Low Protein Intake Is Associated with the Risk of Functional Impairment in Older Adults in an Age- and Gender-Specific Manner: A SHARE-Based Study

Background and Objectives: Functional decline and sarcopenia are major aging-related concerns. While protein intake is known to influence muscle health, its longitudinal impact on strength and physical function across age and gender remains underexplored. We assessed whether low protein intake correlate with future onset of low handgrip strength (HGS) and physical impairments in older adults using SHARE data. Methods: We analyzed 38,073 adults aged ≥50 years from 27 European countries using SHARE Waves 8 (2019/20) and 9 (2021/22). A protein intake index was derived from the frequency of consuming dairy, legumes/eggs, and meat/fish/poultry. Low intake was defined as the lowest decile. Logistic regression models, adjusted for age, gender, country, and baseline health, examined associations with low HGS and ten physical difficulties, stratified by age (50–65 vs. ≥66 years) and gender. Results: Low protein intake is associated with higher odds of low HGS in men (OR = 1.39 for 50–65; OR = 1.35 for ≥66) and older women (OR = 1.21). It was also associated with higher odds of mobility-related limitations, including walking 100 m (ORs = 1.25–1.53), stooping/kneeling (ORs = 1.20–1.19 in women), and reaching overhead (ORs = 1.19–1.33). Strength-related tasks, such as pushing/pulling large objects were more affected in men (ORs = 1.44 and 1.21). Notably, women aged 50–65 had over twice the odds of toileting difficulty (OR = 2.27) and significantly higher odds of difficulty shopping (OR = 1.65). These patterns highlight gender- and age-specific vulnerabilities. Conclusions: Low protein intake is associated with modest but consistent increases in the risk of reduced muscle strength and functional difficulties in older adults. Tailored nutritional strategies may mitigate age- and gender-specific risks to physical independence.