For decades, laboratory animals have lived longer and metabolized more efficiently when certain amino acids were quietly removed from their diets — a finding that now challenges the prevailing wisdom urging older adults to eat more protein, not less. A new review in Cell Press Blue surveys this evidence carefully, tracing the metabolic pathways that amino acid restriction appears to activate, while acknowledging that the distance between a mouse's extended lifespan and a human dietary recommendation is vast and still uncrossed. The science is real enough to take seriously, and fragile enough t