Never take anyone on the internet that uses the phrase "burden of proof" seriously.
That being said, veganism is a false diet.
Based upon primates eating habits:
"The diets of nearly all monkeys and apes (except the leaf-eaters) are composed of fruits, nuts, leaves, insects, and sometimes the odd snack of a bird or a lizard (see more about chimpanzees). Most primates have the capacity for eating sugary fruit, the capacity for eating leaves and the capacity for eating meat."
Chicken is a bird
Based upon anthropological research/discoveries:
"UC Davis anthropologist Teresa Steele studied animal bones from the site, showing that our ancestors ate lots of gazelle and other game as well as ostrich eggs."
Lots of meat
Based upon "health" for the eating habits of old nippons:
"It is surely no coincidence that Ikaria only got its first supermarket three years ago, while, in contrast to the centenarians, the generation of Okinawans born since the arrival of the US airbase and its accompanying fast-food outlets have demonstrably declining health.
The Okinawans eat three servings of fish a week, on average.
"All of these diets work on similar mechanisms," Mather tells me. "One hypothesis is that the secret about ageing is to avoid accumulating molecular damage, and eating fish, beans, nuts, seeds, legumes, whole grains, and not so much red meat, dairy or sugar may help us to reduce that kind of cellular damage." Sadly, the professor is dismissive of silver bullets: "In the early days we did try to link health with specific foods or nutrients, but now we look more holistically at dietary patterns."
Veganism is a false diet because humans evolved to be able to outrun any animal on the planet given a suitable amount of time, old people in japan aren't vegetarians and monkeys eat birds and lizards.