[ip26]

It strikes me as more of an ethical dilemma. I've known quite a few devout vegans who resumed eating animals when their health declined and they could not reverse it without abandoning veganism.

The dilemma being that despite the harm caused, our species developed to eat animal products, and it's difficult to fully replace that.

[jerojero]

That's an interesting point. Some people might really need to supplement their diets with certain animal products, though as far as I know, a vegetarian diet or a diet that includes very little meat consumption is more than enough for most people in terms of health requirements.

Yet that's not really the case, we eat a lot of meat. And red meat as well which really is not necessary in our diets. I believe trying to argue from a naturalist perspective is rather dishonest in that it's by no means the real reason why people consume meat. People consume meat the way they do because it's a cultural expectation as well as a highly pleasurable act for most.

So really, to me, the dilemma has much more to do with how much pleasure are we willing to give up as a society and I really don't think that goes very far. I mean, this debate has also ramifications when it comes to the climate; how much are we willing to give up in comfort and pleasure to curtail the ecological disaster we are causing? The answer: not much really.

In my opinion these are really failings of our political systems, so in other words, the system that's supposed to help us make decisions for our society as a whole. I'm pretty sure most people would agree that maybe in a reasonable amount of time we'd like to see changes to our diets, it's an interesting discussion to have and there could be long term plans to achieve it that could be very much realistic... but our political system simply does not allow the for the discussion to be had in the first place.

[jjtheblunt]

It's primarily about what livers produce, which determines which chemicals are vitamins (which varies across mammals, for example) and which amino acids (the lego blocks that form proteins) are "essential amino acids" for a species.

It's possible as a human to ingest from non animal sources all the essential nutrients, but there's HUGE misdirection in at least american commerce about how to do so. For instance, labels talk about grams of protein, which is inadequate: you could be ingesting a ton of a subset of amino acids in protein, and entirely deficient in an essential amino acid.

It seems that eating animals was a heuristic that supplies essential amino acids and vitamins.

[ornornor]

Just to clarify because it’s not obvious in your comment (but not alluded to either): it is very much possible to opt out of animal cruelty for food and eat a vegan diet while being healthy.