In mice, diets with lower protein content are generally associated with longer lifespans, but one study showed the longest lifespan with a diet that was ad libitum and 40% protein.

“so the lifespan studies I think are are are pretty clear that most of the diets where the mice lived the longest were towards the low end in protein but there were some things that I think called into question exactly what was going on there because it wasn't the case that the the mice that were energetic the diets that were energetically lowest gave the longest lifespan as you might expect from caloric restriction and the diet that actually gave the absolute longest lifespan had like I don't know it was like a 40 protein in it right”