Possible health impact of phytoestrogens and xenoestrogens in food

Plants produce estrogen-like substances, denominated phytoestrogens, which are present in many human foodstuffs. The consumption of phytoestrogens has been associated with a variety of protective effects. Their relative estro genic potency combined with their concentrations in food and human plasma i ndicate biological relevance. However, their biological properties differ f rom those of estradiol or other endogenous estrogens in humans. For instanc e, their possible effects on SHBG, inhibition of steroid metabolizing enzym es, anti-proliferative and anti-angiogenetic and other side effects have be en described. Furthermore, phytoestrogens can exert estrogenic and antiestr ogenic activities at the same time and their potency and metabolism have no t been yet elucidated in all cases. In recent decades growing evidence has accumulated on the hormone-like effects of synthetic chemicals that appeare d in the environment. The possible impact of xenoestrogens, to which humans are also exposed through the food chain, needs to be further clarified as well. The molecular effects and control mechanisms of these substances, the ir pharmacokinetics, threshold levels and dose-response differences are iss ues that require further research before a full assessment of their effect on humans can be drawn. Evaluating the total exposure and impact of this es trogenic effect is very challenging because of the lack of specific knowled ge in some areas and the differences in the biological activity among these substances, as pinpointed in this review.