title: β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To conduct a systematic review and meta-analysis of the evidence on the effects of β-alanine supplementation on exercise capacity and performance.
  
  
  METHODS
  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.
  
  
  METHODS
  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').
  
  
  METHODS
  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)).
  
  
  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.
authors: Applied Physiology and Nutrition Research Group, University of São Paulo, São Paulo, Brazil.
authors: Bryan
authors: B
authors: Saunders
authors: Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, Nottingham Trent University, Nottingham, UK.
authors: Kirsty
authors: K
authors: Elliott-Sale
authors: Applied Physiology and Nutrition Research Group, University of São Paulo, São Paulo, Brazil.
authors: Guilherme G
authors: GG
authors: Artioli
authors: School of Health Sciences, Robert Gordon University, Aberdeen, UK.
authors: Paul A
authors: PA
authors: Swinton
authors: Applied Physiology and Nutrition Research Group, University of São Paulo, São Paulo, Brazil.
authors: Eimear
authors: E
authors: Dolan
authors: Applied Physiology and Nutrition Research Group, University of São Paulo, São Paulo, Brazil.
authors: Hamilton
authors: H
authors: Roschel
authors: Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, Nottingham Trent University, Nottingham, UK.
authors: Craig
authors: C
authors: Sale
authors: Applied Physiology and Nutrition Research Group, University of São Paulo, São Paulo, Brazil.
authors: Bruno
authors: B
authors: Gualano
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D002336:Carnosine / Q000737:chemistry; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology*; D016032:Randomized Controlled Trials as Topic; D015091:beta-Alanine / Q000494:pharmacology*
chemical_list: D015091:beta-Alanine; D002336:Carnosine
keywords: Amino acids; Exercise; Meta-analysis; Supplements