Many people have allergies or intolerances that make it hard to digest soy. But even if you’re not one of them, soy protein isolate may make your stomach rumble. This is because SPI has a higher concentration of trypsin inhibitors, chemicals that reduce available trypsin—an enzyme that helps digest protein—in the body.
So what to do if you’re a soy-loving vegetarian? Skip products with SPI and opt for “natural, whole protein sources like beans, lentils, nuts, and seeds, and organic, non-GMO natural sources of soy like edamame, tofu, and tempeh.”