Nitrate-Rich Beetroot Juice Reduces Blood Pressure in Tanzanian Adults with Elevated Blood Pressure: A Double-Blind Randomized Controlled Feasibility Trial

Effects of beetroot juice on blood pressure in hypertension according to European Society of Hypertension Guidelines: A systematic review and meta-analysis

AIMS

It has been suggested that nitrate-rich beetroot juice (BRJ) reduces blood pressure (BP) in various populations. We aimed to investigate the effect of BRJ on BP in adults with hypertension according to the European Society of Hypertension Guidelines (clinical BP ≥ 140/≥ 90 mmHg) and whether BRJ can be considered as an adjunct to hypertension drug treatment, by conducting a meta-analysis of randomized controlled trials.

DATA SYNTHESIS

PubMed, SCOPUS, Medline Ovid, Cinahl, Cochrane Library and Web of Science were searched from inception until April 13, 2024 to identify randomized controlled trials of BRJ versus placebo, water, or no intake. Risk of bias was assessed using a standardized appraisal instrument from the Swedish Agency for Health Technology and Assessment of Social Services, which is based on the Cochrane risk-of-bias tool for randomized trials. The pooled BP effect size was calculated using random effects models and meta-regression. Certainty of evidence was assessed using GRADE. Eleven trials (349 patients) were included. BRJ yielded a significant reduction in clinical systolic BP compared with placebo mean difference (MD) -5.31 mmHg (95% CI -7.46, -3.16; I2 = 64%, GRADE ⊕⊕OO). There was no significant effect on clinical diastolic BP or 24-h BP outcomes, and the heterogeneity was moderate to high.

CONCLUSIONS

Daily ingestion of 200-800 mg of nitrate from BRJ may reduce clinical systolic BP in hypertensive individuals with no sign of development of tolerance. Certainty of evidence is low, and results should be interpreted with caution.

Evaluation of 12-Week Standardized Beetroot Extract Supplementation in Older Participants: A Preliminary Study of Human Health Safety

In recent years, there has been a notable surge in the popularity of beetroot-based dietary supplements, driven by their rich nitrate composition. Several types of beetroot-based dietary supplements can be found in markets worldwide; however, ensuring the safety of dietary supplements is a crucial consideration, as there is limited evidence on their safety, especially for older populations. Therefore, the purpose of the current study was to evaluate the safety and tolerability of a nitrate-rich beetroot extract in older participants taking supplements over 12 weeks. The participants were randomly assigned to receive 20 g daily of beetroot extract or a matching placebo. The safety and tolerability of the supplementation were evaluated as the occurrence of adverse events and anthropometric, biochemical, and hemodynamic parameters were measured. No serious adverse events were reported in any group. Anthropometric, biochemical, and hemodynamic parameter changes between the baseline and the end of the study were not statistically significant in either group. However, interestingly, the group receiving beetroot extract supplementation exhibited a notable increase in plasma nitrate levels (p = 0.076, f = 0.50) and showed a decrease in insulin levels (p = 0.026, f = 0.59). In conclusion, we found that 20 g of beetroot extract supplementation for 12 weeks was safe and well tolerated in older participants.

Associations between Vegetable Nitrate Intake and Cardiovascular Disease Risk and Mortality: A Systematic Review

Consumption of nitrate-rich vegetables increases nitric oxide bioavailability, lowers blood pressure, and improves endothelial function. These effects could also translate into reduced cardiovascular disease (CVD) risk and mortality. This systematic review aimed to investigate the associations between habitual vegetable nitrate intake and CVD incidence and mortality. A secondary aim was to identify factors that moderate the relationship between vegetable nitrate intake and CVD incidence/mortality. Seven databases (PubMed, MEDLINE, Embase, Scopus, Web of Science, CINAHL, and APA PsycINFO) were searched from inception to 13 February 2023. Observational studies quantifying vegetable nitrate intake in participants aged 18+ years through self-reported dietary exposure and assessing incidence or mortality from CVD overall, or individual CVD subtypes, were eligible. Five studies including a total of 63,155 participants were included. There was an inverse association between vegetable nitrate intake and most reported CVD outcomes. Reported risk reductions tended to plateau at moderate intake, suggesting a possible ceiling effect. The risk of bias across all studies was low. The results of this systematic review suggest a potential role for vegetable nitrate in reducing CVD risk and mortality. Further randomised controlled trials are now required to corroborate these findings.

