title: Acute Dietary Nitrate Supplementation and Exercise Performance in COPD: A Double-Blind, Placebo-Controlled, Randomised Controlled Pilot Study.
abstract: BACKGROUND
  Dietary nitrate supplementation can enhance exercise performance in healthy people, but it is not clear if it is beneficial in COPD. We investigated the hypotheses that acute nitrate dosing would improve exercise performance and reduce the oxygen cost of submaximal exercise in people with COPD.
  
  
  METHODS
  We performed a double-blind, placebo-controlled, cross-over single dose study. Subjects were randomised to consume either nitrate-rich beetroot juice (containing 12.9 mmoles nitrate) or placebo (nitrate-depleted beetroot juice) 3 hours prior to endurance cycle ergometry, performed at 70% of maximal workload assessed by a prior incremental exercise test. After a minimum washout period of 7 days the protocol was repeated with the crossover beverage.
  
  
  RESULTS
  21 subjects successfully completed the study (age 68 ± 7 years; BMI 25.2 ± 5.5 kg/m2; FEV1 percentage predicted 50.1 ± 21.6%; peak VO2 18.0 ± 5.9 ml/min/kg). Resting diastolic blood pressure fell significantly with nitrate supplementation compared to placebo (-7 ± 8 mmHg nitrate vs. -1 ± 8 mmHg placebo; p = 0.008). Median endurance time did not differ significantly; nitrate 5.65 (3.90-10.40) minutes vs. placebo 6.40 (4.01-9.67) minutes (p = 0.50). However, isotime oxygen consumption (VO2) was lower following nitrate supplementation (16.6 ± 6.0 ml/min/kg nitrate vs. 17.2 ± 6.0 ml/min/kg placebo; p = 0.043), and consequently nitrate supplementation caused a significant lowering of the amplitude of the VO2-percentage isotime curve.
  
  
  CONCLUSIONS
  Acute administration of oral nitrate did not enhance endurance exercise performance; however the observation that beetroot juice caused reduced oxygen consumption at isotime suggests that further investigation of this treatment approach is warranted, perhaps targeting a more hypoxic phenotype.
  
  
  BACKGROUND
  ISRCTN Registry ISRCTN66099139.
authors.affiliation: NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Trust and Imperial College, London, United Kingdom.
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Curtis
authors.affiliation: Centre of Human & Aerospace Physiological Sciences, King's College London, London, United Kingdom.
authors.forename: Katie A
authors.initials: KA
authors.lastname: O'Brien
authors.affiliation: NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Trust and Imperial College, London, United Kingdom.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Tanner
authors.affiliation: NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Trust and Imperial College, London, United Kingdom.
authors.forename: Juliet I
authors.initials: JI
authors.lastname: Polkey
authors.affiliation: Faculty of Medicine, Clinical and Experimental Sciences, University of Southampton, and Southampton NIHR Respiratory Biomedical Research Unit, Southampton General Hospital, Southampton, United Kingdom.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Minnion
authors.affiliation: Faculty of Medicine, Clinical and Experimental Sciences, University of Southampton, and Southampton NIHR Respiratory Biomedical Research Unit, Southampton General Hospital, Southampton, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Feelisch
authors.affiliation: NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Trust and Imperial College, London, United Kingdom.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.affiliation: Centre of Human & Aerospace Physiological Sciences, King's College London, London, United Kingdom.
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Edwards
authors.affiliation: NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Trust and Imperial College, London, United Kingdom.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005081:Exercise Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009566:Nitrates / Q000008:administration & dosage*; D010101:Oxygen Consumption; D010865:Pilot Projects; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000628:therapy*
chemical_list: D009566:Nitrates