Comparative Efficacy of Different Protein Supplements on Muscle Mass, Strength, and Physical Indices of Sarcopenia among Community-Dwelling, Hospitalized or Institutionalized Older Adults Undergoing Resistance Training: A Network Meta-Analysis of Randomized Controlled Trials

Abstract

Aging-related sarcopenia exerts harmful impacts on muscle mass, strength, and physical mobility. Protein supplementation has been demonstrated to augment efficacy of resistance training (RT) in elderly. This study compared the relative effects of different protein supplements on muscle mass, strength, and mobility outcomes in middle-aged and older individuals undergoing RT. A comprehensive search of online databases was performed to identify randomized controlled trials (RCTs) examining the efficacy of protein supplement plus RT in untrained community-dwelling adults, hospitalized, or institutionalized residents who suffered acute or chronic health conditions. Network meta-analysis (NMA) was performed using a frequentist method for all analyses. Treatment effects for main outcomes were expressed as standard mean difference (SMD) with 95% confidence interval (CI). We used the surface-under-the cumulative-ranking (SUCRA) scores to rank probabilities of effect estimation among all identified treatments. Meta-regression analyses were performed to identify any relevant moderator of the treatment efficacy and results were expressed as β with 95% credible interval (CrI). We finally included 78 RCTs (5272 participants) for analyses. Among the six protein sources identified in this NMA, namely whey, milk, casein, meat, soy, and peanut, whey supplement yielded the most effective treatments augmenting efficacy of RT on muscle mass (SMD = 1.29, 95% CI: 0.96, 1.62; SUCRA = 0.86), handgrip strength (SMD = 1.46, 95% CI: 0.92, 2.00; SUCRA = 0.85), and walking speed (SMD = 0.73, 95% CI: 0.39, 1.07; SUCRA = 0.84). Participant's health condition, sex, and supplementation dose were significant factors moderating the treatment efficacy on muscle mass (β = 0.74; 95% CrI: 0.22, 1.25), handgrip strength (β = -1.72; 95% CrI: -2.68, -0.77), and leg strength (β = 0.76; 95% CrI: 0.06, 1.47), respectively. Our findings suggest whey protein yields the optimal supplements to counter sarcopenia in older individuals undergoing RT.

Keywords: mobility; muscle mass; protein supplement; resistance exercise; sarcopenia; strength.

Figure 1

RRISMA flow diagram of study selection. PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Figure 2

Risk of bias graph crossing trials.

Figure 3

Network diagram illustrating the interconnections among different treatment arms for muscle mass. Each node represents a treatment arm, and the size of the node is proportional to the number of participants assigned to the specific treatment. The thickness of each line is proportional to the number of direct comparisons between arms denoted on the line. RT, resistance training.

Figure 4

Relative efficacy of treatment regimens on muscle mass gain during an overall follow-up duration. Each point estimate (square) presents the network combined effect (SMD) on the outcome measure relative to RC, with the 95% CI (horizontal line). SMD, standardized mean difference; CI, confidence interval; SUCRA, surface under the cumulative ranking curve; RT, resistance training; RC, regular care.

Figure 5

Network diagram illustrating the interconnections among different treatment arms for muscle strength. Each node represents a treatment arm, and the size of the node is proportional to the number of participants assigned to the specific treatment. The thickness of each line is proportional to the number of direct comparisons between arms denoted on the line. RT, resistance training.

Figure 6

Relative efficacy of treatment regimens on muscle strength during an overall follow-up duration. Each point estimate (square) presents the network combined effect (SMD) on the outcome measure relative to RC, with the 95% CI (horizontal line). SMD, standardized mean difference; CI, confidence interval; SUCRA, surface under the cumulative ranking curve; RT, resistance training; RC, regular care.

Figure 7

Network diagram illustrating the interconnections among different treatment arms for physical mobility. Each node represents a treatment arm, and the size of the node is proportional to the number of participants assigned to the specific treatment. The thickness of each line is proportional to the number of direct comparisons between arms denoted on the line. RT, resistance training; SPPB, Short Physical Performance Battery.

Figure 8

Relative efficacy among treatment regimens on changes in physical mobility scores during an overall study time. Each point estimate (square) presents the network combined effect on the specific outcome measure, with the 95% CI (horizontal line). The positive results indicate favorable efficacy of the treatment regimen compared to RC. The blue-colored point represents the highest probability of effects among all treatment regimens. Std, standardized; CI, confidence interval; RT, resistance training; SPPB, Short Physical Performance Battery; RC, regular care.

Figure 9

Participant compliance and side effects of treatment regimens. Data concerning treatment-related (A) withdrawals and (B) adverse events were pooled using inverse variance weighting methods. Each point estimate (square) presents the network combined effect (OR) of the indicated treatment arm relative to RC, with the 95% CI (horizontal line). OR, odds ratio; CI, confidence interval; RT, resistance training.