Eating Soy and Testosterone: Can Regular Soy Consumption Really Cause Low T?

The debate about men eating soy and its hormonal effects has been going on for years, and there are 2 groups in particular who fuel the debate year after year…

1. The group that often contains a lot of vegans and vegetarians, who claim that soy is in fact, a really healthy superfood, and that there’s no science backing up its testosterone lowering effects.

2. The group that usually contains a lot of bodybuilders and gym rats, who claim that soy is the equivalent of eating birth control pills and that it has very powerful testosterone lowering effects in the human body.

But which group is right? Or could it be that both of them are wrong? Let’s find out:

Eating Soy and Male Testosterone Levels

eating soy and how it affects testosteroneThere is really a need for debate like this, because soy is one of the most consumed foods in the world. It’s literally hidden in almost everything that we stick into our mouths.

Just start reading the labels of foods at your house, and you’ll soon see that almost everything has soy in it. The marinade in your meats often contains soy. See that word “vegetable oil?”, that’s more than likely processed soybean oil. Soya lechitin is a filler agent in most processed foods, and as you might guess, it’s a highly processed end-product of soybean production.

It’s so funny how blind we are to the fact that we’re eating a shitload of soy everyday, without actually eating soy. It’s just hidden in everywhere.

Back in 1999 more than 7% of all dietary fats in America, came from soybeans. Over a quarter of all American baby-formulas are made with soy as the base ingredient. And school lunch programs across the country are even adding soy to hamburger patties. That’s just crazy.

Why is soy put into everything then?

1. About 93% of the soy in the U.S is now officially GMO’d (genetically modified). This means that soy is extremely cheap. And cheap is what most of the food manufacturers like.

2. SOYJOY® is one of the leading sponsors of AND (Academy of Nutrition and Dietetics), which is an agency that pretty much dictates how the Americans should eat. No wonder why the governmental food recommendations state that men should eat at least two servings of soy per day…

Well what about the claim of soy reducing male testosterone levels? What is the basis for that?

Answer: Soy contains these compounds called isoflavones (genistein, daidzein and glycitein) which act as phytoestrogens (plant estrogens) in the human body. They’re structurally similar to the principal female hormone, estrogen, and are believed to have similar effects in the body.

As high estrogen level in men are almost always a direct route to low testosterone levels, eating soy – which contains estrogenic compounds – is often blamed for lowering testosterone.

But is that really what happens in the human body? Let’s see what science says:

a) Dr. Kenneth D.R. Setchell from Colorado State University, discovered this small molecule called equol from humans back in 1982. Since then he has been researching the molecule. He has already proven that the compound is formed in the gut when we eat isoflavones, and that men who eat a lot of soy have high amounts of equol present in their blood stream. Back in 2004, Dr. Setchell found out that equol is a strong anti-androgen, which can almost completely shut down the activity of dihydrotestosterone (the most potent androgen).

b) This study followed one 19 year old man who started consuming hefty amounts of soy in his diet. Suddenly the guy lost all interest to sex and suffered from erectile dysfunction. His blood DHEA, testosterone, and DHT levels also plummeted significantly. 1 year after stopping the soy consumption, his erectile health and hormonal profile was fully regained

c) In this human study, from 99 infertile men, the men that ate the most soy had the lowest sperm count.

d) In this study, soy protein increased the number of epithelial cells in the breast tissue by 29% (this is a sign of overblown estrogen).

h) These three animal studies [this, this, and this] found out that the isoflavones in soy can cause breast cancer (another sign of overblown estrogen).

i) In this study the researchers found out that male infant rats who received soybean feed when they were still in womb, had problems in sexual organ developement. This study also found out similar effects.

j) In this study, soy protein decreased testosterone and DHT levels in healthy young men.

NOTE: There are few studies which show no major differences in testosterone levels after soy consumption. However they’re quite often sponsored by SOYJOY® or other large soy producers. Meaning that the results are of no use and often completely biased.

Another thing to note is that dihydrotestosterone is made when an enzyme called 5-alpha reductase converts testosterone into DHT, and as soy lowers DHT, there is actually less testosterone being converted too. Meaning that the reduction in DHT can mask the testosterone lowering effects.


There really isn’t a reason for why men should be eating soy. It contains powerful phytoestrogens and produces equol in the gut which is a strong anti-androgen.

On top of that, does anyone actually like the taste of soy? The only people who eat it are women and men who follow a vegan/vegetarian diets. For men who don’t follow these diets, we tend to eat soy only by accident, as it’s hidden around in so many of our favorite foods.

Anyhow, you should probably avoid soy if you’re a man. It’s not good for us, and it tastes bad.

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Eating Soy and Testosterone: Can Regular Soy Consumption Really Cause Low T? was last modified: July 13th, 2017 by Ali Kuoppala
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