Dietary nitrate improved exercise capacity in COPD but not blood pressure or pulmonary function: a 2 week, double-blind randomised, placebo-controlled crossover trial

Dietary Beetroot Juice - Effects in Patients with COPD: A Review

Chronic Obstructive Pulmonary Disease (COPD) exerts a severe toll on human health and the economy, with high prevalence and mortality rates. The search for bioactive components effective in the treatment of COPD has become a focal point of research. Beetroot juice, readily accessible and cost-effective, is noted for its ability to enhance athletic performance and for its preventive and therapeutic impact on hypertension. Beetroot juice is a rich source of dietary nitrates and modulates physiological processes via the nitrate-nitrite- nitric oxide pathway, exerting multiple beneficial effects such as antihypertensive, bronchodilatory, anti-inflammatory, antioxidant, hypoglycemic, and lipid-lowering actions. This paper provides a review of the existing research on the effects of beetroot juice on COPD, summarizing its potential in enhancing exercise capacity, lowering blood pressure, improving vascular function, and ameliorating sleep quality among patients with COPD. The review serves as a reference for the prospective use of beetroot juice in the symptomatic improvement of COPD, as well as in the prevention of exacerbations and associated comorbidities.

The Role of Nutrition in the Development and Management of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a prevalent lung condition associated with significant morbidity and mortality. The management of COPD classically involves pulmonary rehabilitation, bronchodilators, and corticosteroids. An aspect of COPD management that is currently lacking in the literature is nutritional management, despite the prevalence of inadequate nutritional status in patients with COPD. In addition, certain nutritional imbalances have been reported to increase the risk of COPD development. This review summarizes the current literature on the role diet and nutrients may play in the risk and management of COPD development.

Dietary nitrate supplementation to enhance exercise capacity in patients with COPD: Evidence from a meta-analysis of randomized controlled trials and a network pharmacological analysis

OBJECTIVE

The potential effects of nitrate in patients with chronic obstructive pulmonary disease (COPD) have attracted increased research interest. However, previous clinical trials have reported inconsistent results, and consecutive meta-analyses have failed to reach a consensus. Since some randomized controlled trials have recently been conducted that can provide more evidence, we performed an updated meta-analysis.

METHODS

A comprehensive literature search was conducted using PubMed, the Cochrane Library, Embase, and Web of Science databases to identify trials that assessed the efficacy and safety of nitrate in patients with COPD. The Revman 5.3 software was used for data analysis. Mean difference (MD) or standardized mean difference (SMD) with 95 % confidence interval (CI) was used as the effect measure, and forest plots were used to display individual and pooled results. Network pharmacology analysis was conducted to investigate the potential mechanisms of nitrate action in COPD.

RESULTS

Eleven studies involving 287 patients were included in this meta-analysis. The results indicated that dietary nitrate supplementation increased plasma nitrate and nitrite concentrations and fractional exhaled nitric oxide in patients with COPD. Nitrate improved exercise capacity [SMD = 0.38, 95 % CI = 0.04-0.72] and endothelial function [MD = 9.41, 95 % CI = 5.30-13.52], and relieved dyspnea in patients with COPD. Network pharmacology identified AKT1, IL1B, MAPK3, and CASP3 as key treatment targets.

CONCLUSION

Dietary nitrate supplementation could be used as a potential treatment for patients with COPD, especially to increase their exercise capacity. The underlying mechanisms may be related to AKT1, IL1B, MAPK3, and CASP3.

