Efficacy of dietary nitrate-rich beetroot juice supplementation in patients with chronic obstructive pulmonary disease (COPD): A systematic review and meta-analysis

Summary Background Chronic Obstructive Pulmonary Disease (COPD) is a chronic inflammatory lung disease causing airflow obstruction from the lungs reducing exercise tolerance. It is one of the leading causes of respiratory dysfunction worldwide. Nitric Oxide (NO) may have a significant role in this inflammatory reaction to improve exercise capacity. Aim To evaluate the effect of dietary nitrate ingestion for COPD patients. Methods We searched Scopus, PubMed, Cochrane, and Web of Science databases till August 2020 and updated the search in December 2020 using relevant keywords. All search results were screened for eligibility. We extracted the data from the included articles and pooled them as mean difference (MD) with a 95% confidence interval (CI), using Review Manager software (ver. 5.4). Results A pooled analysis from eight included trials showed no significant difference between dietary nitrate-rich beetroot juice and placebo in systolic blood pressure, diastolic blood pressure, heart rate, 6-minute walk test, cycling ergometry endurance time, and maximum rate of oxygen consumption (VO2). On the other hand, nitrate-rich beetroot juice significantly increased the Borg Rating of Perceived Exertion (RPE) scale more than the placebo (MD = -0.77; 95% CI [0.18, 1.37], P = 0.01). Conclusion There is no significant effect of nitrate-rich beetroot juice on cardiovascular events as systolic, diastolic blood pressure, and heart rate, or exercise performance as 6-minute walk test, and cycling ergometry endurance time, or maximum rate of oxygen consumption (VO2). On the other hand, nitrate-rich beetroot juice improves the Borg Rating of Perceived Exertion (RPE) scale reflecting an increased exercise and physical activity level.