Protein-Based Strategies and Mediterranean-Style Diets Show the Most Consistent Benefits for Sarcopenia in Older...

Sarcopenia - age-related loss of skeletal muscle mass, strength and physical performance - affects 6-22% of adults aged ≥65 years and is a leading driver of disability and mortality. Evidence on nutritional strategies is fragmented across single nutrients, whole dietary patterns and the emerging gut-muscle axis.

To synthesize evidence on dietary strategies for sarcopenia prevention and management in adults aged ≥60 years, spanning single nutrients, oral nutritional supplements (ONS), whole dietary patterns and gut microbiota-targeted interventions, using a unified Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 and Synthesis Without Meta-analysis (SWiM) framework.

The protocol was pre-registered on the Open Science Framework (OSF; DOI: 10.17605/OSF.IO/WRNZH). PubMed/MEDLINE, Scopus and Web of Science were searched from January 2010 to April 2026. Two reviewers independently screened records in Rayyan, extracted data and appraised risk of bias using Cochrane Risk of Bias 2.0 (RoB 2), Newcastle-Ottawa Scale (NOS), Joanna Briggs Institute (JBI) checklist and A Measurement Tool to Assess Systematic Reviews (AMSTAR) 2. Findings were synthesized using Synthesis Without Meta-analysis (SWiM) and graded with a Grading of Recommendations Assessment, Development and Evaluation (GRADE)-style framework.

Of 2,543 identified records, 248 studies were included (236 primary studies; 12 systematic reviews/meta-analyses): 100 RCTs, 62 cohorts, 68 cross-sectional, 3 case-control and 3 quasi-experimental studies. Among RCTs, a beneficial direction of effect was reported in 84% of single-nutrient trials (particularly protein/leucine and vitamin D ≥800 IU/day), 75% of whole-diet trials and 78% of gut-targeted trials; across all study designs combined the corresponding direction-of-effect proportions were 70%, 65% and 62%. These proportions describe the direction of effect only and should not be interpreted as intervention success rates. In observational studies, Mediterranean and MIND-style dietary patterns, higher protein quality and dietary fibre were inversely associated with sarcopenia incidence. Gut-muscle axis interventions showed a favourable but heterogeneous direction of effect, with low-to-very-low-certainty evidence, via short-chain fatty acid (SCFA) production and enrichment of Akkermansia and Faecalibacterium.

Evidence supports a hierarchical but certainty-graded model. Protein-anchored strategies (≥1.0-1.2 g/kg/day, leucine-enriched, paired with resistance training) and vitamin D repletion in deficient older adults are the most robustly supported (moderate-to-high certainty) and align with existing guideline thresholds. Mediterranean-style diets provide population-level protection (moderate certainty, largely observational). The gut-muscle axis is an emerging fourth pillar (low-to-very-low certainty) requiring large-scale standardised trials before clinical adoption. Recommendations are restricted to the general aging population (≥60 y); prescriptive gut-microbiota targeting is proposed as a research priority rather than current practice. Heterogeneity in diagnostic criteria and outcome reporting remains the key barrier to firm clinical recommendations.