Oxygenation of skeletal muscle and endothelial function is enhanced by dietary nitrate supplementation. Using these effects, the researchers hypothesized that patients with COPD and hypoxia severe enough to require supplemental oxygen might improve their exercise performance.

COPD sufferers may develop hypoxemia as their condition worsens, affecting their daily functioning. As a result of chronic obstructive pulmonary disease (COPD), your lungs may not be able to breathe well. This can cause hypoxia, which is when your body doesn’t get enough oxygen to the cells and tissues.

Various mechanisms contribute to this condition, including ventilation-perfusion mismatch, reduced cardiac output, pulmonary vascular limitation, and reduced muscle efficiency. On the other hand, LTOT improves survival in sufficiently hypoxaemic individuals, and ambulatory oxygen therapy (AOT) enhances exercise performance in many individuals.

Nitric oxide (NO) can be a modulator of exercise performance. S ubiquitous signaling molecule that participates in various processes at the tissue and cellular level, including mitochondrial and cell respiration, glucose uptake into the muscles, contractions, neurotransmission, and fatigue. 

A much more palatable option for nitrate in the diet is beetroot juice. In addition, cured and processed meats, as well as water, are sources of nitrate.

There are several bioactive compounds in beetroot besides nitrate, including phenolics, ascorbic acid, carotenoids, and betalains. In addition to increasing power output and endurance, betaine has been reported to act as an osmolyte that can increase resistance to stress as its intracellular concentrations increase.

As part of the study, adult COPD patients who had been using long-term oxygen therapy were enrolled in a single-center, double-blind, placebo-controlled cross-over study. 

Participants performed an endurance shuttle walk test with their prescribed oxygen three hours after consuming 140 mL of either nitrate-rich beetroot juice (BRJ) or nitrate-depleted BRJ (nitrate-depleted BRJ). The treatment order was assigned using a computer-generated block randomization system (1:1).

An endurance shuttle walk test time was the primary outcome. Secondary outcomes included fingertip oxygen saturation area under the curve to time, heart rate parameters, blood pressure, and endothelial function assessed using flow-mediated dilatation. The researchers also evaluated plasma nitrate, nitrite, and FENO levels.

Results of the Study

The study recruited 20 participants, and all completed it. Nitrate-rich BRJ supplementation significantly increased exercise endurance times in all participants, compared with placebo: median (IQR) 194.6 vs. 159.1, estimated treatment effect. Additionally, the NR-BRJ group improved endothelial function compared to the placebo group.

The study’s results indicate that acute dietary nitrate supplementation increases exercise endurance in chronic obstructive pulmonary disease patients requiring supplemental oxygen.

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