The Possible Role of Food and Diet in the Quality of Life in Patients with COPD-A State-of-the-Art Review

Diet has been described as a modifiable risk factor for the development and progression of chronic diseases, and emerging evidence increasingly points to its preventive and therapeutic role in chronic obstructive pulmonary disease (COPD). While the relationship between the underlying disease and diet is natural in conditions such as metabolic disorders, obesity, diabetes, etc., the direct effect is not so evident in chronic obstructive pulmonary disease. Poor diet quality and the development of nutrient deficiencies in respiratory diseases, including COPD, can be associated with disease-specific factors such as the exacerbation of respiratory symptoms. These symptoms can be improved by dietary interventions, leading to positive changes in the pathogenesis of the disease and the quality of life of patients. Therefore, our aim was to review the latest randomized controlled trials (RCTs) of dietary interventions in chronic respiratory patients and describe their effects on respiratory function, physical activity, systemic inflammatory parameters, and quality of life. We conducted a literature search on dietary interventions for COPD patients in the PubMed, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials (CENTRAL) databases, focusing on publications from 1 July 2018 to 1 July 2023. We used specific keywords and MESH terms, focusing on RCTs. A total of 26 articles and 1811 COPD patients were included in this review. On the basis of our findings, dietary interventions, in particular components of the Mediterranean diet such as protein, omega-3 polyunsaturated fatty acids, and vegetables, appear to have beneficial effects in patients with chronic respiratory diseases, and their application is beneficial. However, long-term follow-up studies are still needed to examine the effects of dietary interventions in this patient population.

Strategies targeting the NO pathway to counteract extra-pulmonary manifestations of COPD: A systematic review and meta-analysis

The clinical symptoms of chronic obstructive pulmonary disease (COPD) disease are accompanied by severely debilitating extra-pulmonary manifestations, including vascular dysfunction and hypertension. This systematic review evaluated the current evidence for several therapeutic interventions, targeting the nitric oxide (NO) pathway on hemodynamics and, secondarily, exercise capacity in patients with COPD. A comprehensive search on COPD and NO donors was performed on online databases. Of 934 initially found manuscripts, 27 were included in the review, and 16 in the meta-analysis. The analysis indicated inconsistent effects of dietary nitrate supplementation on exercise tolerance in COPD patients. Dietary nitrate supplementation decreased systolic (-3.7 ± 4.3 mmHg; p = 0.10) and diastolic blood pressure (BP; -2.6 ± 3.2 mmHg; p = 0.05) compared with placebo. When restricted to acute studies, a clinically relevant BP lowering effect of nitrate supplementation during diastole was observed (-4.7 ± 3.2 mmHg; n = 5; p = 0.05). In contrast, inhaled NO (iNO) at doses <20 ppm (+9.2 ± 11.3 mmHg) and 25-40 ppm (-5±2 mmHg) resulted in inconsistent effects on PaO₂ (p = 0.48). Data on the effect of iNO on exercise capacity were too limited and inconsistent, but preliminary evidence suggests a possible benefit of iNO on pulmonary vascular resistance during exercise in severe COPD patients. Overall, the effects of acute dietary nitrate supplementation on BP may be of clinical relevance as an adjunct therapy and deserve further investigation in large sample size studies of COPD patients with and without cardiovascular comorbidities. iNO exerted inconsistent physiological effects, with the use of high doses posing safety risks.

Inorganic nitrate supplementation and blood flow restricted exercise tolerance in post-menopausal women

Exercise tolerance appears to benefit most from dietary nitrate (NO3-) supplementation when muscle oxygen (O2) availability is low. Using a double-blind, randomized cross-over design, we tested the hypothesis that acute NO3- supplementation would improve blood flow restricted exercise duration in post-menopausal women, a population with reduced endogenous nitric oxide bioavailability. Thirteen women (57-76 yr) performed rhythmic isometric handgrip contractions (10% MVC, 30 per min) during progressive forearm blood flow restriction (upper arm cuff gradually inflated 20 mmHg each min) on three study visits, with 7-10 days between visits. Approximately one week following the first (familiarization) visit, participants consumed 140 ml of NO3- concentrated (9.7 mmol, 0.6 gm NO3-) or NO3-depleted beetroot juice (placebo) on separate days (≥7 days apart), with handgrip exercise beginning 100 min post-consumption. Handgrip force recordings were analyzed to determine if NO3- supplementation enhanced force development as blood flow restriction progressed. Nitrate supplementation increased plasma NO3- (16.2-fold) and NO2- (4.2-fold) and time to volitional fatigue (61.8 ± 56.5 s longer duration vs. placebo visit; p = 0.03). Nitrate supplementation increased the rate of force development as forearm muscle ischemia progressed (p = 0.023 between 50 and 75% of time to fatigue) with non-significant effects thereafter (p = 0.052). No effects of nitrate supplementation were observed for mean duration of contraction or relaxation rates (all p > 0.150). These results suggest that acute NO3- supplementation prolongs time-to-fatigue and speeds grip force development during progressive forearm muscle ischemia in postmenopausal women.

