Abstract

Isoflavones and their metabolites are termed phytoestrogens because they bind to estrogen receptors, although weakly compared to physiologic estrogens. Soybean is the main source of phytoestrogens. Several recent reviews concluded that there is no evidence that phytoestrogens relieve menopausal symptoms better than placebo. At the same time, some studies suggest their efficacy. In theory, the use of phytoestrogens for hormone replacement appears irrational: biological action of estrogens is receptor-mediated; the question is therefore, why the vegetable analogues should be used instead of physiological hormones optimally complementary to the receptors. Apparently, the problem should be seen within the scope of placebo marketing under the guise of evidence-based medications. For example, a supposed anti-atherogenic effect of phytoestrogens was confirmed by doubtful experiments with cell cultures, which are discussed here. Furthermore, there is a contradiction: phytoestrogens are supposed to compensate for estrogen deficiency in menopause; but at the same time, their estrogenic potential does not prevent the widespread use of soy for infant food and other foodstuffs. Environmentally relevant doses of phytoestrogens have impacts on ovarian differentiation, fertility and genderrelated behavior in animals. In conclusion, the beneficial and potentially harmful effects of phytoestrogens should be clarified by independent research, which can be of importance for the future of the soybean in agriculture.

Key words: phytoestrogens, cancer, soy, isoflavones