The Effects of Dietary Nitrate Supplementation on the Oxygen Cost of Moderate-Intensity Exercise and Functional Capacity in Mild-Moderate COPD Patients

Patients with moderate chronic obstructive pulmonary disease (COPD) typically have reduced exercise capacity. This is because their lungs are damaged and because of increased work of breathing. In some patients, exercise capacity is reduced to such a level that even simple activities of daily living, such as washing and dressing, may impose a challenge.

Recent findings in healthy young people suggest that increasing the amount of nitrate in our diet in the form of beetroot juice can improve the ability to exercise. Studies involving cycling have shown that less oxygen is needed to perform the same level of exercise after taking more nitrate in the diet. Nitrate (found in abundance in beetroot) is known to be converted in the body to nitric oxide (NO), a substance which increases blood flow and may affect the energy-producing mechanisms inside muscle cells. A recent exciting finding is that such dietary nitrate supplementation appears to reduce the amount of oxygen needed to complete moderate intensity exercise (walking) in healthy individuals. It is the purpose of this study to see if such effects could be seen in COPD patients. If this is indeed the case, then it may suggest that a period of dietary supplementation of a relatively cheap, widely available, and natural food product may improve the ability of patients to undergo everyday tasks and ultimately improve their quality of life.

To help investigators understand the effects of dietary nitrate supplementation on the ability to exercise in COPD patients, the investigators will recruit 15 people with mild to moderate disease. They will complete a series of undemanding exercise tests on three separate occasions. On one occasion they will have had a course of nitrate rich beetroot juice leading up to the tests, and on the other occasion they will have had a course of beetroot juice with the nitrate removed. The investigators will monitor blood pressure, levels of nitrate and nitrite in the blood, oxygen uptake and functional capacity during the tests which will allow us to assess any effects that may have occurred as a result of increased nitrate intake.