Yes, consuming soy impacts thyroid function--that's the verdict/consensus of the experts...WITH ONE EXCEPTION. What is this exception? FERMENTED SOY. Fermented soy does not impact thyroid function. Fermented soy, and that's generally how the Japanese consume it, does not impede thyroid function. I suppose, though, soy yogurt would be okay, because bacterial culture would cause fermentation. Examples: miso, soy sauce, tempeh...you can even buy fermented soy protein powder. Also re: thyroid and goiterons. Certain foods contain goiterons (check spelling) which are bad for hypothyroid. These are generally cruciferous veggies...which most of us have a problem with (broccoli/cabbage/brussels sprouts, etc.) Cooking releases/negates these goiterons...eating them raw (YAH RIGHT!) does not and therefore negatively impacts thyroid function. So, fermented soy is okay--unfermented soy is nasty for hypothyroid. Incidentally, unfermented and also uncooked soy/tofu impedes thyroid function.