Acute Dietary Nitrate Supplementation and Exercise Performance in COPD: A
Double-Blind, Placebo-Controlled, Randomised Controlled Pilot Study
#MMPMID26698120
Curtis KJ
; O'Brien KA
; Tanner RJ
; Polkey JI
; Minnion M
; Feelisch M
; Polkey MI
; Edwards LM
; Hopkinson NS
PLoS One
2015[]; 10
(12
): e0144504
PMID26698120
show ga
BACKGROUND: Dietary nitrate supplementation can enhance exercise performance in
healthy people, but it is not clear if it is beneficial in COPD. We investigated
the hypotheses that acute nitrate dosing would improve exercise performance and
reduce the oxygen cost of submaximal exercise in people with COPD. METHODS: We
performed a double-blind, placebo-controlled, cross-over single dose study.
Subjects were randomised to consume either nitrate-rich beetroot juice
(containing 12.9 mmoles nitrate) or placebo (nitrate-depleted beetroot juice) 3
hours prior to endurance cycle ergometry, performed at 70% of maximal workload
assessed by a prior incremental exercise test. After a minimum washout period of
7 days the protocol was repeated with the crossover beverage. RESULTS: 21
subjects successfully completed the study (age 68 ± 7 years; BMI 25.2 ± 5.5
kg/m2; FEV1 percentage predicted 50.1 ± 21.6%; peak VO2 18.0 ± 5.9 ml/min/kg).
Resting diastolic blood pressure fell significantly with nitrate supplementation
compared to placebo (-7 ± 8 mmHg nitrate vs. -1 ± 8 mmHg placebo; p = 0.008).
Median endurance time did not differ significantly; nitrate 5.65 (3.90-10.40)
minutes vs. placebo 6.40 (4.01-9.67) minutes (p = 0.50). However, isotime oxygen
consumption (VO2) was lower following nitrate supplementation (16.6 ± 6.0
ml/min/kg nitrate vs. 17.2 ± 6.0 ml/min/kg placebo; p = 0.043), and consequently
nitrate supplementation caused a significant lowering of the amplitude of the
VO2-percentage isotime curve. CONCLUSIONS: Acute administration of oral nitrate
did not enhance endurance exercise performance; however the observation that
beetroot juice caused reduced oxygen consumption at isotime suggests that further
investigation of this treatment approach is warranted, perhaps targeting a more
hypoxic phenotype. TRIAL REGISTRATION: ISRCTN Registry ISRCTN66099139.
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