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.
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.


BACKGROUND
Australia and New Zealand Clinical Trial Register: ACTRN12611001088932.
Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia. paul.leong@monashhealth.org.
Paul
P
Leong
Department of General Medicine, Monash Medical Centre, 246 Clayton Road, Clayton, VIC, 3168, Australia. janebasham@hotmail.com.
Jane E
JE
Basham
Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia. theresa.yong@monashhealth.org.
Theresa
T
Yong
Department of General Medicine, Monash Medical Centre, 246 Clayton Road, Clayton, VIC, 3168, Australia. adrianchazan@gmail.com.
Adrian
A
Chazan
Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia. paul.finlay@monashhealth.org.|Monash University, Clayton, VIC, Australia. paul.finlay@monashhealth.org.
Paul
P
Finlay
Department of General Medicine, Monash Medical Centre, 246 Clayton Road, Clayton, VIC, 3168, Australia. sara.barnes@monashhealth.org.|Monash University, Clayton, VIC, Australia. sara.barnes@monashhealth.org.
Sara
S
Barnes
Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia. philip.bardin@monash.edu.|Monash University, Clayton, VIC, Australia. philip.bardin@monash.edu.
Phillip G
PG
Bardin
Department of General Medicine, Monash Medical Centre, 246 Clayton Road, Clayton, VIC, 3168, Australia. donald.campbell@monash.edu.|Monash University, Clayton, VIC, Australia. donald.campbell@monash.edu.
Donald
D
Campbell
D000368:Aged; D027461:Beta vulgaris; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D000067030:Fruit and Vegetable Juices; D006801:Humans; D008297:Male; D008875:Middle Aged; D009566:Nitrates; D010101:Oxygen Consumption; D029424:Pulmonary Disease, Chronic Obstructive / Q000178:diet therapy*; D012720:Severity of Illness Index
D009566:Nitrates