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Does Soy Lower Testosterone? (4 Things You Need to Know)

Tyler Sellers
Published by Tyler Sellers | Senior Coach
Last updated: August 3, 2023

As a personal fitness coach, I have seen a lot of vegan and non-vegan athletes switch to soy protein supplements.

There are some benefits from doing this, but in quite a few conversations with my dietitian, she did mention that soy could affect testosterone levels.

I know diet has a significant impact on testosterone levels, but I wanted to find out what science has to say about soy consumption and hormones.

So I spent a better part of the day with my dietitian reviewing studies and trial data on soy-based foods.

Here are our insights.

Quick Summary

  • Soy may lower testosterone in some people, but it depends on their nutrient deficiencies, and their diet.
  • The phytoestrogens in soy may also lower an individual's testosterone levels in the body.
  • Some meals that contain soy protein include tofu, soy nuts, soy milk, edamame, and tempeh.

Does Soy Cause Lower Testosterone Levels?

Close up shot of soy grains and soy sauce

Soy may cause lower testosterone levels, but this mainly happens only in circumstances where people have a poor diet and severe nutrient deficiencies [1].

It may also indirectly affect testosterone due to the phytoestrogens it contains, but more on that later.

The reason there are some misconceptions is that there are some animal studies on mice and rats that have shown lower serum testosterone concentrations.

But in a study with healthy male volunteers, soy protein powder supplementation didn’t have an impact on serum reproductive hormones [2].

The meta-analysis included clinical studies that had a control group and double-blind processes.

What that means is that healthy adult males don’t have to worry about their soy protein shakes causing a low T-count, loss of muscle mass, or erectile dysfunction.

There are some daily recommended limits, but as long as you have a healthy diet and cover all the important nutrients to support androgen concentrations, soy really shouldn’t be a problem.

Connection Between Soy Foods and T-Count

Soy milk inside a glass battle on a wooden table

So, the theory that you hear people talk about all comes down to the effects of soy isoflavones.

Soy proteins contain these molecules that have a similar structure to estrogen [3]. But that doesn’t mean that higher isoflavone intake will cause serum estrogen levels to rise.

And the clinical and biological activity of isoflavone is much weaker than estrogen, which would explain why in the study mentioned in the previous section, there were no measurable impacts on sex hormones in healthy men.

“Isoflavones are plant-based compounds found almost exclusively in beans, like soybeans, that mimic the action of the hormone estrogen.”

- Lindsay Cook, PharmD,

There is, however, one study that reported a minor negative effect of soy on serum testosterone in young men [4].

But you should keep in mind there are many studies that say otherwise, so more research is needed.

What Foods Contain Soy Protein?

There are several types of food that contain soy, and not all of them will clearly state the word soy on them.

Before I give you a list of some of the chemicals that lower testosterone, let me just highlight that the generally accepted safe intake amount for soy is 50 grams [5].

Most men can eat significantly more, but this is a safe amount if you have concerns about low testosterone.

Athletes will most commonly encounter supplements like soy protein isolates, but here are a few other products that contain soy: 

  • Soy nuts
  • Soy milk
  • Tempeh
  • Tofu
  • Edamame

Margaret Stone, founder of Eat Smart, says soy is found in just about everything.

Soy isolate — a lab-created food additive made by extracting protein from soybeans— is usually added to foods to help absorb water, emulsify ingredients and increase protein as a cheap protein source.

As such, she advises to check ingredient labels for anything with "soy"or to look for the soy-free badge.

Can You Counteract the Effect?

A doctor talking to a patient

Yes, you can counteract the effect of low sex hormone concentrations.

The first thing you need to do is take a careful look at your diet and remove all junk food and sugar.

There’s no point trying to tackle low T-levels when it’s your diet that’s causing the problem.

Once you’ve planned out your testosterone-boosting diet plan, it’s time to consider taking the top natural testosterone boosters.

These are typically based on minerals, vitamins, and herbs to trigger your natural production processes.

Ultimately, they can lead to increased muscle mass, improved sexual function, and better mood in a matter of months.


How Much Soy Does It Take To Lower Testosterone?

It would take a lot more than the 50 grams of daily recommended soy intake and an overall poor nutrition diet to lower testosterone.

Drinking soy milk or using soy flour for baking won’t suddenly cause sex hormone levels to plummet and lead to erectile dysfunction.

Does Soy Raise Estrogen in Males?

No, soy doesn’t raise estrogen in males. Neither soy nor the isoflavones it contains have a direct impact on measurable estrogen. The confusion comes from isoflavones having a similar chemical structure to estrogen.

Maintain Healthy Testosterone Levels

If you eat a lot of soy products and your diet is in bad shape, then the first thing you should do is fix your diet. Keep the soy intake to the recommended daily amount, but really focus on important nutrition.

And to gain more health benefits from a higher T-count, consider taking one of our recommended T-boosters for men. These are based on vitamins, minerals, herbs, and amino acids to trigger a natural testosterone production increase.

You’ll be surprised how much of a difference these can make, even in healthy young men.


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