Soy, Protein and Growth
The anti-nutrients present in soy and soy food inhibit the digestion of protein. In traditionally made tofu, most of these substances are found in the liquid component of tofu.
Wherever they are found, these compounds can lead to indigestion - mild to severe, As said before they can interfere with protein and amino acid uptake. If eaten frequently and over time these compounds have a negative effect on the pancreas and can even lead to pancreatic cancer..
Soy and soy foods also contain a substance known is a "haemagglutinin."' This substance causes red blood cells to stick together - which is not usual considered a good thing (really never a good thing).
Now both the protease inhibitors (these keep you from digesting protein) and the haemagglutinin are considered growth inhibitors. In the laboratory, rats that are feed these substances fail to grow properly. Are you thinking about the soy meat extender used in the fast food hamburger that your child or loved one is eating? Or maybe the soy cheese extender used in that pizza from the place that delivers pizza with cheese in the crust? Or how about that soy milk?
Again remember that a little traditionally produced soy products will not cause irreparable harm is most people. That said, soy products should not be considered a replacement for meat or a protein replacement but a condiment to be eaten with a rich variety of other nutrient rich foods.