk pressed into a block.  It looks like a funny white sponge mass and often promoted for its apparent health benefits. While it is made in a variety of textures it typically comes in one flavor: Bland.


Tempeh is a traditional Indonesian soybean food.  It is often compared with Tofu though it’s more firm in texture. Tempeh is made from whole soybeans mixed with grain and a mold culture which is then fermented and pressed into a block.


When we think of teriyaki we are reminded of teriyaki chicken or teriyaki noodles. Teriyaki is a Japanese cooking technique for meats such as chicken that has been marinated in teriyaki sauce, then broiled or grilled. Teriyaki sauce is made from soy sauce, sake, sugar and ginger.

Vegetable Burgers

Veggie burgers might be the breakfast of vegan champions but a lot of these can pack a hefty amount of soy. Fortunately some veggie burgers are soy-free but others include it as an ingredient in some form – typically soy oil.


Soy is in so many of the foods that it can be hard to avoid. If you want to minimise soy in your diet then be careful to check the list of ingredients on any food product you buy.

While scientific studies have shown that soy decreases androgens and promotes estrogen activity in men, this is usually the result of excessive consumption of soy so there shouldn’t be anything to worry about if it finds its way into your body in the course of normal every day eating.

If you want to keep soy at bay it’s probably best to avoid as much processed food as possible and consume a natural diet consisting of fresh fruit, vegetables and meats. Importantly, watch out for soy in seasoning and oils you add to your recipes.