Oats contain saponins, which are defense chemicals that may deter animals and humans from eating them.

“so first thing that I have with oats that's a big issue is saponins they're a defense chemical that I'm going to talk about they're also present in things like soybeans and quinoa many grains have saponins they're triterpine glycosides if you want the technical term that make uh soap they make bubbles and they have this saponification quality when they are mixed with liquid but they are defense chemical clearly they're not there for any reason an oats or any reason in quinoa or any reason in soybeans other than to dissuade animals insects humans from eating those things”