Protein (specially the aminoacid methionine) is actually known to shorten lifespan in mammals. It does this by decreasing the level of FGF-21 in the body. Advices to maximize lifespan should mention restricting dietary protein.
Interesting, I have never heard that one before. Would you mind sharing a source?
You know all those studies on caloric restriction that show life extension benefits? Looks like their benefits are mediated by FGF21 increase resulted by protein reduction [1].