Leucine-Rich Protein Supplements Improve Muscle Strength in Sarcopenia

In older adults with sarcopenia, leucine-rich protein supplementation improves muscle strength and can be suggested as a nutritional treatment, according to study results published in Archives of Gerontology and Geriatrics.

Researchers sought to examine whether leucine-rich protein supplements improve muscle strength, muscle mass, and physical performance in older adults with sarcopenia. They conducted a systematic review and meta-analysis of randomized controlled trials (RCTs). The primary outcome was muscle strength, regardless of the measures that were used. The different measurements had their own variables (ie, handgrip strength, chair stand test, knee extensor strength, arm curl test). Secondary outcomes included muscle mass and physical performance.

Following database searches and full-text review, 6 studies fulfilled all of the quality-related inclusion criteria. These studies, which were conducted between 2008 and 2018, met the inclusion criteria for quantitative analysis. All of the studies defined sarcopenia in older adult participants with the use of established diagnostic criteria, including those of the European Working Group on Sarcopenia in Older People and the Asian Working Group for Sarcopenia.

A total of 699 participants were included in the relevant RCTs. The use of leucine-rich protein supplements was shown to significantly improve patients’ overall muscle strength, muscle mass, and physical performance compared with those in the control group (standardized mean difference [SMD], 0.939; 95% CI, 0.440-1.438; P <.001).

Regarding the primary outcome, statistically significant improvements in muscle strength were reported in the leucine treatment arm (SMD, 0.794; 95% CI, 0.104-1.485; P =.024). Of the secondary outcomes, muscle mass (SMD, 0.763; 95% CI, -0.353 to 1.880; P =.180) and physical performance (SMD, 0.788; 95% CI, -0.010 to 1.586; P =.053) tended to improve in the leucine treatment group; however, the trends were not statistically significant.

No serious adverse events were reported in all 6 studies. Although the supplements were well-tolerated, some participants declined taking the supplements based on their taste preferences.

Several limitations of the meta-analysis should be noted. Only 6 reports were included in the analysis because few studies have actually been conducted that compared leucine-rich supplementation with control interventions in individuals with sarcopenia. The long-term effects of leucine-rich protein supplementation also could not be confirmed as the RCTs evaluated had limited follow-up periods.

The study authors concluded that these findings support the use of leucine-rich protein supplements in older adults with sarcopenia and recommended “a combination of protein supplements and resistance training in this population.”

Editor’s Note: The original version of this article included an error in the confidence intervals of the study’s secondary outcomes; the correct values are 1.880 and 1.586. The article was corrected on August 9, 2022, to reflect this.

Reference

Lee SY, Lee HJ, Lim JY. Effects of leucine-rich protein supplements in older adults with sarcopenia: a systematic review and meta-analysis of randomized controlled trials. Arch Gerontol Geriatr. 2022;102:104758. doi:10.1016/j.archger.2022.104758