Protein Source and Quality for Skeletal Muscle Anabolism in Young and Older Adults: A Systematic Review and Meta-Analysis.

Paul T Morgan,Leigh Breen,Ryan N Marshall,Sophie J Edwards,Sophie L Allen,Dane O Harris,Jonathan I Quinlan

doi:10.1093/jn/nxab055

Abstract

ABSTRACTBackgroundThere is much debate regarding the source/quality of dietary proteins in supporting indices of skeletal muscle anabolism.ObjectiveWe performed a systematic review and meta-analysis to determine the effect of protein source/quality on acute muscle protein synthesis (MPS) and changes in lean body mass (LBM) and strength, when combined with resistance exercise (RE).MethodsA systematic search of the literature was conducted to identify studies that compared the effects of ≥2 dose-matched, predominantly isolated protein sources of varying “quality.” Three separate models were employed as follows: 1) protein feeding alone on MPS, 2) protein feeding combined with a bout of RE on MPS, and 3) protein feeding combined with longer-term resistance exercise training (RET) on LBM and strength. Further subgroup analyses were performed to compare the effects of protein source/quality between young and older adults. A total of 27 studies in young (18–35 y) and older (≥60 y) adults were included.ResultsAnalysis revealed an effect favoring higher-quality protein for postprandial MPS at rest [mean difference (MD): 0.014%/h; 95% CI: 0.006, 0.021; P < 0.001] and following RE (MD: 0.022%/h; 95% CI: 0.014, 0.030; P < 0.00001) in young (model 1: 0.016%/h; 95% CI: −0.004, 0.036; P = 0.12; model 2: 0.030%/h; 95% CI: 0.015, 0.045; P < 0.0001) and older (model 1: 0.012%/h; 95% CI: 0.006, 0.018; P < 0.001; model 2: 0.014%/h; 95% CI: 0.007, 0.021; P < 0.001) adults. However, although higher protein quality was associated with superior strength gains with RET [standardized mean difference (SMD): 0.24 kg; 95% CI: 0.02, 0.45; P = 0.03)], no effect was observed on changes to LBM (SMD: 0.05 kg; 95% CI: −0.16, 0.25; P = 0.65).ConclusionsThe current review suggests that protein quality may provide a small but significant impact on indices of muscle protein anabolism in young and older adults. However, further research is warranted to elucidate the importance of protein source/quality on musculoskeletal aging, particularly in situations of low protein intake.

Highlights

The regulation of skeletal muscle is a complex process that hinges on the dynamic balance between muscle protein synthesis (MPS) and muscle protein breakdown [1,2,3,4]
A systematic search of the literature was conducted to identify studies that compared the effects of ≥2 dosematched, predominantly isolated protein sources of varying “quality.” Three separate models were employed as follows: 1) protein feeding alone on MPS, 2) protein feeding combined with a bout of RE on MPS, and 3) protein feeding combined with longer-term resistance exercise training (RET) on lean body mass (LBM) and strength
Protein dose for model 3 within the protein supplement ranged from 10.0 to 48.0 g, which equated to 5.2–25.1 g and 1.7–20.3 g of essential amino acid (EAA) for HIGH and CON, respectively

Summary

Introduction

The regulation of skeletal muscle is a complex process that hinges on the dynamic balance between muscle protein synthesis (MPS) and muscle protein breakdown [1,2,3,4]. Objective: We performed a systematic review and meta-analysis to determine the effect of protein source/quality on acute muscle protein synthesis (MPS) and changes in lean body mass (LBM) and strength, when combined with resistance exercise (RE). Results: Analysis revealed an effect favoring higher-quality protein for postprandial MPS at rest [mean difference (MD): 0.014%/h; 95% CI: 0.006, 0.021; P < 0.001] and following RE (MD: 0.022%/h; 95% CI: 0.014, 0.030; P < 0.00001) in young (model 1: 0.016%/h; 95% CI: −0.004, 0.036; P = 0.12; model 2: 0.030%/h; 95% CI: 0.015, 0.045; P < 0.0001) and older (model 1: 0.012%/h; 95% CI: 0.006, 0.018; P < 0.001; model 2: 0.014%/h; 95% CI: 0.007, 0.021; P < 0.001) adults. Conclusions: The current review suggests that protein quality may provide a small but significant impact on indices of muscle protein anabolism in young and older adults.

Objectives

Methods

Results

Discussion

Conclusion