The effects of beetroot and nitrate supplementation on body composition: a GRADE-assessed systematic review and meta-analysis

This systematic review and meta-analysis aimed to investigate the effects of beetroot (BR) or nitrate supplements on body composition indices. A systematic search was conducted for randomised controlled trials (RCT) published up to August 2022 among online databases including Scopus, PubMed/Medline, Web of Science and Embase. Meta-analyses were carried out using a random-effects model. The I2 index was used to assess the heterogeneity of RCT. A total of twelve RCT met the inclusion criteria for this meta-analysis. The pooled effect size of included studies indicated that BR or nitrate supplementation did not change body weight (weighted mean differences (WMD): -0·14 kg, 95 % CI -1·22, 1·51; P = 0·836; I2 = 0 %), BMI (WMD: -0·07 kg/m2, 95 % CI -0·19,0·03; P = 0·174, I2 = 0 %), fat mass (WMD: -0·26 kg, 95 % CI -1·51, 0·98; P = 0·677, I2 = 0 %), waist circumference (WMD: -0·28 cm, 95 % CI -2·30, 1·74; P = 0·786, I2 = 0 %), body fat percentage (WMD: 0·18 %, 95 % CI -0·62, 0·99; P = 0·651, I2 = 0 %), fat-free mass (WMD: 0·31 kg, 95 % CI -0·31, 1·94; P = 0·703, I2 = 0 %) and waist-to-hip ratio (WMD: 0, 95 % CI -0·01, 0·02; P = 0·676, I2 = 0 %). Subgroup analyses based on trial duration, BR or nitrate dose, study design, baseline BMI and athletic status (athlete v. non-athlete) demonstrated similar results. Certainty of evidence across outcomes ranged from low to moderate. This meta-analysis study suggests that BR or nitrate supplements cannot efficiently ameliorate body composition indices regardless of supplement dosage, trial duration and athletic status.

The impact of dietary and lifestyle interventions on blood pressure management in sub-Saharan Africa: a systematic review and metanalysis

OBJECTIVES

Current literature is lacking a comprehensive review of data on dietary interventions in blood pressure (BP) management in sub-Saharan African countries. We assessed the association of dietary and other lifestyle interventions with BP-lowering effects in populations within sub-Saharan Africa.

METHODS

We performed a systematic review and random-effects meta-analysis to determine the impact of dietary and lifestyle interventions on SBP and DBP in sub-Saharan Africa. We searched the MEDLINE, EMBASE, and Web of Science databases. We included intervention studies that were randomized and nonrandomized conducted in Africans residing in sub-Saharan Africa investigating diet and other lifestyle, physical activity, weight loss, tobacco, and alcohol cessation modifications. We determined the effect of diet and other lifestyle interventions on SBP and DBP. We expressed effect size as weighted mean difference and 95% confidence interval (CI).

MAIN RESULTS

: We identified six studies with a total of 1412 individuals, 38% males, mean age of 52.8 years (SD = 11.5). The weighted mean difference of dietary and other lifestyle interventions on SBP and DBP was -7.33 mmHg, (95% CI: -9.90 to -4.76, P  < 0.001) and -2.98 mmHg, (95% CI: -4.28 to -1.69, P  < 0.001), respectively. In the metaregression analyses, the duration of the interventions did not have any effect on changes in SBP and DBP.

PRINCIPAL CONCLUSION

: Dietary modifications showed a beneficial overall improvement in SBP and DBP in Africans. However, aside from low-salt interventions, studies on dietary potassium, healthy dietary patterns, and lifestyle modifications have not been investigated extensively in Africans and are in critical need. In addition, researchers will need to consider the settings (rural, urban, or semiurban) and the predominant existing dietary habits while designing studies on dietary interventions in sub-Saharan Africa.

