Association between usual protein intake and muscle function in older U.S. adults: a target-trial emulation using NHANES 2011–2018

Higher usual protein intake was directionally associated with lower odds of mobility limitation among older U.S. adults within a target trial emulation framework, although the primary overlap-weighted estimates were modest and imprecise. Evidence of nonlinearity suggests that intakes near 1.0-1.1 g/kg/day may mark a range where predicted limitation declines more steeply, but uncertainty increases at higher intake levels. Given the cross-sectional design and residual potential for confounding, these findings should be interpreted cautiously. Prospective studies are needed to determine whether sustained protein intake in this range meaningfully preserves functional capacity over time.