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

Abstract

Background and objectiveDietary 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.MethodsFifteen 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.ResultsPlasma 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).ConclusionSeven 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.

The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway

“…Two separate studies have shown that acute supplementation of dietary nitrate (7.6-12.9 mmol nitrate) improves 75% submaximal exercise time by 30 seconds and incremental shuttle walk test by 40 m compared with placebo (Berry et al, 2015;Kerley et al, 2015); in contrast, however, further studies using 13.5 mmol nitrate daily for 2.5 days (Shepherd et al, 2015b) or 20 mmol nitrate for 6 days (Friis et al, 2017) showed no benefit on the O 2 cost of exercise or 6-minute walk test (Shepherd et al, 2015b;Friis et al, 2017). Importantly, in these studies, plasma nitrite levels were increased, and BP was robustly reduced, suggesting that both the chemical and functional effects of the nitrate-nitrite-•NO pathway are present in patients with COPD.…”

Role of Diet in Chronic Obstructive Pulmonary Disease Prevention and Treatment

“…In a small 12-week randomized trial including moderate-to-severe COPD patients complying with an intervention to increase fruit intake, no improvement in airways or systemic inflammation and oxidative stress markers was observed, although the follow-up might have been too short to observe any significant effect [57]. In COPD patients, 1-week supplementation with beetroot juice, a dietary source of nitrates that improves mitochondrial respiration and energy production via nitric oxide formation, increased plasma nitrate levels and decreased diastolic blood pressure (mean difference 4.6 mmHg, 95% CI: 0.1, 9.1, p < 0.05) without any effect on walking capacity, physical activity level, or oxygen consumption of submaximal exercise [58]. However, another randomized trial reported that COPD patients following a diet rich in fruits and vegetables (>1 portion/day) showed an annual increase in FEV1 compared with the control group following a free diet over 3 years ( p = 0.03), after adjustment for physical activity, alcohol intake, co-morbidities, and exacerbation frequency [59].…”

Physiological Effects of Beetroot in Athletes and Patients

“…These results were not confirmed by another group, who did not observe a significant change in median time of exercise, but did find a lower oxygen cost during exercise [47]. Furthermore, other studies have measured oxygen cost and distance covered during a six-minute walking test, but without reporting significant changes in either upon consumption of BRJ [48][49][50]. Thus, larger trials would be needed to conclude the utility of BRJ in this patient population.…”