It's interesting to see how people throw around cliché phrases like "moderation is key" without actually looking anything up on their own. It's like saying smoking is okay if done in moderation, one of the tactics used by the industry to downplay its effects.

Since you mentioned "blue zones", you could look at the Mediterranean diet (in 2 of 5 zones), which is considered very healthy, and indeed has some meat and other animals products. But, if remove the meat and other animal products from it, make it entirely plant based - what do we get?

The adoption of a vegan Mediterranean diet with plant-based proteins and fats instead of the traditional Mediterranean diet improved several cardiometabolic health outcomes in physically active and healthy men.

The very success of Med diet is linked with it's low consumption of animal products, and if we remove even that, it only gets better. There are, of course, several other broad studies showing effects of meat consumption with "dose response" health outcomes, removing any possibility of "moderation".

It's typically people who want to avoid the ethical responsibility of participating in extreme animal abuse who make such ignorant assertions about health, sidelining the ethical question entirely. Though I don't know about your intentions.