Effects of soy on human reproductionSome scientist have doubts about the adverse effect of soy consumption on human reproduction. High soy consumption may cause harm in the human population via its estrogenic or goitrogenic activities. However they say that more experimental and human research is required before any concusion can be drawn .
Animal studies show that soy phytoestrogens may damage the male reproductive organs. A review study indicates that these phytoestrogens may act as a endocrine disruptor . Researchers at the Johns Hopkins School of Public Health found that pregnant rats a diet laced with genistein may harm the male fetus, possibly affecting future reproduction . A study that made headlines examined the association of soy foods and isoflavones intake with semen quality parameters .
Many studies have demonstrated a possible adverse effect of soy intake on human and animal reproduction. However, these findings have not been confirmed in epidemiological studies. For example, Asians who consume a lot of soy products don't have more problems with decreased fertility than populations with low soy intake.
References Goitrogenic and estrogenic activity of soy isoflavones. Environ Health Perspect. 2002 Jun.
Soy, phyto-oestrogens and male reproductive function: a review. Int J Androl. 2010 Apr.
 Transplacental transfer of the phytoestrogen daidzein in DA/Han rats, Archives of Toxicology, Feb. 2002
 Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Hum Reprod. 2008 Nov.