oy also contains goitrogens - substances that depress thyroid function.o Soybeans are high in phytic acid, a substance that can block the uptake of essential minerals - calcium, magnesium, copper, iron and especially zinc - in the intestinal tract.o Soy phytoestrogens may disrupt endocrine functiono Fragile proteins are denatured during high temperature processing to make soy protein isolate and t