Can Soy Be Harmful? A Thorough Examination
David Janitzek
2026-03-23
3 min. read
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Can soy be harmful? This is a question that's increasingly concerning people. Why? On one hand, we're hearing about its positive effects on the circulatory system, its use in the fight against certain cancers, or its benefits for a woman's body during menopause. However, on the other hand, soy is a strong allergen that can cause severe reactions in some individuals. Moreover, genetically modified soy is controversial and raises concerns about its long-term health effects. Men and people with thyroid disease often avoid soy due to potential hazards. Is there really anything to be afraid of?
Association between soy consumption and male fertility
In the context of soy consumption and male fertility, special attention should be paid to soy isoflavones. They are particularly important during menopause and can have a positive impact on the female body, however, they belong to flavonoids (polyphenols), which are frequently occurring plant compounds. They primarily exhibit antioxidant activity. They resemble female sex hormones - estrogens in structure, hence they are often called phytoestrogens. However, the situation becomes complicated in the case of men. There are concerns that consuming soy isoflavones may have a negative impact on male fertility and cause symptoms of gynecomastia. Research conducted by Czupryńska K., Marchlewicz M., and Wiszniewska B. has shown that phytoestrogens can influence the fertility and sexual development of rats. However, it should be remembered that the results of animal studies cannot be directly transferred to humans. It is also worth mentioning that soy isoflavones interact with estrogen receptors but do not always produce the same response. It is worth noting that in most studies, where men consumed soy in a safe amount (1-3 portions/day), no harmful effect on fertility was demonstrated. However, there are two cases in the literature where hormonal disorders and symptoms of gynecomastia in men were described, who consumed soy isoflavones in an amount of about 360 mg/day, which is approximately 3 liters of soy beverage per day. Such a daily amount of soy consumption is rare even in Asian countries where soy is very popular.
Soybean and its influence on thyroid function
It is an unpleasant reality that there are more and more cases of thyroid disorders. Many people suffer from hypothyroidism or hyperthyroidism. But can soybean consumption have a detrimental effect on the functioning of this important organ? The answer, as always, is complex. Isoflavones present in soybeans can inhibit the activity of thyroxide, a thyroid enzyme involved in the synthesis of its hormones. However, in healthy individuals who do not have nutrient deficiencies, no significant correlation has been found between the consumption of soy and the occurrence of thyroid disorders. It is important to note that soy consumption can only have a negative impact on thyroid function if it is associated with a high intake of antinutrients, malabsorption syndrome, impaired immune system function, and liver problems. It is also important to emphasize that people with confirmed thyroid dysfunction should always monitor their thyroid hormone levels and that people who consume soy should remember to take a break between taking medication and consuming soy, as soy can reduce the absorption of medication.
Soy-induced hypersensitivity
For individuals suffering from food allergies, it is important to realize that soy and its products belong to the group of eight primary food allergens. Apart from milk, eggs, fish, nuts, wheat or seafood, soy is responsible for approximately 90% of allergic reactions. It is worth noting that soy allergens are thermostable, meaning they can be present in heat-processed food products. Currently, investigations are being conducted into a manufacturing process for soybeans that will allow for the acquisition of hypoallergenic beans.