Efficacy and safety of nitrate supplementation on exercise tolerance in chronic obstructive pulmonary disease: A systematic review and meta-analysis

BACKGROUND

Exercise intolerance was prevalent in people with chronic obstructive pulmonary disease (COPD) and had a detrimental effect on the quality of life. We aimed to evaluate the efficacy and safety of nitrate supplementation in exercise tolerance of people with COPD.

METHODS

We searched medical databases including Cochrane Library, EMBASE, and PubMed from inception to October 2020 for randomized control trials in treating COPD with nitrate supplementation.

RESULTS

Nine trials were identified. Compared with placebo, nitrate supplementation has no significant effect on the following variables: exercise endurance time (standard mean difference [SMD]: 0.06; 95% confidence interval [CI]: -0.39 to 0.52; P = .79), exercise capacity (SMD: 0.30; 95% CI: -0.21 to 0.80; P = .25), oxygen consumption (SMD: -0.04; 95% CI: -0.33 to 0.25; P = .80), resting systolic blood pressure (MD: -2.84; 95% CI: -8.46 to 2.78; P = .32), systolic blood pressure after exercise (MD: -4.66; 95% CI -15.66 to 6.34; P = .41), resting diastolic blood pressure (MD: 0.89; 95% CI: -4.41 to 6.19; P = .74), diastolic blood pressure after exercise (MD: -0.21; 95% CI: -5.51 to 5.10; P = .94), heart rate (MD: -2.52; 95% CI: -7.76 to 2.73; P = .35), and arterial oxygen saturation (MD: -0.44; 95% CI: -2.38 to 1.49; P = .65). No severe adverse effects from nitrate supplementation were reported in the included trails.

CONCLUSION

Current evidence suggests that nitrate supplementation may be safe but ineffective for improving exercise tolerance in people with COPD.

Effects of Nutritional Interventions in Individuals with Chronic Obstructive Lung Disease: A Systematic Review of Randomized Controlled Trials

Background

The role of nutrition and dietary patterns has been widely investigated in cancer, cardiovascular disease, and diabetes, but there are limited data on nutritional impact on COPD. This systematic review (PROSPERO-reg. no: CRD42020172712) aimed to investigate the effect of nutritional interventions on pulmonary and physical function, inflammation, and health-related quality of life among individuals with COPD.

Methods

Systematic searches were conducted in Medline, Embase, and Cochrane, resulting in 3861 references. Studies focusing exclusively on inpatient-stays, underweight or obese patients were excluded. Double screening, extraction and bias assessment were conducted. Bias was assessed according to the Cochrane risk of bias tool for randomized controlled trials. Thirteen randomized controlled trials with 916 participants were included.

Results

These trials investigated effects of protein supplementation, beetroot juice, increased fruit and vegetable intake, black seed oil, Tualang honey, Chlorella vulgaris-extract, whey-peptide containing nutritional drink, and increased macronutrient intake. The durations of the interventions were from weeks to a few months, and only one with duration >1 year (investigating increased fruit/vegetable intake). The intervention increasing fruit/vegetables found improvement in pulmonary function tests. Some interventions observed effects on systemic inflammation, health-related quality of life and physical function, although with some mixed results. Five were classified as poor, five as fair, and three as good in terms of risk of bias and quality.

