Sarcopenia, age-related muscle loss, is a prevalent pathology affecting older adults, leading to reduced autonomy, strength, and overall mortality. While exercise and nutritional interventions are common strategies, few studies have examined their combined, long-term effects. This review aimed to evaluate the synergistic effects of exercise and dietary supplementation on body composition and physical function in older adults. The introduction highlights the increasing prevalence of sarcopenia due to an aging population and the limitations of current research focusing on single interventions rather than holistic approaches that combine exercise and nutrition. It emphasizes the potential for synergistic effects and establishes the need for a comprehensive review to understand the combined impact of these therapies.

The literature review summarizes existing research on the effects of exercise and protein supplementation on sarcopenia. It discusses studies showing the benefits of various exercise types (resistance, aerobic, and combined) in improving muscle mass and reducing body fat. It highlights the documented effects of protein supplementation on body composition, but notes a lack of clear evidence regarding its impact on physical function. Existing studies on the use of other supplements like beta-hydroxy-beta-methylbutyrate and L-selenomethionine are also mentioned, emphasizing the need for further research on the combined effects of exercise and diverse nutritional interventions. The review emphasizes that the combined effect of these approaches has not been sufficiently explored, thereby justifying this systematic review.

This systematic review followed PRISMA guidelines and was registered in PROSPERO. Three databases (EBSCO, Scopus, PubMed) were searched using specific keywords. The search was limited to RCTs published within the last 10 years (2012–2022). Inclusion criteria focused on RCTs involving healthy older adults (≥60 years) receiving combined exercise (at least two sessions/week) and supplementation interventions. Exclusion criteria included studies with short duration (<8 weeks), design limitations, lack of control, or inconsistent results. The methodological quality of included studies was assessed using the PEDro scale. Data analysis involved summarizing the characteristics and outcomes of selected RCTs in a matrix. The methodology details the databases used, search terms, eligibility criteria based on the PICO strategy (Population, Intervention, Comparison, Outcome), exclusion criteria to ensure the quality of the included studies, and the PEDro scale used for methodological quality assessment. The process of screening and selecting studies based on abstracts and full texts is also clearly described.

The initial search identified 73 results, which were reduced to 16 RCTs after applying inclusion and exclusion criteria and methodological quality assessment. A total of 1585 participants were included. Most studies used whey protein and vitamin D supplementation. The combined intervention of resistance exercise and protein supplementation (whey protein, essential amino acids) with or without vitamin D showed significant improvements in muscle mass, strength, gait speed, and quality of life. Several studies showed that protein supplementation plus vitamin D was effective in maintaining or gaining muscle mass. While some studies indicated additive effects of supplementation on the benefits of resistance training, others suggested that exercise alone was largely responsible for muscle improvements. The importance of adherence to the combined intervention was highlighted, with better outcomes observed in participants with high adherence. However, biochemical markers showed inconsistent results, with some studies showing improved inflammatory status while others did not. Quality of life improvements were reported in only a few studies. Key findings are organized into sections on body composition, physical function, biochemical markers, and quality of life, each section summarizing findings from multiple studies and highlighting discrepancies or inconsistencies across the studies. Specific examples of studies showing significant positive results and studies where the effects were not statistically significant are presented with references to support the findings.

The discussion section interprets the findings in light of existing knowledge on sarcopenia. It highlights the importance of complete proteins (like whey protein and caseinates) rich in leucine for stimulating muscle protein synthesis. It also emphasizes the role of vitamin D in regulating genes involved in muscle atrophy. The discussion addresses the inconsistent findings on biochemical markers, suggesting that the inflammatory response to exercise might be complex and difficult to interpret. The importance of exercise in restoring sensitivity to anabolic stimuli is also discussed. The discussion section also identifies a limitation of some studies failing to control for exercise versus the combined intervention of exercise and supplementation, and the underestimation of quality of life as a critical outcome in future studies. The review suggests future research needs to focus on adherence to treatment and further investigation into quality of life and biochemical markers.

This systematic review concludes that resistance exercise combined with protein supplementation (with or without vitamin D) is effective in improving muscle mass, strength, and physical function in older adults with sarcopenia. The synergistic effects suggest a beneficial combination therapy, however, adherence to both interventions is key to success. Future research should focus on optimizing the strategies for enhancing adherence and exploring the role of quality of life and other biochemical markers.

Limitations included the heterogeneity of interventions, varying durations, and inconsistencies in the measurement of outcomes across studies. The review acknowledges that some studies lacked a control group for the combined intervention versus exercise alone, making it difficult to ascertain the exact role of supplementation. Furthermore, the limited number of studies assessing quality of life and the inconsistent results for biochemical markers represent limitations. The variability in the types of exercise and supplementation used in the studies also represents a limitation to the ability to make generalized statements.