title: The effect of dietary nitrate supplementation on the oxygen cost of cycling, walking performance and resting blood pressure in individuals with chronic obstructive pulmonary disease: A double blind placebo controlled, randomised control trial.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) results in exercise intolerance. Dietary nitrate supplementation has been shown to lower blood pressure (BP), reduce the oxygen cost of exercise, and enhance exercise tolerance in healthy volunteers. This study assessed the effects of dietary nitrate on the oxygen cost of cycling, walking performance and BP in individuals with mild-moderate COPD.
  
  
  METHODS
  Thirteen patients with mild-moderate COPD were recruited. Participants consumed 70 ml of either nitrate-rich (6.77 mmol nitrate; beetroot juice) or nitrate-depleted beetroot juice (0.002 mmol nitrate; placebo) twice a day for 2.5 days, with the final supplement ~3 hours before testing. BP was measured before completing two bouts of moderate-intensity cycling, where pulmonary gas exchange was measured throughout. The six-minute walk test (6 MWT) was completed 30 minutes subsequent to the second cycling bout.
  
  
  RESULTS
  Plasma nitrate concentration was significantly elevated following beetroot juice vs. placebo (placebo; 48 ± 86 vs. beetroot juice; 215 ± 84 µM, P = 0.002). No significant differences were observed between placebo vs. beetroot juice for oxygen cost of exercise (933 ± 323 vs. 939 ± 302 ml: min(-1); P = 0.88), distance covered in the 6 MWT (456 ± 86 vs. 449 ± 79 m; P = 0.37), systolic BP (123 ± 14 vs. 123 ± 14 mmHg; P = 0.91), or diastolic BP (77 ± 9 vs. 79 ± 9 mmHg; P = 0.27).
  
  
  CONCLUSIONS
  Despite a large rise in plasma nitrate concentration, two days of nitrate supplementation did not reduce the oxygen cost of moderate intensity cycling, increase distance covered in the 6 MWT, or lower BP.
authors.affiliation: College of Life and Environmental Sciences, Sport and Health Sciences, University of Exeter, Devon, UK; NIHR Exeter Clinical Research Facility, Royal Devon and Exeter Hospital, University of Exeter Medical School, Exeter, Devon, UK.
authors.forename: Anthony I
authors.initials: AI
authors.lastname: Shepherd
authors.affiliation: College of Life and Environmental Sciences, Sport and Health Sciences, University of Exeter, Devon, UK.
authors.forename: Daryl P
authors.initials: DP
authors.lastname: Wilkerson
authors.affiliation: Heart and Lung Unit, Torbay Hospital, Torquay, Devon, UK.
authors.forename: Lee
authors.initials: L
authors.lastname: Dobson
authors.affiliation: College of Life and Environmental Sciences, Sport and Health Sciences, University of Exeter, Devon, UK.
authors.forename: James
authors.initials: J
authors.lastname: Kelly
authors.affiliation: NIHR Exeter Clinical Research Facility, Royal Devon and Exeter Hospital, University of Exeter Medical School, Exeter, Devon, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Winyard
authors.affiliation: College of Life and Environmental Sciences, Sport and Health Sciences, University of Exeter, Devon, UK.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
authors.affiliation: NIHR Exeter Clinical Research Facility, Royal Devon and Exeter Hospital, University of Exeter Medical School, Exeter, Devon, UK; Heart and Lung Unit, Torbay Hospital, Torquay, Devon, UK.
authors.forename: Nigel
authors.initials: N
authors.lastname: Benjamin
authors.affiliation: NIHR Exeter Clinical Research Facility, Royal Devon and Exeter Hospital, University of Exeter Medical School, Exeter, Devon, UK.
authors.forename: Angela C
authors.initials: AC
authors.lastname: Shore
authors.affiliation: NIHR Exeter Clinical Research Facility, Royal Devon and Exeter Hospital, University of Exeter Medical School, Exeter, Devon, UK. Electronic address: m.gilchrist@exeter.ac.uk.
authors.forename: Mark
authors.initials: M
authors.lastname: Gilchrist
mesh_terms: D000328:Adult; D000368:Aged; D027461:Beta vulgaris; D001794:Blood Pressure / Q000187:drug effects*; D019587:Dietary Supplements; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009566:Nitrates / Q000097:blood / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000178:diet therapy* / Q000503:physiopathology; D011659:Pulmonary Gas Exchange; D016138:Walking
chemical_list: D009566:Nitrates; D010100:Oxygen
keywords: Blood pressure; COPD; Diet; Exercise; Nitrate; Nitric oxide