Conclusion

Increasing intake of fruits and vegetables over prolonged periods might have positive effects on lung function in individuals with COPD. Some nutritional interventions also observed effects on systemic inflammation, health-related quality of life, and physical function, although with some mixed results. Many of the trials were underpowered, had high dropout rates, or had a high risk of bias. Further research should investigate effect of prolonged dietary interventions.

Impact of dietary nitrate supplementation on exercise capacity and cardiovascular parameters in chronic respiratory disease: a systematic review and meta-analysis

Background

Dietary nitrate supplementation, usually in the form of beetroot juice, may improve exercise performance and endothelial function. We undertook a systematic review and meta-analysis to establish whether this approach has beneficial effects in people with respiratory disease.

Methods

A systematic search of records up to March 2021 was performed on PubMed, CINAHL, MEDLINE (Ovid), Cochrane and Embase to retrieve clinical trials that evaluated the efficacy of dietary nitrate supplementation on cardiovascular parameters and exercise capacity in chronic respiratory conditions. Two authors independently screened titles, abstracts and full texts of potential studies and performed the data extraction.

Results

After full-text review of 67 papers, eleven (two randomised controlled trials and nine crossover trials) involving 282 participants met the inclusion criteria. Three were single dose; seven short term; and one, the largest (n=122), done in the context of pulmonary rehabilitation. Pooled analysis showed that dietary nitrate supplementation reduced systolic blood pressure (BP), diastolic BP and mean arterial pressure (mean difference (95% CI), −3.39 mm Hg (−6.79 to 0.01); p=0.05 and –2.20 mm Hg (−4.36 to −0.03); p=0.05 and −4.40 mm Hg (−7.49 to −1.30); p=0.005, respectively). It was associated with increased walk distance in the context of pulmonary rehabilitation (standardised mean difference (95% CI), 0.47 (0.11 to 0.83), p=0.01), but no effect was identified in short-term studies (0.08 (−0.32 to 0.49).

Conclusion

Dietary nitrate supplementation may have a beneficial effect on BP and augment the effect of pulmonary rehabilitation on exercise capacity. Short-term studies do not suggest a consistent benefit on exercise capacity.

PROSPERO registration number

CRD42019130123.

Daily Vegetables Intake and Response to COPD Rehabilitation. The Role of Oxidative Stress, Inflammation and DNA Damage

Chronic obstructive pulmonary disease (COPD) is a respiratory disease associated with airways inflammation and lung parenchyma fibrosis. The primary goals of COPD treatment are to reduce symptoms and risk of exacerbations, therefore pulmonary rehabilitation is considered the key component of managing COPD patients. Oxidative airway damage, inflammation and reduction of endogenous antioxidant enzymes are known to play a crucial role in the pathogenesis of COPD. Recently, also natural antioxidants have been considered as they play an important role in metabolism, DNA repair and fighting the effects of oxidative stress. In this paper we evaluated the response of 105 elderly COPD patients to pulmonary rehabilitation (PR), based on high or low vegetable consumption, by analyzing clinical parameters and biological measurements at baseline and after completion of the three weeks PR. We found that daily vegetable intake in normal diet, without any specific intervention, can increase the probability to successfully respond to rehabilitation (65.4% of responders ate vegetables daily vs. 40.0% of non-responders, p = 0.033). The association was especially evident in subjects ≥ 80 year of age (OR = 17.0; p < 0.019). Three weeks of pulmonary rehabilitation are probably too short to reveal a reduction of the oxidative stress and DNA damage, but are enough to show an improvement in the patient’s inflammatory state.

