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.