Good day, Mr. Jelínek.

I have a question regarding phytoestrogens. You mention that a higher intake can be problematic or even risky for young women and boys in puberty, and the intake of phytoestrogens in men is debatable. What should I understand by the term "higher intake"? For example, concerning soy products - soy cubes, tofu, soy protein - is consuming them 1-2 times a week or less considered higher? Is it better to avoid these and similar products if they are not fermented? Other articles and videos, including those by doctors, claim that we need not fear soy. I don't entirely agree, but I'm looking for an idea of what amounts are considered moderate. Can, for instance, the daily consumption of ground flaxseeds (you mention in the lesson on nuts and seeds that they contain phytoestrogens) in the amount of 20g/day cause problems for men? I ask because I use them together with chia seeds in shakes or even on bread with butter.

Thank you for your response and your time.

This is a good question that is constantly being discussed. Essentially, the whole problem began with the publication of studies pointing out the fact that increased intake of isolated phytoestrogens from soy (in laboratory conditions) led to a higher incidence of certain cancers. This information, in itself, may not be significant because it represents an unnatural situation (experiments on rodents + enormously high doses of isolated substances not achievable through normal diet). In practice, when attempting to prove this effect, interesting correlations were found:

1. The Asian population, where soy products are a regular part of the daily diet, shows an average intake of soy isoflavones around 50 mg per day (equivalent to approximately 250 g of tofu). The incidence of certain cancers (primarily breast cancer), along with other diseases where the positive effects of phytoestrogens are proven, is significantly lower compared to the Western population.

2. The European and American populations show a long-term average daily intake of phytoestrogens around 3 mg, corresponding to the increased incidence of the aforementioned diseases at these substantially lower doses.

3. Phytoestrogens function by having the ability to bind to the estrogen receptor on the cell nucleus membrane. However, this does not increase estrogenic activity to the extent commonly presented because the biological effect of dietary isoflavones is approximately one-thousandth the activity of our own estrogen. This means that under normal conditions, the intake of phytoestrogens from a regular diet is safe (= does not negatively affect hormonal regulation).

4. Problems arise in situations where, instead of a natural diet (soybeans, or whole grains of any legumes, not just soy, or basic derivatives like tempeh or tofu), we incorporate specifically processed soy foods into the diet, resulting in much higher concentrations of phytoestrogens. Typical examples can be soy protein concentrates or soy meat and products made from it. This extreme can also be reached by consuming an enormously high amount of soybeans or their "healthy" derivatives (tofu, tempeh), which can happen in practice as many people tend to follow various dietary trends.

And be careful here—the pro-estrogenic effect of dietary phytoestrogens counters or surpasses the influence of self-produced estrogen, especially in situations where the production of one's own estrogen is significantly lower, which most often occurs in menopausal women. Based on this finding, misinformation spreads that soy is a dangerous food concerning its impact on hormonal regulation, while in reality, it only pertains to very specific situations.
In summary, if you consume basic soy products (= avoiding concentrated sources of phytoestrogens, including dietary supplements) and in quantities that fundamentally adhere to the principles of a diverse and varied diet (= regardless of attempts to quantify exact amounts and seek non-existent boundaries of what is still okay and what is too much), there is no need to worry unnecessarily about the negative impact of phytoestrogens on health. On the contrary, studies highlight the strongly beneficial effects of soy phytoestrogens for both men and women, as they regulate estrogenic activity (for example, their effect on increasing bone density is noteworthy).
The amounts of food you mention are absolutely normal for all population groups; just be cautious of increased intake of protein concentrates.

Themes:  Phytoestrogens