Higher protein intake is associated with lower mortality, and this association is stronger in older adults without chronic kidney disease compared to those with mild to moderate chronic kidney disease, with a 15% greater risk reduction per 0.20 g/kg/d increase in protein intake.

In older adults without kidney disease, the kidneys efficiently remove waste from protein breakdown, allowing the body to use protein to repair tissues and maintain muscle, which supports survival. In older adults with mild to moderate kidney disease, the kidneys cannot clear this waste as well, so excess protein builds up as toxins that damage cells and increase inflammation, reducing the benefit of eating more protein.