PROSPERO REGISTRATION

CRD42020207923.

Regulatory effect of dietary nitrate on blood pressure: a meta-analysis of randomized controlled trials

Hypertension is the leading risk factor for global disease burden. Many clinical studies have reported that dietary inorganic nitrate can affect blood pressure. In this study, the PubMed, Embase, and Cochrane Library databases were searched for relevant literature published before December 2021 to explore the preventive and therapeutic effects of inorganic nitrate on hypertension. Two reviewers evaluated the randomized controlled trials of inorganic nitrates. This study included a total of 19 articles. The analyzed outcomes of the study were systolic, diastolic and mean arterial blood pressures as well as 24-hour ambulatory blood pressure. RevMan 5.4 was used to conduct meta-analysis. In the healthy population, inorganic nitrate lowered systolic blood pressure (-2.42 mmHg, 95% confidence intervals (CI) [-4.28, -0.57]; P = 0.01) but not diastolic blood pressure (-0.58 mmHg, 95% CI [-1.84, 0.68]; P = 0.36) or mean arterial pressure (-1.01 mmHg, 95% CI [-3.55, 1.54]; P = 0.44). However, in the hypertensive population, inorganic nitrates did not lower systolic blood pressure (-0.82 mmHg, 95% CI [-2.53, 0.90]; P = 0.35), diastolic blood pressure (-0.03 mmHg, 95% CI [-1.35, 1.30]; P = 0.97), 24-hour ambulatory systolic blood pressure (-0.22 mmHg, 95% CI [-1.50, 1.94]; P = 0.8), or 24-hour ambulatory diastolic blood pressure (-0.33 mmHg, 95% CI [-2.03, 1.37]; P = 0.7). In conclusion, inorganic nitrate can mildly reduce systolic blood pressure in healthy people, but does not have a lowering effect on blood pressure in patients with hypertension. Further research is required to obtain more definitive data and prove the link between inorganic nitrate and blood pressure.

Nitrate-rich beet juice intake on cardiovascular performance in response to exercise in postmenopausal women with arterial hypertension: study protocol for a randomized controlled trial

BACKGROUND

There is no evidence of the use of beetroot juice with a previously recommended dose of nitrate (NO3) (> 300 mg) on the cardiovascular performance during and recovery following exercise in postmenopausal women with systemic arterial hypertension (SAH).

METHODS

We will investigate the effects of beetroot juice rich in NO3 acutely (800 mg) and during a week with daily doses (400 mg) on blood pressure, heart rate (HR), cardiac autonomic control, endothelial function, inflammatory, hormonal, and stress biomarkers oxidative stress and enzymes involved in nitric oxide synthesis and mitochondrial regulation, under resting conditions, as well as mediated by submaximal aerobic exercise sessions. Through a randomized, crossover, triple-blind, placebo-controlled clinical trial, 25 physically inactive women with SAH will undergo an acute and 1-week trial, each with two intervention protocols: (1) placebo and (2) beetroot, in which will ingest beet juice with or without NO3 in its composition with a 7-day washout interval. On collection days, exercise will be performed on a treadmill for 40 min at a speed corresponding to 65-70% of VO2peak. The collection of variables (cardiovascular, autonomic, and blood samples for molecular analyses) of the study will take place at rest (135 min after ingestion of the intervention), during exercise (40 min), and in the effort recovery stage (during 60 min) based on previously validated protocols. The collections were arranged so that the measurement of one variable does not interfere with the other and that they have adequate intervals between them.

DISCUSSION

The results of this research may help in the real understanding of the nutritional compounds capable of generating safety to the cardiovascular system during physical exercise, especially for women who are aging and who have cardiovascular limitations (e.g., arterial hypertension) to perform physical exercise. Therefore, our results will be able to help specific nutritional recommendations to optimize cardiovascular health.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05384340. Registered on May 20, 2022.

