Phytoestrogens adverse effects

Phytoestrogens were first associated with adverse effects on mammalian development and fertility from observations of animals consuming phytoestrogen-rich plants. Ewes feeding on Australian clover developed abnormal plasma concentrations of endogenous hormones with subsequent loss of fertility (Bennett etal.,l 946 Moersch et al., 1967 Obst and Seamark, 1975). 

In some animals, consumption of a phytoestrogen-rich diet can cause temporary infertility and reproductive system disorders (Irvine, 1999). In humans, lower testosterone levels and a decline in human semen quality over the past century have been luiked to increased exposure to environmental endocrine disrupters (EDCs) (Sharpe and Skakkebaek, 1993). Furthermore, cases of sexual impotence have been reported in males exposed to synthetic estrogens in the pharmaceutical industry (Mattison et al., 1990). If this might be the case, the fetal-prepubertal period and Sertoli cell development would be of critical importance (Sharpe and Skakkebaek, 1993). However, an adverse effect of phytoestrogens on male fertility has yet to be proven. Recent work (Mitchell et al., 2001) addressing this point led to the conclusion that up to 40 mg/day of isoflavones over a two-month period had no effects on gonadotrophin and... 

Beneficial or adverse effects of phytoestrogens have to be more rigorously evaluated and long-term studies are necessary for most, if not all, diseases in... 

Assessment of whether a chemical has the potential to cause adverse effects in humans arises usually from direct observation of an effect in animals or humans, such as the acute poisoning episodes that have occurred when potatoes contain high levels of glycoalkaloids. Epidemiological studies have also been used to infer a possible relationship between intake of a particular type of food, or constituent of that food, and the potential to cause an adverse effect. Such observations led to the characterisation of the aflatoxins as human carcinogens. However, natural toxic substances that occur in plant foods have often been identified through observations in animals, particularly farm animals. It was observations of adverse effects in farm animals that led to the further characterisation of the phytoestrogens and the mycotoxins. In other instances, the concern arises from the chemical similarity to other known toxins. 

Whitten, P.L., Lewis, C., Russell, E., and Naftolin, F. 1995. Potential adverse effects of phytoestrogens. J. Nutr. 125 771S-776S. 

Systematic reviews In a meta-analysis of randomized trials of isoflavones, given for menopausal symptoms, adverse events occurred in 2019 of 5502 women taking phytoestrogens (37%) and 1824 of 4806 (38%) who took placebo, a non-significant difference [lO ]. Hormone-related adverse effects and reactions, endometrial... 

---