According to the Asian Journal of Andrology, scientists in China have found that genistein, a naturally-occurring ingredient of soy beans, interferes with a part of the production of vital enzymes involved in sperm production.
"Excessive exposure to agents that exhibit estrogenic activity may affect male reproductive tract developments and functions." the researchers said, "With regard to this concern, it has been estimated the genistein and daidzein can reach high concentrations in infants who consume large amounts of soy-based products," they added.
The concentrations of genistein used in the study are roughly equivalent to the levels that can build up in the human body following a diet rich in soy products.
Further research is needed to develop a consensus because while some studies have shown adverse effects, other studies have shown no adverse effects.
Bonnie - it is unknown if organic soybeans were used in this study. Conventional soy is loaded with estrogenic pesticides that could skew these results.