The Role of Protein Intake and its Timing on Body Composition and Muscle Function in Healthy Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

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dc.contributor.authorWirth, Janine-
dc.contributor.authorHillesheim, Elaine-
dc.contributor.authorBrennan, Lorraine- the Authorsen_US
dc.identifier.citationThe Journal of Nutritionen_US
dc.description.abstractBackground Increased protein intake has been suggested to improve gains in muscle mass and strength in adults. Furthermore, the timing of protein intake has been discussed as a margin of opportunity for improved prevention measures.Objective This systematic review investigated the effect of protein supplementation on body composition and muscle function (strength and synthesis) in healthy adults, with an emphasis on the timing of protein intake.Methods Randomized controlled trials were identified using PubMed, Web of Science, CINAHL, and Embase, up to March 2019. For meta-analyses, data on lean body mass (LBM), handgrip strength, and leg press strength were pooled by age group (mean age 18–55 or >55 y) and timing of protein intake. The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations approach.Results Data from 65 studies with 2907 participants (1514 men and 1380 women, 13 unknown sex) were included in the review. Twenty-six, 8, and 24 studies were used for meta-analysis on LBM, handgrip strength, and leg press strength, respectively. The protein supplementation was effective in improving (mean difference; 95% CI) LBM in adults (0.62 kg; 0.36, 0.88) and older adults (0.46 kg; 0.23, 0.70), but not handgrip strength (older adults: 0.26 kg; -0.51, 1.04) and leg press strength (adults: 5.80 kg; -0.33, 11.93; older adults: 1.97 kg; -2.78, 6.72). Sensitivity analyses removing studies without exercise training had no impact on the outcomes. Data regarding muscle synthesis were scarce and inconclusive. Subgroup analyses showed no beneficial effect of a specific timing of protein intake on LBM, handgrip strength, and leg press strength.Conclusion Overall, the results support the positive impact of protein supplementation on LBM of adults and older adults, independently of intake timing. Effects on muscle strength and synthesis are less clear and need further investigation. This systematic review was registered on PROSPERO as CRD42019126742.en_US
dc.description.sponsorshipEnterprise Irelanden_US
dc.description.sponsorshipEuropean Commission Horizon 2020en_US
dc.description.sponsorshipEuropean Research Councilen_US
dc.publisherOxford University Pressen_US
dc.rightsThis is a pre-copyedited, author-produced PDF of an article accepted for publication in The Journal of Nutrition following peer review. The definitive publisher-authenticated version Janine Wirth, Elaine Hillesheim, Lorraine Brennan, The Role of Protein Intake and its Timing on Body Composition and Muscle Function in Healthy Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials, The Journal of Nutrition is available online at:
dc.subjectTiming of intakeen_US
dc.subjectBody compositionen_US
dc.subjectLean body massen_US
dc.subjectMuscle strengthen_US
dc.subjectMuscle synthesisen_US
dc.titleThe Role of Protein Intake and its Timing on Body Composition and Muscle Function in Healthy Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trialsen_US
dc.title.alternativeEffect and timing of protein intakeen_US
dc.typeJournal Articleen_US
dc.statusPeer revieweden_US
dc.description.othersponsorshipBrazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES)en_US
item.fulltextWith Fulltext-
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Institute of Food and Health Research Collection
Agriculture and Food Science Research Collection
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