Factors influencing the efficacy of nutritional interventions on muscle mass in older adults: a systematic review and meta-analysis

Nutrition Reviews

Oct 2020

DOI: 10.1093/nutrit/nuaa064

Citations:45

Influential Citations:0

Systematic Reviews / Meta-Analyses

Enhanced Details

Methods

Older adults (mean age 78.1 years; SD 2.22; 55.1% female) participated in randomized controlled trials evaluating nutritional interventions on muscle mass. Settings included community-dwelling, hospitalized, and geriatric outpatients. A total of 29 studies comprising 2255 participants were included.

Intervention

Regimens varied across studies and included amino acids (essential amino acids and other amino acids), leucine, L-carnitine, creatine monohydrate, beta-hydroxy-beta-methylbutyrate (HMB), protein supplementation (various sources, sometimes with amino acids), and polyunsaturated fatty acids (PUFAs). Taken orally, around meals; durations ranged from about 2 weeks to 104 weeks; dosages and frequencies varied across regimens; adherence was reported in some studies.

Results

Nutritional interventions had an overall positive effect on muscle mass measures (SMD 0.324; 95% CI 0.186-0.463; P<0.001; I2=72.5%). Significant positive effects were found for amino acids (SMD 0.586; 95% CI 0.181-0.991; P=0.005; I2=60.9%), creatine (SMD 0.633; 95% CI 0.213-1.053; P=0.003; I2=0%), beta-hydroxy-beta-methylbutyrate (SMD 0.522; 95% CI 0.175-0.868; P=0.003; I2=5.4%), and protein plus amino acids (SMD 0.432; 95% CI 0.016-0.849; P=0.042; I2=58.5%). No significant effects were observed for protein alone, protein with other ingredients, or PUFA supplementation. Creatine showed the largest significant improvement among effective regimens. High heterogeneity was present across types except for CR, HMB, and protein plus other. Due to variability in dose, duration, timing, and adherence, the optimal profile remains undetermined. Better adherence generally correlated with positive effects; more high-quality, standardized RCTs are needed to define optimal profiles and assess impacts on strength and function.

Limitations

High heterogeneity across included studies (I2=72.5%) due to diverse regimens and reporting; many studies had unclear risk of bias (notably blinding) and adherence was inconsistently reported; most participants were community-dwelling older adults, limiting generalizability to hospitalized/institutionalized populations; muscle mass was the primary outcome with limited data on strength/physical performance; insufficient data to determine an optimal regimen; need for larger, standardized RCTs and better adherence reporting.

Abstract

Abstract Context Nutritional interventions stimulate muscle protein synthesis in older adults. To optimize muscle mass preservation and gains, several factors, including type, dose, frequency, timing, duration, and adherence have to be considered. Objective This systematic review and meta-analysis aimed to summarize these factors influencing the efficacy of nutritional interventions on muscle mass in older adults. Data Sources A systematic search was performed using the electronic databases MEDLINE, Embase, CINAHL, Cochrane Central Register of Controlled Trials, and SPORTDiscus from inception date to November 22, 2017, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Inclusion criteria included randomized controlled trials, mean or median age ≥65 years, and reporting muscle mass at baseline and postintervention. Exclusion criteria included genetically inherited diseases, anabolic drugs or hormone therapies, neuromuscular electrical stimulation, chronic kidney disease, kidney failure, neuromuscular disorders, and cancer. Data Extraction Extracted data included study characteristics (ie, population, sample size, age, sex), muscle mass measurements (ie, method, measure, unit), effect of the intervention vs the control group, and nutritional intervention factors (ie, type, composition, dose, duration, frequency, timing, and adherence). Data Analysis Standardized mean differences and 95%CIs were calculated from baseline to postintervention. A meta-analysis was performed using a random-effects model and grouped by the type of intervention. Conclusions Twenty-nine studies were included, encompassing 2255 participants (mean age, 78.1 years; SD, 2.22). Amino acids, creatine, β-hydroxy-β-methylbutyrate, and protein with amino acids supplementation significantly improved muscle mass. No effect was found for protein supplementation alone, protein and other components, and polyunsaturated fatty acids. High interstudy variability was observed regarding the dose, duration, and frequency, coupled with inconsistency in reporting timing and adherence. Overall, several nutritional interventions could be effective to improve muscle mass measures in older adults. Because of the substantial variability of the intervention factors among studies, the optimum profile is yet to be established. Systematic Review Registration PROSPERO registration no. CRD42018111306. show less