title: Effects of inorganic nitrate and beetroot supplementation on endothelial function: a systematic review and meta-analysis.
abstract: BACKGROUND
  Diets rich in inorganic nitrate are associated with lower blood pressure, an effect that may be mediated by an improvement of endothelial function (EF). Therefore, a systematic review and meta-analysis of randomised controlled trials (RCTs) were conducted to examine the effects of inorganic nitrate and beetroot supplementation on measures of EF.
  
  
  METHODS
  MEDLINE, EMBASE and Scopus databases were searched from inception until November 2014. Specific inclusion criteria were as follows: (1) RCTs; (2) trials comparing inorganic nitrate or beetroot supplementation with placebo control groups; and (3) trials reporting effects of these interventions on outcomes of vascular function. Random-effect models were used to assess the pooled effect sizes showed as standardised mean differences (SMD).
  
  
  RESULTS
  Nine crossover trials and three parallel trials met our inclusion criteria. The trials were conducted between 2008 and 2014 and included a total of 246 participants with 10-64 participants per study. The duration of each intervention ranged from 1.5 h to 28 days. Inorganic nitrate and beetroot consumption was associated with an improvement in vascular function (SMD 0.36; 95 % CI 0.16, 0.56; P < 0.001). The effect on EF was significantly associated with the dose of inorganic nitrate (β = 0.04, SE = 0.01, P < 0.001), age (β = -0.01, SE = 0.004, P = 0.02), baseline BMI (β = -0.04, SE = 0.02, P = 0.05) and systolic BP (β = -0.01, SE = 0.005, P = 0.02).
  
  
  CONCLUSIONS
  Inorganic nitrate and beetroot supplementation was associated with beneficial effects on EF. These effects appear to be reduced in older subjects and in subjects with greater cardiometabolic risk.
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK. jose.lara@newcastle.ac.uk.
authors.forename: Jose
authors.initials: J
authors.lastname: Lara
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.|College of Medicine, University of Al-Mustansiriyah, Baghdad, Iraq.
authors.forename: Ammar W
authors.initials: AW
authors.lastname: Ashor
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.
authors.forename: C
authors.initials: C
authors.lastname: Oggioni
authors.affiliation: William Harvey Research Institute, Barts and The London Medical School, Queen Mary University of London, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Ahluwalia
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.
authors.forename: John C
authors.initials: JC
authors.lastname: Mathers
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.
authors.forename: Mario
authors.initials: M
authors.lastname: Siervo
mesh_terms: D027461:Beta vulgaris / Q000737:chemistry*; D001794:Blood Pressure / Q000187:drug effects; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000517:prevention & control; D019587:Dietary Supplements; D004727:Endothelium / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D024821:Metabolic Syndrome / Q000517:prevention & control; D009566:Nitrates / Q000008:administration & dosage*; D018517:Plant Roots / Q000737:chemistry*; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D009566:Nitrates
keywords: Beetroot; Cardiovascular risk; Endothelial function; Flow-mediated dilation; Inorganic nitrate; Meta-analysis