A new study may help to dispel the commonly held belief that eating soy products can reduce a man's chances of fatherhood.
Soy contains plant compounds known as isoflavones which act like the female hormone estrogen. They can actually bind to estrogen receptors on cells.
"It is perceived that soy can increase estrogen levels, which is why there is a concern that it will have an adverse effect on male fertility," said the principal investigator of the study, Alison Duncan of the University of Guelph. "But we found that consuming soy on a regular basis had no effect on semen quality, which is a direct measure of fertility."
For the study, the researchers recruited 32 healthy males who were asked to consume three different drinks: a soy-protein beverage high in isoflavones, a soy-protein beverage low in isoflavones and a milk-protein beverage. They consumed each beverage for 57 consecutive days. There was a four-week break each time they switched to another drink.
The results, published in the journal Fertility and Sterility, showed their semen volume, sperm count, sperm motility and sperm morphology remained the same throughout the study.
But if soy isoflavones can mimic estrogen, why doesn't their consumption lead to the feminization of males? "The simple answer is that their estrogenic potency or strength is much, much weaker than the estrogen in our bodies," explained Dr. Duncan. "They are 1,000 times less strong."