The Effect of Oral Pure Branched-Chain Amino Acid Supplementation on Exercise Performance and Body Composition: A...

Branched-chain amino acids (BCAAs) are an increasingly popular sports supplement used by athletes as they are advertised to increase endurance, muscle recovery, lean muscle mass, and decrease muscle soreness and fatigue. However, the mechanisms behind BCAAs are not well-established, and previous studies have had mostly equivocal results; thus, the possible performance-enhancing effect of BCAAs is controversial. The aim of this systematic review was to evaluate the current literature on the effect of pure BCAA supplementation on exercise performance and body composition. Randomized controlled trials with healthy participants >18 years old were included. The intervention was pure combined BCAA supplements, and the comparator was a matched control. Studies with outcomes related to exercise performance and/or body composition were eligible. PubMed, Ovid Medline, Scopus, Web of Science, and Google Scholar were searched until 15/08/2025. We assessed selection, attrition, performance, detection, attrition, reporting and other biases from low to high risk based on the Cochrane Handbook for Systematic Reviews. Twenty-two studies were included with 511 participants in total. Eleven studies had trained athletes, whereas 11 articles had untrained participants. Daily doses ranged from 1.5g to 82g. The age varied from 18 to 71.7 years, whereas the study length varied from one day to six months. One study found significant differences in body composition after BCAA supplementation. There were 13 studies with significant findings for various exercise performance outcomes such as endurance, strength, muscle recovery, speed, and fitness. The results moderately support BCAA reducing muscle soreness; however, there is inconsistent evidence to support BCAAs having an ergogenic effect on strength and endurance. Due to unclear/high risk of bias in several studies, no meta-analysis was performed. In conclusion, BCAA supplementation may reduce muscle soreness post-exercise, but evidence for improvements in strength, endurance, and body composition remains inconsistent. However, future studies should consider improving certain limitations such as implementing incremental doses, strict diets, and enrolling more participants with diverse backgrounds.