Dietary beetroot juice – effects on physical performance in COPD patients: a randomized controlled crossover trial

Abstract

Background and objective

Dietary beetroot juice (BR) supplementation has been shown to reduce the oxygen (O₂) consumption of standardized exercise and reduce resting blood pressure (BP) in healthy individuals. However, the physiological response of BR in chronic obstructive pulmonary disease (COPD) remains controversial. The objective was to test exercise performance in COPD, supplementing with higher doses of BR for a longer duration compared to previous trials in this patient group.

Methods

Fifteen COPD patients consumed concentrated BR (2×70 mL twice daily, each containing 300 mg nitrate) or placebo (PL) (2×70 mL twice daily, nitrate-negligible) in a randomized order for 6 consecutive days. On day 7, participants consumed either BR or PL 150 min before testing. BP was measured before completing 6-minute walk test (6MWT) and two trials of submaximal cycling. The protocol was repeated after a minimum washout of 7 days.

Results

Plasma nitrite concentration was higher in the BR condition compared to PL (P<0.01). There was no difference between the BR and PL conditions regarding the covered distance during the 6MWT (mean ± standard error of the mean: 515±35 m (BR) vs 520±38 m (PL), P=0.46), O₂ consumption of submaximal exercise (trial 1 P=0.31 vs trial 2 P=0.20), physical activity level (P>0.05), or systolic BP (P=0.80). However, diastolic BP (DBP) was reduced after BR ingestion compared to baseline (mean difference: 4.6, 95% CI: 0.1–9.1, P<0.05).

Conclusion

Seven days of BR ingestion increased plasma nitrite concentrations and lowered DBP in COPD patients. However, BR did not increase functional walking capacity, O₂ consumption during submaximal cycling, or physical activity level during the intervention period.

Keywords:

• nitric oxide
• chronic obstructive pulmonary disease
• exercise
• nitrate
• beetroot juice
• blood pressure
• nitrite

Acknowledgments

The authors would like to thank all of the study participants for their time, dedication, and enthusiasm. In addition, we thank the employees at the Department of Respiratory Diseases and Allergy, Aarhus University Hospital for their help with recruitment of participants and Professor, MD, Thorsten Ingemann Hansen from the Section of Sport Science, Department of Public Health, Aarhus University, for his medical expertise. We would also like to acknowledge the laboratory technicians Janni Mosgaard Jensen and Gitte Kaiser Hartvigsen for their ineffable expertise and help during laboratory work and data collection and Ulf Simonsen who analyzed the serum samples for NO₂⁻. Additionally, we would like to thank Thomas Maribo for his guidance in choosing relevant physiological tests for the trial. The trial is funded by Krista and Viggos Foundation (DKK 35,000).

Disclosure

The authors report no conflicts of interest in this work.