Food for Thought (in 5 courses) 1) - Humans are heterotrophs - we must "rely on consuming other organisms in the food chain." 
2) Different heterotrophs have developed vastly different digestive and metabolic systems, hence they have different dietary requirements (nutrients that must in their diet).
3) Humanity's diet is already plant-based. Is that a good thing? How well do plant sourced foods (PSF) meet human requirements, @GeorgiaEdeMD? ALL food production has multiple impacts. Are they equal? What standard is used to balance them?
4) Do PSF and animal sourced foods (ASF) have the same metabolic effects in humans? If not, how is that factored into this balancing? Since metabolic derangement is a significant problem, consideration of its correction in dietary/ecological "discussions" ought to be included.
5) What if the vast majority of chronic illnesses (the largest causes of death, worldwide) had a common cause? And what if that were best addressed by eating more ASF and less PSF (especially sugar, seed oils, & starches which make up 60% of US calories, right @tednaiman?)?
Bonus course: Everything we do has impacts. If someone can be healthy on a primarily or exclusively PSF diet, great. Most humans, clearly, cannot. The key to their health and flourishing is to eat more ASF. How to make them accessible & affordable while respecting environment?
Forgot to mention author of paper @PharmacistCath. Sorry.