Acute Effects of Dietary Nitrate on Central Pressure and Endothelial Function in Hypertensive Patients: A Randomized, Placebo-Controlled Crossover Study

BACKGROUND

The diet's inorganic nitrate (NO3-) may provide a physiological substrate for reducing nitrate (NO2-) to NO independent of the endothelium. Studies suggest that inorganic NO3- has beneficial effects on cardiovascular health.

OBJECTIVE

This study evaluated the acute effects of 500 mL nitrate-rich beetroot juice (BRJ; containing 11.5mmol NO3-) on blood pressure and endothelial function in treated hypertensive patients.

METHODS

A randomized, placebo-controlled, crossover study was conducted in treated hypertensive patients (n=37; women=62%) who underwent clinical and nutritional evaluation and assessment of central hemodynamic parameters and microvascular reactivity. The significance level was p<0.05.

RESULTS

The mean age was 59±7 years, and mean systolic and diastolic blood pressures were 142±10/83±9mmHg. There was a significant increase in the subendocardial viability ratio (SEVR; 149±25 vs. 165±30%, p<0.001) and reduction in ejection duration (ED; 37±4 vs. 34±4%, p<0.001) in the beetroot phase but no significant SEVR difference in the control phase. The % increase in perfusion (155 vs. 159 %, p=0.042) was significantly increased in the beetroot phase, which was not observed in the control phase. In the beetroot phase, the change in SEVR showed a significant correlation with the change in the area under the curve of post-occlusive reactive hyperemia (AUC-PORH) (r=0.45, p=0.012). The change in ED showed a significant correlation with the post-intervention perfusion peak (r=-0.37, p=0.031) and AUC-PORH (r=-0.36, p=0.046).

CONCLUSIONS

The acute ingestion of BRJ by hypertensive patients resulted in an improvement of endothelial function, which was associated with higher subendocardial viability and performance in myocardial contraction.

Dietary Inorganic Nitrate as an Ergogenic Aid: An Expert Consensus Derived via the Modified Delphi Technique

INTRODUCTION

Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be recommended as an ergogenic aid. Moreover, there is no consensus on the safe administration of dietary nitrate as an ergogenic aid. This study aimed to address these research gaps.

METHODS

The modified Delphi technique was used to establish the views of 12 expert panel members on the use of dietary nitrate as an ergogenic aid. Over three iterative rounds (two via questionnaire and one via videoconferencing), the expert panel members voted on 222 statements relating to dietary nitrate as an ergogenic aid. Consensus was reached when > 80% of the panel provided the same answer (i.e. yes or no). Statements for which > 80% of the panel cast a vote of insufficient evidence were categorised as such and removed from further voting. These statements were subsequently used to identify directions for future research.

RESULTS

The 12 panel members contributed to voting in all three rounds. A total of 39 statements (17.6%) reached consensus across the three rounds (20 yes, 19 no). In round one, 21 statements reached consensus (11 yes, 10 no). In round two, seven further statements reached consensus (4 yes, 3 no). In round three, an additional 11 statements reached consensus (5 yes, 6 no). The panel agreed that there was insufficient evidence for 134 (60.4%) of the statements, and were unable to agree on the outcome of the remaining statements.

CONCLUSIONS

This study provides information on the current expert consensus on dietary nitrate, which may be of value to athletes, coaches, practitioners and researchers. The effects of dietary nitrate appear to be diminished in individuals with a higher aerobic fitness (peak oxygen consumption [V̇O2peak] > 60 ml/kg/min), and therefore, aerobic fitness should be taken into account when considering use of dietary nitrate as an ergogenic aid. It is recommended that athletes looking to benefit from dietary nitrate supplementation should consume 8-16 mmol nitrate acutely or 4-16 mmol/day nitrate chronically (with the final dose ingested 2-4 h pre-exercise) to maximise ergogenic effects, taking into consideration that, from a safety perspective, athletes may be best advised to increase their intake of nitrate via vegetables and vegetable juices. Acute nitrate supplementation up to ~ 16 mmol is believed to be safe, although the safety of chronic nitrate supplementation requires further investigation. The expert panel agreed that there was insufficient evidence for most of the appraised statements, highlighting the need for future research in this area.

