Phytoestrogens are substances of plant origin that structurally correspond to estrogen in mammals. This property allows them to bind to the human estrogen receptor. Phytoestrogens show estrogenic and anti-estrogenic effects. Phytoestrogens are divided into four groups of phenolic compounds: isoflavones, coumestans, lignans and stilbenes. They can be found in legumes, whole grains, seeds, fruits and vegetables. Scientists find that biological effects that phytoestrogens manifest in the human organism are very interesting because many diseases are hormone dependent. Phytoestrogens show beneficial effects in the treatment of breast cancer, cardiovascular disease, prostate cancer, osteoporosis, reducing menopausal symptoms and improving cognitive abilities but also adverse effects such as damage to the male and female reproductive system. However, numerous studies have shown conflicting results, therefore no final conclusion on the effect of phytoestrogens on human health in terms of prevention and treatment of disease can be made.