A double blind randomized placebo control crossover trial on the effect of dietary nitrate supplementation on exercise tolerance in stable moderate chronic obstructive pulmonary disease

Abstract

BackgroundDietary nitrate supplementation has been shown to decrease the oxygen cost of exercise and prolong exercise tolerance, as measured by sub-maximal exercise endurance distance and time at 85% V̇O2max, in both elite athletes and normal healthy subjects. Patients with chronic obstructive pulmonary disease (COPD) have reduced quality of life and ability to perform activities of daily living attributable to diminished exercise tolerance, and dietary nitrate may be able to ameliorate this.MethodsWe performed a double-blind, computer-randomized placebo control crossover trial at a tertiary Australian hospital to investigate whether dietary nitrate supplementation as beetroot juice (BR) would augment submaximal exercise endurance in individuals with spirometrically confirmed stable moderate COPD. Volunteers underwent an incremental shuttle walk test to determine V̇O2max followed by a test dose of BR to establish safety in the study population. Participants performed an endurance shuttle walk test (ESWT) at 85% V̇O2max after randomization to either a 3 day wash-in of BR (4.8 mmol twice a day) or placebo (nitrate deplete BR), with a final dose on the morning of testing. They then crossed over after 4 day washout. Repeated measures two sided paired t-tests were employed.Results35 participants were recruited with 19 completing the trial. In the initial safety phase, we measured systolic blood pressure over four hours post first dose of BR, and found a mean 10 mmHg decrement maximal at 1 hour. One individual developed symptomatic postural hypotension and was excluded. The primary outcomes of ESWT distance and time to fatigue improved by 11% and 6% respectively; however these differences did not achieve statistical significance (p = 0.494 and 0.693 respectively).ConclusionsOur study does not support a role for routine dietary nitrate supplementation for enhancement of exercise endurance in COPD.Trial registrationAustralia and New Zealand Clinical Trial Register: ACTRN12611001088932Electronic supplementary materialThe online version of this article (doi:10.1186/s12890-015-0057-4) contains supplementary material, which is available to authorized users.

Lifestyle Interventions with a Focus on Nutritional Strategies to Increase Cardiorespiratory Fitness in Chronic Obstructive Pulmonary Disease, Heart Failure, Obesity, Sarcopenia, and Frailty

“…Conversely, in a different study, after a 6-day trial of beetroot juice consumption, distance on the 6MWT did not improve [40]. Similar results were observed in another acute dietary nitrate supplementation intervention that described similar ESWT distance and time to fatigue between active and placebo in the same population [64]. Notably, longer supplementation with beetroot juice (8 days) showed similar results with no improvements in peak VO 2 [41].…”

“…?? Dietary Nitrates [39][40][41]63,64] ↔ ↔ ↑ Nutrition Support Supplements [45][46][47]49,50] ?? ↔ ↔…”

It is rocket science – why dietary nitrate is hard to ‘beet’! Part II: further mechanisms and therapeutic potential of the nitrate‐nitrite‐NO pathway

“…Leong et al . found no effect of 3 days of beetroot juice (4.8 mmol twice a day) on the endurance shuttle walk test (ESWT) distance and time to fatigue at 85% VO 2,max in 19 patients with COPD . Whilst Curtis et al .…”

“…Using the 6MWT, Shepherd et al did not find any effect of beetroot juice on the oxygen cost of exercise or distance covered in 13 patients with COPD [28]. Leong et al found no effect of 3 days of beetroot juice (4.8 mmol twice a day) on the endurance shuttle walk test (ESWT) distance and time to fatigue at 85% VO 2,max in 19 patients with COPD [29]. Whilst Curtis et al did not find any effect on endurance time at 70% of maximal workload of beetroot juice (12.9 mmol nitrate) ingested 3 hours beforehand, isotime oxygen consumption (VO 2 ) was 3-4% lower following nitrate supplementation [30].…”

A critical examination of the ergogenic/therapeutic effects of supplementation to increase nitric oxide bioavailability

“…One study found no differences in blood pressures or six-minute walk distance whereas the other study showed an increase in median sub-maximal constant work rate exercise time of 28.8 seconds and lower diastolic blood pressures during exercise. Two other recent published studies in COPD have similarly conflicting results [11,12].…”