Boosting nitric oxide in stress and respiratory infection: Potential relevance for asthma and COVID-19

Nitric oxide (NO) is a ubiquitous signaling molecule that is critical for supporting a plethora of processes in biological organisms. Among these, its role in the innate immune system as a first line of defense against pathogens has received less attention. In asthma, levels of exhaled NO have been utilized as a window into airway inflammation caused by allergic processes. However, respiratory infections count among the most important triggers of disease exacerbations. Among the multitude of factors that affect NO levels are psychological processes. In particular, longer lasting states of psychological stress and depression have been shown to attenuate NO production. The novel SARS-CoV-2 virus, which has caused a pandemic, and with that, sustained levels of psychological stress globally, also adversely affects NO signaling. We review evidence on the role of NO in respiratory infection, including COVID-19, and stress, and argue that boosting NO bioavailability may be beneficial in protection from infections, thus benefitting individuals who suffer from stress in asthma or SARS-CoV-2 infection.

Effect of inorganic nitrate supplementation on blood pressure in older adults: A systematic review and meta-analysis

BACKGROUND

Previous clinical studies have shown controversial results regarding the effect of inorganic nitrate supplementation on blood pressure (BP) in older individuals. We performed this systematic review and meta-analysis to assess the effect of inorganic nitrate on BP in older adults.

METHODS

Eligible studies were searched in Cochrane Library, PubMed, Scopus, Web of Science, and Embase. Randomized controlled trials which evaluated the effect of inorganic nitrate consumption on BP in older adults were recruited. The random-effect model was used to calculate the pooled effect sizes.

RESULTS

22 studies were included in this meta-analysis. Overall, inorganic nitrate consumption significantly reduced systolic blood pressure (SBP) by -3.90 mmHg (95% confidence interval: -5.23 to -2.57; P < 0.001) and diastolic blood pressure (DBP) by -2.62 mmHg (95% confidence interval: -3.86 to -1.37; P < 0.005) comparing with the control group. Subgroup analysis showed that the BP was significantly reduced when participants' age≥65, BMI>30, or baseline BP in prehypertension stage. And both SBP and DBP decreased significantly after acute nitrate supplementation of a single dose (<1 day) or more than 1-week. However, participants with hypertension at baseline were not associated with significant changes in both SBP and DBP. Subgroup analysis of measurement methods showed that only the resting BP group showed a significant reduction in SBP and DBP, compared with the 24-h ambulatory BP monitoring (ABPM) group and daily home BP measurement group.

CONCLUSION

These results demonstrate that consuming inorganic nitrate can significantly reduce SBP and DBP in older adults, especially in whose age ≥ 65, BMI＞30, or baseline BP in prehypertension stage.

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

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-min 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-min 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.

Effect of Dietary Nitrate Supplementation on Sleep in Chronic Obstructive Pulmonary Disease Patients

PURPOSE

Poor sleep quality in chronic obstructive pulmonary disease (COPD) is a result of oxygen desaturation secondary to compromised lung function. Nitrate supplementation with dietary beetroot juice is known to elevate plasma nitrate and to increase the efficiency of oxygen utilization in non-COPD individuals; whether it is of therapeutic benefit for sleep quality in COPD has not been reported.

PATIENTS AND METHODS

In a counterbalanced within-subjects design involving 15 COPD patients as subjects, the subjects consumed either beetroot juice containing nitrate (BJ; ∼6.2 mmol NO₃ ^-) or placebo (NO₃ ^- -depleted juice) immediately before a night of polysomnographic monitoring. Nitrate was measured in plasma collected immediately after waking.

RESULTS

While BJ consumption had no effect on the amount of time spent in any sleep stages, wake-to-N2 transitions and direct wake-to-rapid eye movement sleep (REMS) transitions, hallmarks of disordered sleep, were less frequent on the BJ night than on the placebo night. In the last two hours of the BJ night, percent time in REMS increased and delta power during deep (N3) non-REMS decreased, relative to the placebo night. Collectively, the reduced frequency of atypical transitions and the normalization of non-REMS/REMS dynamics after BJ are indicative of an improvement of sleep quality. BJ also resulted in sustained elevation of peripheral oxygen saturation (SpO₂), during episodes of wake after sleep onset. Plasma nitrate was elevated nearly tenfold on the morning after BJ relative to placebo.

