Abstract
Abstract Objectives Poor sleep is increasingly seen as an issue of public health concern. The evidence to support the relationship between protein intake and sleep hygiene is limited and inconclusive. Therefore, the aim of this systematic review and meta-analysis was to examine the association between protein intake and subjective and objective sleep parameters in adults. Methods On June 22nd, 2020, five electronic databases were searched to identify relevant randomised controlled trials (Pubmed, Cochrane, Embase, Web of Science and CINAHL Plus). Risk of bias of included studies was assessed by outcomes using the Cochrane risk-of-bias 2.0 tool. Meta-analyses were performed for the outcomes sleep latency (SL), sleep efficiency (SE), and sleep quality (SQ). The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Results A total of 12 intervention studies from 10 articles were included. Meta-analyses showed no significant association between sleep outcomes (SQ = eight studies, SL = seven studies, SE = six studies) and increased protein intake, with very low certainty of evidence. However, results from sensitivity analyses excluding high-risk studies from parallel design trials suggest a small effect on SQ in favour of high protein intake (mean difference: −6.95; 95% CI: −12.52, −1.41; on a scale ranging from 0 to 100). Conclusions Our systematic review and meta-analysis indicate that there is no clear relationship between protein intake and sleep. However, the strength of the evidence is rather low. Further RCTs that focus on this specific research question are warranted, considering a more appropriate study design. This systematic review was registered with the International Prospective Register of Systematic Reviews, PROSPERO (CRD42020196021). Funding Sources This work was supported by: Marie Skłodowska-Curie Career Development Fellowship in the National Technology Centre Programme funded through a cofund with the European Union's Horizon 2020 and Enterprise Ireland; European Research Council (ERC); Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) as part of the Full PhD Abroad Program. Funding agencies had no role in the design, analysis, or writing of this article.
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