l4 In
rats, even low level trypsin inhibitor soy protein isolate feeding results in
reduced weight gain compared to controls.15 Soy product producers are not required to state trypsin inhibitor content on labels, nor even to meet minimum standards, and the public, trained to avoid dietary cholesterol, a substance vital for
normal growth and metabolism, has never heard of the potent anti-nutrients found in cholesterol - free soy products.
Trypsin inhibitor content of soy protein isolate can vary as much as fivefold.21 (In
rats, even low - level - trypsin - inhibitor SPI feeding results in
reduced weight gain compared to controls.22) But high - temperature processing has the unfortunate side effect of so denaturing the other proteins in soy that they are rendered largely ineffective.23 That's why animals on soy feed need lysine supplements for
normal growth.