Acute Dietary Nitrate Supplementation and Exercise Performance in COPD: A Double-Blind, Placebo-Controlled, Randomised Controlled Pilot Study

PLoS ONE
Q1
Dec 2015
Citations:58
Influential Citations:5
Interventional (Human) Studies
82
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Enhanced Details

Methods
Double-blind, cross-over, placebo-controlled trial in COPD patients (GOLD stage II–IV). 21 completed; mean age 68 ± 7 years; BMI 25.2 ± 5.5 kg/m2; FEV1 50.1 ± 21.6% predicted; peak VO2 18.0 ± 5.9 mL/min/kg.
Intervention
140 ml beetroot juice containing 12.9 mmol nitrate (≈0.8 g) taken 3 hours before endurance cycle ergometry; placebo beverage was 140 ml nitrate-depleted beetroot juice with identical appearance and taste, taken 3 hours before testing.
Results
Nitrate-rich beetroot juice did not significantly improve endurance time at 70% peak workload (5.65 min [3.90–10.40] vs 6.40 min [4.01–9.67], p=0.50). Resting diastolic BP decreased more with nitrate (−7±8 mmHg) than placebo (−1±8 mmHg; p=0.008). Plasma nitrate rose from baseline ~37 μM to ~820 μM after dosing; nitrite rose to ~1.57 μM. Isotime VO2 and minute ventilation were lower with nitrate, indicating a lower oxygen cost of submaximal exercise; VO2 curves diverged by isotime and the area under the VO2 isotime curve was smaller with nitrate. Authors conclude that a single high-dose nitrate dose is biologically active but does not improve endurance in COPD; potential benefits may exist in particular COPD phenotypes or as an adjunct to rehabilitation; further research is warranted.
Limitations
Small sample size (n=21 completed); acute single-dose design; day-to-day variability in COPD endurance may reduce power to detect changes; not tested in oxygen-requiring COPD; possible inter-individual variability in nitrate responsiveness; findings may not generalize to longer-term supplementation.

Abstract

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...