There are, but everyone has different dietary needs too. Some studies found a genetic sequence evolved in asia that confers better utilization of legume protein. Western Europe and eastern Africa evolved lactose tolerance to get protein instead. Up north people got bigger livers to handle more meat consumption.

I have tried vegan (whole foods only) for months, and I have real trouble with legumes, not just normal gas, and my blood work went crazy. Triglycerides shot up for one.

The healthiest I have ever felt, and the best my blood work has ever been, was eating 1.5lbs of grassfed beef every day (with lots of roots and leaves too).

I can do vegetarian pretty easily, I process eggs and dairy well, but both of those foods are designed to trigger rapid growth in young organisms. I'm not growing anymore so I tend to pack on fat with them.

My chosen middle ground is to get my protein from fish (Cobain said they don't have feelings) and dinosaurs(they had their time). I feel little kinship to cows, grew up around them, but it isn't efficient, even if I feel physically better eating them.

I was vegetarian for six years. But my personal diet has nothing to do with debunking the myth that humans are not omnivores by necessity.

There are plenty of studies showing large populations of vegetarians suffering vitamin deficiencies, so thriving is quite a stretch. Here is one example: https://pubmed.ncbi.nlm.nih.gov/29446340/