Bioactive Properties of Bread Formulated with Plant-based Functional Ingredients Before Consumption and Possible Links with Health Outcomes After Consumption- A Review

Bread is a commonly consumed staple and could be a viable medium to deliver plant-based ingredients that demonstrate health effects. This review brings together published evidence on the bioactive properties of bread formulated with plant-based ingredients. Health effects associated with the consumption of bread formulated with plant-based functional ingredients was also reviewed. Bioactive properties demonstrated by the functional ingredients fruits and vegetables, legumes, nuts and tea incorporated into bread include increased phenolic and polyphenolic content, increased antioxidant activity, and extension of bread shelf-life by impairment of lipid and protein oxidation. Acute health effects reported included appetite suppression, reduced diastolic blood pressure, improvements in glycaemia, insulinaemia and satiety effect. These metabolic effects are mainly short lived and not enough for a health claim. Longer term studies or comparison of those who consume and those who do not are needed. The incorporation of plant-based functional ingredients in bread could enhance the health-promoting effects of bread.

Therapeutic roles of plants for 15 hypothesised causal bases of Alzheimer's disease

Alzheimer's disease (AD) is progressive and ultimately fatal, with current drugs failing to reverse and cure it. This study aimed to find plant species which may provide therapeutic bioactivities targeted to causal agents proposed to be driving AD. A novel toolkit methodology was employed, whereby clinical symptoms were translated into categories recognized in ethnomedicine. These categories were applied to find plant species with therapeutic effects, mined from ethnomedical surveys. Survey locations were mapped to assess how this data is at risk. Bioactivities were found of therapeutic relevance to 15 hypothesised causal bases for AD. 107 species with an ethnological report of memory improvement demonstrated therapeutic activity for all these 15 causal bases. The majority of the surveys were found to reside within biodiversity hotspots (centres of high biodiversity under threat), with loss of traditional knowledge the most common threat. Our findings suggest that the documented plants provide a large resource of AD therapeutic potential. In demonstrating bioactivities targeted to these causal bases, such plants may have the capacity to reduce or reverse AD, with promise as drug leads to target multiple AD hallmarks. However, there is a need to preserve ethnomedical knowledge, and the habitats on which this knowledge depends.

A comprehensive review of beetroot (Beta vulgaris L.) bioactive components in the food and pharmaceutical industries

Beetroot is rich in various bioactive phytochemicals, which are beneficial for human health and exert protective effects against several disease conditions like cancer, atherosclerosis, etc. Beetroot has various therapeutic applications, including antioxidant, antibacterial, antiviral, and analgesic functions. Besides the pharmacological effects, food industries are trying to preserve beetroots or their phytochemicals using various food preservation methods, including drying and freezing, to preserve their antioxidant capacity. Beetroot is a functional food due to valuable active components such as minerals, amino acids, phenolic acid, flavonoid, betaxanthin, and betacyanin. Due to its stability, nontoxic and non-carcinogenic and nonpoisonous capabilities, beetroot has been used as an additive or preservative in food processing. Beetroot and its bioactive compounds are well reported to possess antioxidant, anti-inflammatory, antiapoptotic, antimicrobial, antiviral, etc. In this review, we provided updated details on (i) food processing, preservation and colorant methods using beetroot and its phytochemicals, (ii) synthesis and development of several nanoparticles using beetroot and its bioactive compounds against various diseases, (iii) the role of beetroot and its phytochemicals under disease conditions with molecular mechanisms. We have also discussed the role of other phytochemicals in beetroot and their health benefits. Recent technologies in food processing are also updated. We also addressed on molecular docking-assisted biological activity and screening for bioactive chemicals. Additionally, the role of betalain from different sources and its therapeutic effects have been listed. To the best of our knowledge, little or no work has been carried out on the impact of beetroot and its nanoformulation strategies for phytocompounds on antimicrobial, antiviral effects, etc. Moreover, epigenetic alterations caused by phytocompounds of beetroot under several diseases were not reported much. Thus, extensive research must be carried out to understand the molecular effects of beetroot in the near future.

