Jeffrey Bland, PhD argues that the biochemical composition of plant seeds—which is altered by agricultural practices such as use of NPK fertilizers—affects the immune systems of animals and humans that consume those seeds. He illustrates with corn fed to cattle versus wild maize, claiming different seed histories send different signals to consumers' immune systems.
We as human beings depend upon the seeds of plants for the majority of our nutrition, and those factors that are incorporated within those seeds influence the immune system of those individuals that consume those seeds. If you feed a lot of corn to cattle, then you get whatever that information was with the corn's immune system. And if it was ground up ready corn, and it had been treated with NPK fertilizers, you're going to have a different set of immune system characteristics in that corn than wild corn of maize that came through our Central American ancestors, and that's going to signal to those that eat it a different message to their immune system.
