Dietary nitrate supplementation improves exercise performance and decreases blood pressure in COPD patients

Abstract

Dietary nitrate (NO3(-)) supplementation via beetroot juice has been shown to increase the exercise capacity of younger and older adults. The purpose of this study was to investigate the effects of acute NO3(-) ingestion on the submaximal constant work rate exercise capacity of COPD patients. Fifteen patients were assigned in a randomized, single-blind, crossover design to receive one of two treatments (beetroot juice then placebo or placebo then beetroot juice). Submaximal constant work rate exercise time at 75% of the patient's maximal work capacity was the primary outcome. Secondary outcomes included plasma NO3(-) and nitrite (NO2(-)) levels, blood pressure, heart rate, oxygen consumption (VO2), dynamic hyperinflation, dyspnea and leg discomfort. Relative to placebo, beetroot ingestion increased plasma NO3(-) by 938% and NO2(-) by 379%. Median (+interquartile range) exercise time was significantly longer (p = 0.031) following the ingestion of beetroot versus placebo (375.0 + 257.0 vs. 346.2 + 148.0 s, respectively). Compared with placebo, beetroot ingestion significantly reduced iso-time (p = 0.001) and end exercise (p = 0.008) diastolic blood pressures by 6.4 and 5.6 mmHg, respectively. Resting systolic blood pressure was significantly reduced (p = 0.019) by 8.2 mmHg for the beetroot versus the placebo trial. No other variables were significantly different between the beetroot and placebo trials. These results indicate that acute dietary NO3(-) supplementation can elevate plasma NO3(-) and NO2(-) concentrations, improve exercise performance, and reduce blood pressure in COPD patients.

Keywords: Blood pressure; Chronic obstructive pulmonary disease; Exercise; Nitrate; Nitric oxide; Nitrite.

Copyright © 2014 Elsevier Inc. All rights reserved.

Figures

Figure 1

Illustrates the schematic of trial visits

Figure 2

Illustrates plasma nitrate concentrations expressed as uM of plasma. Both individual and mean ± SEM concentrations are shown for the beetroot juice (BRJ) and placebo trials.

Figure 3

Illustrates plasma nitrite concentrations expressed as nM of plasma for both the beetroot juice and placebo trials. Boxes represent the interquartile ranges with the line within each representing the median value. The error bars project to the 10th and 90th percentiles with the circles at each end representing the smallest and largest values..

Figure 4

Illustrates submaximal constant work rate exercise time in seconds for both the beetroot juice and placebo trials. Boxes represent the interquartile ranges with the line within each representing the median value. The error bars project to the 10th and 90th percentiles with the circles at each end representing the smallest and largest values.