Abstract
- Background
Dietary inorganic nitrate (NO}_3^-$) supplementation via beetroot juice has been clinically established to enhance exercise capacity and physiological efficiency in both younger and older adults. However, its therapeutic utility in patients with chronic obstructive pulmonary disease (COPD)—a population characterized by severe exercise intolerance, systemic vascular dysfunction, and impaired oxidative capacity—remains an area of active investigation. This study was designed to investigate the physiological and functional effects of acute dietary nitrate ingestion on submaximal constant work rate exercise capacity and hemodynamic parameters in patients diagnosed with COPD.
- Methods
A randomized, single-blind, placebo-controlled crossover trial was conducted involving fifteen patients with COPD. Participants were randomly allocated to receive either acute nitrate-rich beetroot juice or a matched placebo in a counterbalanced sequence, with adequate washout periods between interventions. The primary clinical outcome measure was submaximal constant work rate exercise endurance time evaluated at 75% of each patient's predetermined maximal work capacity. Secondary outcomes encompassed plasma inorganic nitrate (NO}_3^-$) and nitrite (NO}_2^-$) concentrations, resting and exercise blood pressure, heart rate, oxygen consumption ({VO}_2$), dynamic hyperinflation, subjective dyspnea, and perceived leg discomfort.
- Results
Biochemical analyses confirmed that acute beetroot ingestion successfully elevated plasma nitrate concentrations by 938% and nitrite concentrations by 379% relative to the placebo condition. Concurrently, median constant work rate exercise time was significantly prolonged ($P = 0.031$) following beetroot juice ingestion compared to placebo (375.0 $\pm$ 257.0 vs. 346.2 $\pm$ 148.0 seconds, respectively). Hemodynamically, beetroot supplementation led to significant reductions in diastolic blood pressure at iso-time ($P = 0.001$, a decrease of 6.4 mm Hg) and at the end of exercise ($P = 0.008$, a decrease of 5.6 mm Hg). Furthermore, resting systolic blood pressure was significantly lowered ($P = 0.019$) by 8.2 mm Hg during the beetroot trial relative to placebo. No statistically significant differences between the beetroot and placebo trials were observed for oxygen consumption, dynamic hyperinflation, heart rate, or subjective symptom scores for dyspnea and leg discomfort.
- Conclusions
Acute dietary nitrate supplementation via beetroot juice significantly elevates circulating plasma nitrate and nitrite, prolongs submaximal exercise endurance time, and reduces systemic blood pressure in patients with COPD, supporting its potential as an effective acute ergogenic and cardiovascular adjunct in pulmonary rehabilitation.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4411191/