title: Effect of dietary nitrate supplementation on metabolic rate during rest and exercise in human: A systematic review and a meta-analysis.
abstract: BACKGROUND
  Recent randomized controlled trials have suggested that dietary nitrate (NO3(-)), found in beetroot and other vegetables, and inorganic NO3(-) salts decrease metabolic rate under resting and exercise conditions.
  
  
  OBJECTIVE
  Our aim was therefore to determine from a systematic review and meta-analysis whether dietary NO3(-) supplementation significantly reduces metabolic rate, expressed as oxygen uptake (VO2), under resting and exercise conditions in healthy humans and those with cardiorespiratory diseases.
  
  
  METHODS
  A systematic article search was performed on electronic databases (PubMed, Scopus and Web of Science) from February to March 2015. The inclusion criteria included 1) randomized controlled trials; 2) studies reporting the effect of NO3(-) on VO2 under resting and/or exercise conditions; 3) comparison between dietary NO3(-) supplementation and placebo. Random-effects models were used to calculate the pooled effect size.
  
  
  RESULTS
  Twenty nine randomized placebo-controlled trials were included in the systematic review, and 26 of which were included in the meta-analysis. Dietary NO3(-) supplementation significantly decreases VO2 during submaximal intensity exercise [-0.26 (95% IC: -0.38, -0.15), p < 0.01], but not in the sub-analysis of subjects with chronic diseases [-0.09 (95% IC: -0.50, 0.32), p = 0.67]. When data were separately analyzed by submaximal intensity domains, NO3(-) supplementation reduces VO2 during moderate [-0.29 (95% IC: -0.48,-0.10), p < 0.01] and heavy [-0.33 (95% IC: -0.54,-0.12), p < 0.01] intensity exercise. When the studies with the largest effects were excluded from the meta-analysis, there is a trend for a VO2 decrease under resting condition in dietary NO3(-) supplementation [-0.28 (95% IC: -0.62, 0.05), p = 0.10].
  
  
  CONCLUSIONS
  Dietary NO3(-) supplementation decreases VO2 during exercise performed in the moderate and heavy intensity domains in healthy subjects. The present meta-analysis did not show any significant effect of dietary NO3(-) supplementation on metabolic rate in subjects with chronic diseases, despite enhanced exercise tolerance.
authors.affiliation: Université Droit et Santé Lille 2, URePSSS, EA7369, Equipe «Activité Physique, Muscle, Santé», Faculté des Sciences du Sport et de l'Education Physique, Ronchin, France.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Pawlak-Chaouch
authors.affiliation: Université Droit et Santé Lille 2, URePSSS, EA7369, Equipe «Activité Physique, Muscle, Santé», Faculté des Sciences du Sport et de l'Education Physique, Ronchin, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Boissière
authors.affiliation: Université Droit et Santé Lille 2, URePSSS, EA7369, Equipe «Activité Physique, Muscle, Santé», Faculté des Sciences du Sport et de l'Education Physique, Ronchin, France.
authors.forename: François X
authors.initials: FX
authors.lastname: Gamelin
authors.affiliation: Pôle Hainuyer, Laboratoire de l'Effort et du Mouvement, Haute Ecole Provinciale de Hainaut-Condorcet, Tournai, Belgium.
authors.forename: Grégory
authors.initials: G
authors.lastname: Cuvelier
authors.affiliation: Université Droit et Santé Lille 2, URePSSS, EA7369, Equipe «Activité Physique, Muscle, Santé», Faculté des Sciences du Sport et de l'Education Physique, Ronchin, France.
authors.forename: Serge
authors.initials: S
authors.lastname: Berthoin
authors.affiliation: Université Droit et Santé Lille 2, URePSSS, EA7369, Equipe «Activité Physique, Muscle, Santé», Faculté des Sciences du Sport et de l'Education Physique, Ronchin, France. Electronic address: julien.aucouturier@univ-lille2.fr.
authors.forename: Julien
authors.initials: J
authors.lastname: Aucouturier
mesh_terms: D019587:Dietary Supplements; D004734:Energy Metabolism / Q000187:drug effects*; D015444:Exercise; D006801:Humans; D009566:Nitrates / Q000008:administration & dosage* / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism*; D016032:Randomized Controlled Trials as Topic; D012146:Rest
chemical_list: D009566:Nitrates; D010100:Oxygen
keywords: Chronic diseases; Dietary nitrate; Exercise; Metabolic rate; Rest