Objective To determine the effects of multi-ingredient protein (MIP) supplements on resistance exercise training (RT)-induced gains in muscle mass and strength compared with protein-only (PRO) or placebo supplementation.
Data sources Systematic search of MEDLINE, Embase, CINAHL and SPORTDiscus.
Eligibility criteria Randomised controlled trials with interventions including RT ≥6 weeks in duration and a MIP supplement.
Design Random effects meta-analyses were conducted to determine the effect of supplementation on fat-free mass (FFM), fat mass, one-repetition maximum (1RM) upper body and 1RM lower body muscular strength. Subgroup analyses compared the efficacy of MIP supplementation relative to training status and chronological age.
Results The most common MIP supplements included protein with creatine (n=17) or vitamin D (n=10). Data from 35 trials with 1387 participants showed significant (p<0.05) increases in FFM (0.80 kg (95% CI 0.44 to 1.15)), 1RM lower body (4.22 kg (95% CI 0.79 to 7.64)) and 1RM upper body (2.56 kg (95% CI 0.79 to 4.33)) where a supplement was compared with all non-MIP supplemented conditions (means (95% CI)). Subgroup analyses indicated a greater effect of MIP supplements compared with all non-MIP supplements on FFM in untrained (0.95 kg (95% CI 0.51 to 1.39), p<0.0001) and older participants (0.77 kg (95% CI 0.11 to 1.43), p=0.02); taking MIP supplements was also associated with gains in 1RM upper body (1.56 kg (95% CI 0.80 to 2.33), p=0.01) in older adults.
Summary/conclusions When MIP supplements were combined with resistance exercise training, there were greater gains in FFM and strength in healthy adults than in counterparts who were supplemented with non-MIP. MIP supplements were not superior when directly compared with PRO supplements. The magnitude of effect of MIP supplements was greater (in absolute values) in untrained and elderly individuals undertaking RT than it was in trained individuals and in younger people.
Trial registration number CRD42017081970.
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Contributors All authors contributed to the conception and design of the study. KRO and RWM contributed to the development and implementation of the search strategy. KRO and TMD completed the acquisition of data. KRO and TMD conducted the data analysis. All authors contributed with the interpretation. KRO and TMD were the principal authors of the manuscript. All authors contributed to the drafting and revision of the final manuscript. All authors approved the final version of the article.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests SMP has received grant support, travel expenses and honoraria for presentations from the US National Dairy Council. This agency has supported trials reviewed in this analysis.
Provenance and peer review Not commissioned; externally peer reviewed.
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