Effects of protein supplementation on muscle mass, muscle strength, and physical performance in older adults with physical inactivity: a systematic review and meta-analysis.

Abstract

Background: Maintaining skeletal muscle mass and function in older adults is of paramount importance for preserving both quality of life and overall health. Exercise is essential for muscle maintenance; however, for older individuals with comorbidities, engaging in physical exercise may pose challenges due to decreased endurance and the inability to reach optimal exercise intensities. Several studies have investigated the effects of protein supplementation on muscle mass, strength, and physical performance in older adults. However, the results are inconsistent. The objective of this study was to systematically review and synthesize the effects of protein supplementation on muscle mass, muscle strength, and physical performance in physically inactive older adults.

Methods: Four databases (PubMed, EMBASE, Web of Science and the Cochrane Central Registry of Controlled Trials) were systematically searched from inception to 31 January 2025. Two reviewers independently conducted the study screening, data extraction, risk of bias and GRADE assessments. In accordance with the PRISMA guidelines, the outcome data were synthesized using meta-analysis via RevMan5.4 software or a narrative method.

Results: Eight data groups from six randomized controlled trials(RCTs) were included in the analysis, stratifying participants into three physical activity(PA) trajectories: sustained low PA (n= 1), transition to structured training from low PA (n= 4), and a shift from moderate to low PA (n= 3). Protein supplementation had no statistically significant effect on total lean body mass (p> 0.05). Furthermore, secondary muscle mass parameters showed negligible intervention benefits, whereas heterogeneous outcomes were observed across muscle strength and physical performance metrics.

Conclusions: The influence of protein on muscle mass was not significantly efficacious, and mixed results were shown for muscle strength and physical performance. Further well-designed studies are needed to determine the effectiveness of protein supplementation to maximize its potential benefits in older individuals with physical inactivity.

Trial registration: This study was registered at www.crd.york.ac.uk/prospero/(registration no. CRD42024504443).