Objective To conduct a systematic review and meta-analysis of the evidence on the effects of β-alanine supplementation on exercise capacity and performance.
Design This study was designed in accordance with PRISMA guidelines. A 3-level mixed effects model was employed to model effect sizes and account for dependencies within data.
Data sources 3 databases (PubMed, Google Scholar, Web of Science) were searched using a number of terms (‘β-alanine’ and ‘Beta-alanine’ combined with ‘supplementation’, ‘exercise’, ‘training’, ‘athlete’, ‘performance’ and ‘carnosine’).
Eligibility criteria for selecting studies Inclusion/exclusion criteria limited articles to double-blinded, placebo-controlled studies investigating the effects of β-alanine supplementation on an exercise measure. All healthy participant populations were considered, while supplementation protocols were restricted to chronic ingestion. Cross-over designs were excluded due to the long washout period for skeletal muscle carnosine following supplementation. A single outcome measure was extracted for each exercise protocol and converted to effect sizes for meta-analyses.
Results 40 individual studies employing 65 different exercise protocols and totalling 70 exercise measures in 1461 participants were included in the analyses. A significant overall effect size of 0.18 (95% CI 0.08 to 0.28) was shown. Meta-regression demonstrated that exercise duration significantly (p=0.004) moderated effect sizes. Subgroup analyses also identified the type of exercise as a significant (p=0.013) moderator of effect sizes within an exercise time frame of 0.5–10 min with greater effect sizes for exercise capacity (0.4998 (95% CI 0.246 to 0.753)) versus performance (0.1078 (95% CI −0.201 to 0.416)). There was no moderating effect of training status (p=0.559), intermittent or continuous exercise (p=0.436) or total amount of β-alanine ingested (p=0.438). Co-supplementation with sodium bicarbonate resulted in the largest effect size when compared with placebo (0.43 (95% CI 0.22 to 0.64)).
Summary/conclusions β-alanine had a significant overall effect while subgroup analyses revealed a number of modifying factors. These data allow individuals to make informed decisions as to the likelihood of an ergogenic effect with β-alanine supplementation based on their chosen exercise modality.
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Contributors BS, BG and CS contributed to the conception and design of the study. BS, KES and GGA contributed to the development of the search strategy analysis and to the acquisition of data. BS, PAS, ED and HR performed the data analysis and interpretation of data. BS was the principal writer of the article while all authors contributed to the drafting of the article and revising it critically. All authors approved the final version to be submitted.
Funding BS (150513/2015-1) has been financially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). GGA, ED and BG have been financially supported by Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP grant numbers: 2014/11948-8, 2015/11328-2 and 2013/14746-4).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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