Veganism is a form of Atheistic Religious Observance. It's not really about health, it's about setting themselves apart from culture and feeling morally superior to them.
Firstly, one thing to note is that pretty much every religion in the world has dietary laws. Even the loosest forms of orthodox Protestant Christianity will still say drunkenness is a sin, and thus in effect to much alcohol is prohibited (to say nothing of the Protestant Christian sects that prohibit Alcohol, Caffeine, Tobacco or the Catholic prohibition of meat on certain days), and Christianity is notable as being probably the LEAST restrictive on diet. Judaism, Islam, Buddhism, and Hinduism all feature considerable dietary rules and prohibitions. Now, for Judaism at least when you look into the core of their dietary laws they actually make a degree of sense given they originated in the early Iron Age and what we now know about disease and toxins, though the expanded dietary laws that govern if things are Kosher or not end up being... kinda insane.
Regardless, one of the things dietary laws do is create a division between the religious group and those not of the religion*. Further, it allows those who follow the religion to have an immediate and clear way of showing they are morally superior to those that do not. Further they encourage members of that religion to support and eat together and AVOID eating with those outside of the religion, thus keeping them socially within their faith, as one of the biggest bonding and socializing activities that humans do is eating together.
Finally, there always are part of these religious dietary laws that are nonsensical when even when taking into account the moral system that supposedly underlies them (except, again, perhaps Judaism though I'd have to look more at the expanded Kosher rules to be sure), and Veganism has two major prohibitions that fly in the face of their underlying logic of "do not cause harm or suffering to animals": Honey and Wool. Both are prohibited under Veganism, yet both Honey and Wool do not cause suffering to the animals involved (Bees notably will abandoned poorly maintained hives and act in many ways as if they are in a voluntary landlord/renter arrangement, while sheep literally HAVE to be shorn or they WILL DIE, thus it causes MORE SUFFERING to NOT sheer them). However, the underlying point of Veganism isn't the supposed underlying moral imperative, it's to set themselves apart from the rest of society and to feel morally superior to those that do not follow their religious precepts.
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* This is actually one of the reasons Christianity is unusual in that unlike other religions instead of constructing dietary laws, Christianity explicitly REMOVES them, allowing easier sharing of meals between Christians and non-Christians and lowering the cultural cost of conversion to Christianity... perhaps one of the underlying reasons Christianity saw greater success at peaceful conversion than other missionary religions.
We don't have good records of most of those to be able to judge, but both Hinduism and Shintoism have dietary laws, and those are both quite ancient. That said, religious dietary laws pre-Judaism likely were quite similar to Jewish dietary laws as set down in the Pentateuch, where they are more along the lines of proto-food standards than later religious dietary laws. IE, the Jewish prohibition on pork as unclean to eat likely goes to the amount of parasites in port and thus how people who ate pork would sometimes die or get very sick from doing so. Humans are very good at pattern recognition, and thus people consistently eating X and having Y bad thing happen had to have a REASON and since they lacked germ theory or the ability to see microscopic parasites, they assumed that God didn't want them eating it.I don't recall their being any dietary laws in the older pagan religions that predate the Abrahamic faiths
We don't have good records of most of those to be able to judge, but both Hinduism and Shintoism have dietary laws, and those are both quite ancient. That said, religious dietary laws pre-Judaism likely were quite similar to Jewish dietary laws as set down in the Pentateuch, where they are more along the lines of proto-food standards than later religious dietary laws. IE, the Jewish prohibition on pork as unclean to eat likely goes to the amount of parasites in port and thus how people who ate pork would sometimes die or get very sick from doing so. Humans are very good at pattern recognition, and thus people consistently eating X and having Y bad thing happen had to have a REASON and since they lacked germ theory or the ability to see microscopic parasites, they assumed that God didn't want them eating it.
Of the three main pagan religions we know a decent about that are not asiatic ones, Norse, Egypt, and Hellenistic (Romane/China).We don't have good records of most of those to be able to judge, but both Hinduism and Shintoism have dietary laws, and those are both quite ancient. That said, religious dietary laws pre-Judaism likely were quite similar to Jewish dietary laws as set down in the Pentateuch, where they are more along the lines of proto-food standards than later religious dietary laws. IE, the Jewish prohibition on pork as unclean to eat likely goes to the amount of parasites in port and thus how people who ate pork would sometimes die or get very sick from doing so. Humans are very good at pattern recognition, and thus people consistently eating X and having Y bad thing happen had to have a REASON and since they lacked germ theory or the ability to see microscopic parasites, they assumed that God didn't want them eating it.
AIUI, the "primitive Yahwism" reconstructions usually consider it an outgrowth of ritual cleanliness and closely-connected classism, as the archaeology generally suggests waste-feeding in settlements was more typical than open-field grazing but this was typical of the (relative) urban poor and neighboring societies. As such, the mix of it being normal for the "other" as far as the religious authorities were concerned and associated with unclean things hit a remarkably swift preference cascade that nearly completely eliminated pork from diets within about 50 years.I believe the real reason for the pork prohibition comes from environmental factors rather than fear of parasites, Pigs are highly destructive to foliage which is a big problem in a arid climate. The parasite argument was always kind of a stretch IMO because all animals have problems with that and its the reason we cook meats in the first place.