CONCLUSION

BJ has a normalizing effect on disordered sleep in COPD, which may be related to improved oxygen delivery.

CLINICAL TRIAL REGISTRATION

The activities of the Regional Committees for Medical and Health Research Ethics (REC) are founded on the Norwegian law on research ethics and medical research. This study was approved by NTNU/REK midt, Det medisinske fakultet, Postboks 8905, 7491 Trondheim (REK midt 2016/1360).

Oral nitrate supplementation to enhance pulmonary rehabilitation in COPD: ON-EPIC a multicentre, double-blind, placebo-controlled, randomised parallel group study

RATIONALE

Dietary nitrate supplementation has been proposed as a strategy to improve exercise performance, both in healthy individuals and in people with COPD. We aimed to assess whether it could enhance the effect of pulmonary rehabilitation (PR) in COPD.

METHODS

This double-blind, placebo-controlled, parallel group, randomised controlled study performed at four UK centres, enrolled adults with Global Initiative for Chronic Obstructive Lung Disease grade II-IV COPD and Medical Research Council dyspnoea score 3-5 or functional limitation to undertake a twice weekly 8-week PR programme. They were randomly assigned (1:1) to either 140 mL of nitrate-rich beetroot juice (BRJ) (12.9 mmol nitrate), or placebo nitrate-deplete BRJ, consumed 3 hours prior to undertaking each PR session. Allocation used computer-generated block randomisation.

MEASUREMENTS

The primary outcome was change in incremental shuttle walk test (ISWT) distance. Secondary outcomes included quality of life, physical activity level, endothelial function via flow-mediated dilatation, fat-free mass index and blood pressure parameters.

RESULTS

165 participants were recruited, 78 randomised to nitrate-rich BRJ and 87 randomised to placebo. Exercise capacity increased more with active treatment (n=57) than placebo (n=65); median (IQR) change in ISWT distance +60 m (10, 85) vs +30 m (0, 70), estimated treatment effect 30 m (95% CI 10 to 40); p=0.027. Active treatment also impacted on systolic blood pressure: treatment group -5.0 mm Hg (-5.0, -3.0) versus control +6.0 mm Hg (-1.0, 15.5), estimated treatment effect -7 mm Hg (95% CI 7 to -20) (p<0.0005). No significant serious adverse events or side effects were reported.

CONCLUSIONS

Dietary nitrate supplementation appears to be a well-tolerated and effective strategy to augment the benefits of PR in COPD.

TRIAL REGISTRATION NUMBER

ISRCTN27860457.

Physiological Effects of Beetroot in Athletes and Patients

Dietary supplementation with beetroot juice (BRJ), a naturally rich source of nitrate, is an area of considerable interest to elite athletes as well as recreational exercisers. Nitrate and nitrite have previously been thought of as mainly final elimination products of nitric oxide (NO), but this view has been challenged and evidence indicates that these compounds can be converted to NO in vivo. We conducted a narrative review summarizing the literature regarding evidence of beetroot used as dietary supplement and its effects on training physiology and athletic performance in healthy and diseased populations. The databases PubMed and Web of Science were used to obtain articles. It was evident that BRJ supplementation had an effect on oxygen cost and consumption during exercise by more efficient adenosine triphosphate (ATP) production in combination with lower ATP consumption. However, the effect seems to be dependent on dose and duration. Effect on exercise performance is conflicting, time to exhaustion seems to increase but its effect on time-trial performance needs further elucidation. Ergogenic benefits might depend on individual aerobic fitness level, where individuals with lower fitness level may gain higher benefits regarding athletic performance. Dietary nitrate supplementation appears to have some effect on training performance in patients with peripheral artery disease, heart failure, and chronic pulmonary obstructive disease. However, larger randomized controlled trials are necessary to determine the overall utility of beetroot as a dietary supplement.