Dietary nitrate supplementation in COPD: An acute, double-blind, randomized, placebo-controlled, crossover trial

• Beetroot juice is a rich source of dietary nitrate.
• Acute consumption of beetroot juice was associated with increased exercise capacity among COPD subjects.
• Serum nitrate and nitrite increased significantly after dietary nitrate only.
• Similarly, blood pressure decreased significantly after dietary nitrate only.
• The clinical application of dietary nitrate in COPD requires further study.

BackgroundThe acute consumption of dietary nitrate has been shown to improve exercise capacity in athletes, healthy adults and subjects with peripheral vascular disease. Many COPD patients have reduced exercise capacity. We hypothesized that acute nitrate consumption might increase incremental shuttle walk test (ISWT) distance in COPD subjects.MethodsEleven COPD subjects were randomly assigned to consume either a high nitrate or a matched, low nitrate beverage in a double-blind, randomized, placebo-controlled, crossover design. ISWT distance was measured both before and 3 h after the beverage and change was recorded. After a 7-day washout, ISWT distances were re-measured before and 3 h after the alternate beverage and changes were recorded.ResultsWe observed an increase in ISWT distance after consuming the high nitrate juice (25 m) compared with a reduction after the low nitrate juice (14 m) (p < 0.01). This improvement in exercise capacity was associated with significant increases in serum nitrate (p < 0.000005) and nitrite (p < 0.01) levels and a significant lowering of resting blood pressure (<0.05).ConclusionsIn patients with stable COPD, the acute consumption of dietary nitrate increased serum nitrate/nitrite levels and exercise capacity and was associated with a decrease in resting blood pressure. Nitrate consumption might alter exercise capacity in COPD patients.