Synergistic Effect of Increased Total Protein Intake and Strength Training on Muscle Strength: A Dose-Response Meta-analysis of Randomized Controlled Trials

Abstract

Background Protein supplementation augments muscle strength gain during resistance training. Although some studies focus on the dose-response relationship of total protein intake to muscle mass or strength, the detailed dose-response relationship between total protein intake and muscle strength increase is yet to be clarified, especially in the absence of resistance training. Objective We aimed to assess the detailed dose-response relationship between protein supplementation and muscle strength, with and without resistance training. Design Systematic review with meta-analysis. Data Sources PubMed and Ichushi-Web (last accessed on March 23, 2022). Eligibility Criteria Randomized controlled trials investigating the effects of protein intake on muscle strength. Synthesis Methods A random-effects model and a spline model. Results A total of 82 articles were obtained for meta-analyses, and data from 69 articles were used to create spline curves. Muscle strength increase was significantly augmented only with resistance training (MD 2.01%, 95% CI 1.09–2.93) and was not augmented if resistance training was absent (MD 0.13%, 95% CI − 1.53 to 1.79). In the dose-response analysis using a spline model, muscle strength increase with resistance training showed a dose-dependent positive association with total protein intake, which is 0.72% (95% CI 0.40–1.04%) increase in muscle strength per 0.1 g/kg body weight [BW]/d increase in total protein intake up to 1.5 g/kg BW/d, but no further gains were observed thereafter. Conclusion Concurrent use of resistance training is essential for protein supplementation to improve muscle strength. This study indicates that 1.5 g/kg BW/d may be the most appropriate amount of total protein intake for maintaining and augmenting muscle strength along with resistance training.

Are higher protein intake and distribution of protein intake related to higher appendicular muscle mass among an older Japanese population?: A cross‐sectional analysis of the National Health and Nutrition Survey 2017

“…A recent review 28 found that in participants >65 years old undertaking resistance training, the addition of 1.2–1.59 g/kg protein intake resulted in higher increases in lean mass than did lower protein intake. A review of resistance training interventions 29 showed that increases in protein intake up to 1.5 g/kg resulted in an increase in muscle power. Among intervention trials involving >1.3 g/kg protein intake, lean mass continued to rise in studies with resistance training but declined without resistance training, even with increased protein intake 30 .…”

Whey Protein Supplementation with or without Vitamin D on Sarcopenia-Related Measures: A Systematic Review and Meta-Analysis

“…[ 7 ]; an I 2 of 50%–56% for strength in Tagawa et al. [ 75 ]; and an I 2 of 90% or more for strength and physical function in Chang et al. [ 15 ].…”

Protein Intake in NCAA Division 1 Soccer Players: Assessment of Daily Amounts, Distribution Patterns, and Leucine Levels as a Quality Indicator

“…It has been suggested that the overall amount of dietary protein consumed daily appears to be the principal nutritional determinant of skeletal muscle anabolism. Though it was originally proposed that the Recommended Dietary Allowance (RDA) of 0.8 g protein/kg BW/day is sufficient for athletes, recent meta-analyses suggest that optimum adaptation occurs with intakes of ~1.6 g protein/kg BW/day when paired with appropriate exercise training, though intakes upwards of ~2.2 g protein/kg BW/day may be warranted in certain cases [ 11 , 12 , 37 , 38 , 39 ]. Consistent with the most recent evidence, the UEFA expert panel advises intakes of 1.6–2.2 g protein/kg BW/day for soccer players [ 3 ].…”

“…The consensus report authored by FIFA/FIFA-Medical Assessment Research Center (F-MARC) in 2006 specifies that a maximum of 1.2–1.6 protein/kg BW/day may be needed by soccer athletes, though stating that the evidence of this is “not clear or universal” [ 10 ]. By comparison, more recently issued soccer-specific sports nutrition guidance by an expert group commissioned by the Union of European Football Associations (UEFA) recommends protein intakes in the range of 1.6–2.2 g/kg BW/day [ 3 ], in concert with accumulating evidence that these intakes maximally augment the skeletal muscle adaptive response to exercise training [ 11 , 12 ].…”