Given how incredibly complex human health is, it’s no trivial task to identify precisely how/why some specific behavior is “healthy” or “unhealthy”. Given that predicament, our best guide is what our ancestors did, since it’s passed the test of evolutionary time to at least get us to our present moment. The burden of proof is on any reformer to demonstrate why his reform is better than the tradition.

In the case of something as ancient as meat eating, which is so fundamental to our species as to be reflected in our very physiology (teeth, digestive system), this is an extremely high bar.