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01.12.2015 | Research article | Ausgabe 1/2015 Open Access

BMC Pulmonary Medicine 1/2015

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

Zeitschrift:
BMC Pulmonary Medicine > Ausgabe 1/2015
Autoren:
Paul Leong, Jane E Basham, Theresa Yong, Adrian Chazan, Paul Finlay, Sara Barnes, Phillip G Bardin, Donald Campbell
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​s12890-015-0057-4) contains supplementary material, which is available to authorized users.

Competing interests

The authors declare that they have no competing interests, financial or non-financial.

Author contributions

DC, PB, PF and AC conceived the study. PL, JB, SB and TY recruited subjects, performed all tests and collected primary data. PL and DC performed statistical analysis. PL and DC drafted the initial manuscript. All authors read and approved the final manuscript.

Abstract

Background

Dietary 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.

Methods

We 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.

Results

35 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).

Conclusions

Our study does not support a role for routine dietary nitrate supplementation for enhancement of exercise endurance in COPD.

Trial registration

Australia and New Zealand Clinical Trial Register: ACTRN12611001088​932
Zusatzmaterial
Additional file 1: Table S1. Safety phase data for diastolic blood pressure (DBP) on standing (mmHg) (n=23 unless otherwise stated).
12890_2015_57_MOESM1_ESM.docx
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