And again as in the oldest person on earth (Violet Brown,117) none of these two cases of super-centenarians are [unsurprisingly] vegans or vegetarians.
For example, there are genetic abnormalities resulting in extremely low cholesterol, no matter how much calories they eat, atherosclerosis will never appear.
Living long is obviously a sign of serious immunity towards all kinds of poisons.
It might mean a lot, though. But it doesn't diminish moral reasons to stay vegetarian.
(Full disclosure: I like meat, but once we have good and cheap lab-grown burgers, I will probably turn into a convinced vegan zealot.)
But to take your point serious: some people already face that problem when deciding whether eating placenta is fine.
I do eat meat, but the immorality of it is obvious.