Purpose: According to criteria recommended by the European Working Group on Sarcopenia in Older People 2 (EWGSOP2), we analyzed the effects of branched-chain amino acid (BCAA)-rich supplements on muscle strength, muscle mass, and physical performance in older people. Methods: We searched PubMed, Embase, Cochrane Library, and CINAHL from inception until March 2021. Randomized controlled trials that examined the effect of BCAA-rich supplements on older people were included. Random-effects meta-analyses and sensitivity analyses were performed. Subgroup analyses were stratified by participant and supplementation characteristics. Meta-regression analyses were performed to examine the effect of continuous variables. Results: Thirty-five studies were included in this meta-analysis. Quality assessment revealed that 14 of 35 RCTs had some potential bias. The overall standardized mean difference (SMD) in muscle strength, muscle mass, and physical performance between the supplement and control groups was 0.35 (95% CI = [0.15, 0.55], P = 0.0007), 0.25 (95% CI = [0.10, 0.40], P = 0.0008), and 0.29 (95% CI = [0.00, 0.57], P = 0.05), respectively. Subgroup analysis revealed that essential amino acid supplementation improved handgrip strength more significantly than whey protein supplementation in older people. Meta-regression analysis revealed a significant linear relationship between improvements in handgrip strength and body mass index. Conclusions: BCAA-rich supplementation by older people may have beneficial effects on muscle mass and strength. However, the included studies had high heterogeneity, and the results must be interpreted with caution. Prospero registration number: CRD42020206674.
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