Does Soy Really Lower Testosterone Levels? All You Need To Know

Have you stopped eating soy due to the fear that it will lower your testosterone levels? From tofu to smoothies and bars to salads, soy comes in different forms. However, soy’s popularity had dipped due to the news that consuming soy could lead to a drastic reduction in testosterone levels in men.

Now, it’s time to get the facts right. Before delving deep into whether soy lowers testosterone levels, let’s try to understand more about the legume and its constituents.

What Is Soy?

Soybean or soya bean is a species of legume rich in phytic acid, dietary minerals, and B vitamins. A good protein source, soy contains all nine essential amino acids required for the human body to build muscle and support immune function and digestion.

Soy Bean

Also, soy milk and other soy-based products such as tofu contain high levels of B vitamins, potassium, and magnesium.

Soy And Male Fertility

Soy contains a special class of polyphenols known as isoflavones or phytoestrogens. According to a section of experts, since phytoestrogens mimic the female hormone estrogen, they may lower testosterone levels in men. Hence, they suggest that men should avoid soy as it may adversely affect their sexual function. 

Does Soy Really Lower Testosterone Levels?

According to recent research, soy isoflavones and estrogen have very different mechanisms of action. Thus, there is no solid evidence to prove that isoflavone intake adversely affects male fertility or lowers testosterone levels.

  • A research report published on the National Center for Biotechnology Information website in 2010 found that neither isoflavone supplements nor isoflavone-rich soy foods had any effect on total or free testosterone levels, estrogen circulation, and sperm quality. The study also says that isoflavones don’t elevate the risk of erectile dysfunction in males as in the case of the findings reported in animal studies. The reason cited is that the metabolism of isoflavone is different in rodents and human beings.   
  • In 2021, a meta-analysis of 41 studies in Reproductive Toxicology found that soy proteins and isoflavones don’t have any major effect on male reproductive hormones.
  • A large meta-analysis published in Fertility and Sterility in 2010 revealed that neither soy foods nor isoflavone supplements were found to have any effect on bioavailable testosterone concentrations in men of all age groups.

The Recommended Amount Of Soy Intake

It is to be noted that excess consumption of soy will not lower testosterone levels or adversely affect sperm quality. However, according to some studies, frequently consuming soy products in excess quantities can cause some side effects in males.

As part of these studies, different varieties of soy such as soy grits, soy-soymilk, tofu, isolated soy protein, and isoflavone supplements were analyzed. These studies recommend a maximum of 56 g of soy protein per day. 

Having said that, consult with a qualified dietician to check your individualized consumption of soy.

Health Benefits Of Soy

Let’s take a quick look at the health benefits offered by soy.

  • Lowers the risk of heart disease – A good source of unsaturated fats, soy can help balance cholesterol levels and reduce the risk of heart disease. 

  • Cuts down the risk of certain cancers – Experts at the Dana-Farber Cancer Institute say that soy products such as tofu, soy milk, and edamame may help bring down the risk of certain cancers. These include breast, prostate, and gastric cancers.

  • Reduces the risk of osteoporosis – A review of 18 randomized, controlled studies published in the Journal of Clinical Medicine says that soy isoflavones play a role in slowing down the pace of bone loss in postmenopausal women. As a result, it cuts down the risk of osteoporosis.

  • Reduces the occurrence of hot flashes – A study conducted in 2021 proved that a plant-based diet including soybeans was effective in cutting down the occurrence of hot flashes in subjects by 79%. 


Hope you found the article quite helpful in debunking the myth that soy lowers testosterone levels. However, experts warn against the use of isoflavone supplements. The reason is that they may contain much higher amounts of compounds than those found in foods. And, as in the case of all supplements, they are not well regulated by the Food and Drug Administration and they may turn out to be harmful.

About the Author

Nicole Carter is a dedicated and passionate nutritionist, committed to helping individuals achieve their health and wellness goals through the power of proper nutrition. With a Bachelor's degree in Nutritional Science and years of practical experience.

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