Dietary beetroot juice – effects on physical performance in COPD patients: a randomized controlled crossover trial
Authors Friis AL, Steenholt CB, Løkke A, Hansen M
Received 28 February 2017
Accepted for publication 8 May 2017
Published 15 June 2017 Volume 2017:12 Pages 1765—1773
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Charles Downs
Peer reviewer comments 2
Editor who approved publication: Dr Richard Russell
Anne Louise Friis,1,* Carina Bjørnskov Steenholt,1,* Anders Løkke,2 Mette Hansen1
1Section for Sport Science, Department of Public Health, Aarhus University, Denmark; 2Department of Clinical Medicine, Aarhus University, Denmark
*These authors contributed equally to this work
Background and objective: Dietary beetroot juice (BR) supplementation has been shown to reduce the oxygen (O2) consumption of standardized exercise and reduce resting blood pressure (BP) in healthy individuals. However, the physiological response of BR in chronic obstructive pulmonary disease (COPD) remains controversial. The objective was to test exercise performance in COPD, supplementing with higher doses of BR for a longer duration compared to previous trials in this patient group.
Methods: Fifteen COPD patients consumed concentrated BR (2×70 mL twice daily, each containing 300 mg nitrate) or placebo (PL) (2×70 mL twice daily, nitrate-negligible) in a randomized order for 6 consecutive days. On day 7, participants consumed either BR or PL 150 min before testing. BP was measured before completing 6-minute walk test (6MWT) and two trials of submaximal cycling. The protocol was repeated after a minimum washout of 7 days.
Results: Plasma nitrite concentration was higher in the BR condition compared to PL (P<0.01). There was no difference between the BR and PL conditions regarding the covered distance during the 6MWT (mean ± standard error of the mean: 515±35 m (BR) vs 520±38 m (PL), P=0.46), O2 consumption of submaximal exercise (trial 1 P=0.31 vs trial 2 P=0.20), physical activity level (P>0.05), or systolic BP (P=0.80). However, diastolic BP (DBP) was reduced after BR ingestion compared to baseline (mean difference: 4.6, 95% CI: 0.1–9.1, P<0.05).
Conclusion: Seven days of BR ingestion increased plasma nitrite concentrations and lowered DBP in COPD patients. However, BR did not increase functional walking capacity, O2 consumption during submaximal cycling, or physical activity level during the intervention period.
Keywords: nitric oxide, chronic obstructive pulmonary disease, exercise, nitrate, beetroot juice, blood pressure, nitrite
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