No, especially if you only consume normal amounts of soy once or twice a day. Earlier animal studies and poorly controlled human trials suggested that the phtyoestrogens contained in soy protein or supplements can lead to unwanted decreases in testosterone and increases in the more feminine hormone, estrogen. Both of these assumptions have recently been successfully countered by many better controlled human studies. Two meta-analyses (groups of related studies) published in 2010 clearly demonstrate that even very high daily consumption of soy proteins (higher than generally consumed by Asian men) show no significant effects on male hormones. If you enjoy soy-type foods or drinks, do not let this myth stop you. On the other hand, although soy containing foods are generally healthy, the claims made by manufacturers about the extra benefits of soy may not be entirely true.