Is Soy Safe For Men?

Is Soy Safe For Men?

In recent years, the consumption of soy and soy-based products has sparked a debate within health and nutrition circles, particularly regarding its effects on male health. As a versatile and protein-rich food, soy is a staple in many diets worldwide. 

However, its purported links to hormonal imbalances in men have raised questions and concerns. In this blog, you will delve into the evidence surrounding soy, its impact on male hormones, and the truth behind the headlines.

What Is Soy?

Soybeans are a type of legume native to East Asia, widely consumed for their high protein content, vitamins, and minerals. They're processed into various food items, including tofu, soy milk, and soy protein isolates. 

Soy also contains isoflavones, a class of compounds that can mimic estrogen, the primary female sex hormone. This estrogen-like activity has been the root of many concerns regarding soy's safety for men (R).

Why Is Soy Bad for Males?

The main argument against soy consumption for men stems from the isoflavones it contains. Critics argue that these compounds could potentially disrupt male hormonal balance by increasing estrogen levels and decreasing testosterone levels.

The idea that estrogen negatively affects testosterone levels in men stems from a basic understanding of the hormonal regulatory mechanisms in the human body, particularly the hypothalamic-pituitary-gonadal (HPG) axis, which controls the production and regulation of sex hormones. 

Many believe this imbalance can lead to various health issues. Concerns include fertility problems, breast development (gynecomastia), and compromised masculinity (R).

How Much Estrogen is in Soy?

Isoflavones in soy can exhibit estrogen-like activity but it's important to clarify that they are not estrogen. Their impact on the body is much weaker compared to human estrogen. The actual estrogenic effect of soy isoflavones on the male body is significantly lower than the fear-inducing claims suggest.

To put this into perspective, consuming soy products introduces phytoestrogens into the body, not estrogen. The body's estrogen, such as estradiol, is significantly more potent than phytoestrogens. 

The effect of phytoestrogens is much weaker compared to the body's own estrogen. For instance, the estrogenic effect of isoflavones is estimated to be 1/1000th to 1/10000th of estradiol's potency (R). So, to then answer the common question….


Does Soy Milk Contain Estrogen?

No, soy milk contains isoflavones, which can mimic estrogen but are not the same as the estrogen produced by the human body. The effects are much milder and not comparable to human estrogen. Soy milk contains 6 to 56 mg of isoflavones per 1 cup (R). 



Can Soy Lower Testosterone?

Several studies have investigated the relationship between soy consumption and testosterone levels in men. The majority of this research indicates that soy does not significantly affect the testosterone levels in men. 

A comprehensive review of clinical studies found no conclusive evidence that soy intake affects the concentrations of testosterone in males (R). With that cleared up, men often continue to show concern when consuming particular soy based products. Let's clear up some fallacies. 


Is Tofu Bad for Men?

No, tofu is not bad for men. Consuming tofu as part of a balanced diet does not adversely affect male hormone levels or health, according to current research (R).

Is Soy Protein Bad for Men?

Soy protein, like other soy products, is safe for men when consumed in moderation. It is a high-quality protein source that can be part of a healthy and balanced diet without negatively impacting male hormonal health (R).

Current Research on is Soy Safe for Men

The current research suggests that soy consumption does not have adverse effects on men's hormonal health and may even provide certain health benefits:


🔍 Clinical studies indicate that soy protein or isoflavone intake does not alter testosterone levels, sex hormone-binding globulin (SHBG), free testosterone, or free androgen index (FAI) in men, suggesting no estrogen-like effects on male reproductive hormones (R),
🔍 Soy consumption has been associated with a reduction in prostate cancer risk in men, potentially linked to the type and quantity of soy foods consumed (R).
🔍 A study on Japanese men found that soymilk consumption may modify circulating estrone concentrations, with no significant impact on other measured hormones including estradiol, total and free-testosterone, or sex hormone-binding globulin (R).
🔍 Research has shown that soy protein supplementation can increase serum insulin-like growth factor-I (IGF-I) in men, which is associated with higher rates of bone formation, suggesting potential positive effects on bone health without affecting markers of bone metabolism (R).
🔍 Isoflavone-rich soy protein isolate consumption has been found to suppress androgen receptor expression without altering estrogen receptor-beta expression or serum hormonal profiles in men at high risk of prostate cancer (R).
🔍 Dietary soy has been shown to have both beneficial and potentially adverse cardiovascular effects in men and postmenopausal women. While soy improved blood pressure and lipid levels, it did not improve vascular function, with potential adverse effects noted, such as a decline in endothelial function in men only (R).


In conclusion, to answer the question, is soy safe for men? From current understandings, yes it is. The majority of the evidence suggests that soy consumption does not adversely affect men's hormonal health and may offer benefits in reducing prostate cancer risk and improving cardiovascular health. However, the impact on endothelial function in men may require further research for a comprehensive understanding.

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Written By Natasha Jordan

BHSc Nutritional Medicine, International health - University Of Queensland

Diploma In Dermal Science - AACDS

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