The divide is most often made between carnivore and herbivore. "Shit" flows up, meaning all the nasty stuff an animal eats lower in the food chain, goes up and accumulates in their predators. Carnivore meat is usually more disease ridden and unhealthy for consumption. Our culture has kinda evolved to this point naturally as a protection mechanism.
It's also the reason you should avoid eating too much of bigger fish species due to heavy metals. Smaller fish don't absorb as much, but bigger fish accumulates heavy metal for each small fish they eat.