The Soy-Sperm Connection :

Calling all men who want to become fathers! Soy products may reduce a man's sperm count. Based on a recent study, men who consume soy products may have lower sperm counts than those who don't. The study was based on a small group of men who visited the Massachusetts General Hospital Fertility Center from 2000 to 2006

Even though the study found that some of the men who ate soy products on a regular basis had lower sperm counts, the researchers conducting the study are not saying that soy products were the cause of the lower sperm concentrations. The men who had soy products in their diets recorded lower sperm counts than those that didn't, but their counts were still within the normal range.