The problem with this is that "unambiguous, conclusive proof" is an ill-defined benchmark. That's before getting into the question of food allergies or intoler

The problem with this is that "unambiguous, conclusive proof" is an ill-defined benchmark. That's before getting into the question of food allergies or intolerances. I stopped eating meat 8 or so years ago, and I love seitan, but that would be wildly unhealthy for a person with a gluten allergy to consume. On the other hand my meat eating sister is allergic to chicken, and has been told by her doctor to cut down on red meat, so seitan is safer for her than animal products.