Nitrate Derived From Beetroot Juice Lowers Blood Pressure in Patients With Arterial Hypertension: A Systematic Review and Meta-Analysis

Background

Although there are a considerable number of clinical studies on nitrate (NO3) rich beetroot juice (BRJ) and hypertension, it is difficult to indicate the real effects of NO3 from BRJ on the BP of hypertensive patients because there are still no estimates of the effects of NO3 derived from BRJ on the BP of hypertension patients.

Objective

To clarify these effects, we developed a systematic literature review with a meta-analysis of randomized clinical trials (RCTs).

Design

The searches were accomplished through EMBASE, Cochrane Library, MEDLINE, CINAHL, Web of Science, and LILACS databases. The study included single or double-blinded RCTs and participants older than 18 years with hypertension [systolic BP (SBP) > 130 mmHg and diastolic BP (DBP) > 80 mmHg]. NO3 BRJ was required to be consumed in a format that possibly blinded participants/researchers. These studies should also report the SBP and DBP values (mmHg) measured before and after the treatment. Risk of Bias tools and GRADE were enforced.

Results

Seven studies were included (218 participants). BRJ intervention time ranged from 3 to 60 days with daily dosages of 70-250 mL of BRJ. After the intervention with NO3 from BRJ, SBP underwent significant changes (p < 0.001) of -4.95 (95% CI: -8.88; -1.01) (GRADE: ⊕⊕⊕○ Moderate), but not for DBP (p = 0.06) -0.90 mmHg (95% CI: -3.16; 1.36) (GRADE: ⊕⊕⊕○ Moderate), compared to the control group.

Conclusions

The NO3 derived from BRJ reduces SBP, but not DBP in patients with arterial hypertension.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=269339.

Dietary nitrate intake and vegetable consumption, ambient particulate matter, and risk of hypertension in the Nurses' Health study

BACKGROUND

Studies have suggested that dietary nitrate could lower blood pressure levels whereas ambient particulate matter (PM) may increase risk of hypertension. However, it is unknown if these exposures may modify each other.

OBJECTIVES

We collected information on dietary nitrate intake and vegetables consumption and estimated long-term exposures to ambient PM for women in the Nurses' Health Study.

METHODS

Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for risk of hypertension were calculated using Cox proportional hazards models with adjustment for potential demographic, lifestyle and dietary confounders. Interactions were assessed with multiplicative interaction terms and stratified models.

RESULTS

Increases in dietary nitrate intake (per 150 mg/d) and green leafy vegetables consumption (per serving/day) were both significantly associated with decreases in hypertension risk (both multivariable-adjusted HRs were 0.97, 95% CI: 0.94, 0.99). Long-term exposure to ambient PM with an aerodynamic diameter ≤ 2.5 µm (PM_2.5) was associated with an increased risk of hypertension, with a multivariable-adjusted HR of hypertension of 1.06 (95% CI: 1.02, 1.11) per 10 µg/m³ increase in PM_2.5. Ambient PM_2.5 significantly modified the associations of dietary nitrate intake (P_interaction = 0.02) and green leafy vegetables consumption (P_interaction = 0.004). The associations with dietary factors were gradually weakened with increasing PM_2.5: the fully-adjusted HRs for risk of hypertension were 0.94 (95% CI: 0.89, 0.99) and 0.94 (95% CI: 0.90, 0.99) for per 150 mg/d increase in nitrate intake and per serving/d increase in green leafy vegetables consumption, respectively, in the lowest PM_2.5 quartile, and 1.00 (95% CI: 0.94, 1.06) and 1.02 (95% CI: 0.97, 1.08), respectively, in the highest PM_2.5 quartile.

CONCLUSION

Our research highlights a potentially protective effect of dietary nitrate intake in the prevention of hypertension and suggests that these benefits are attenuated by increasing exposure to ambient PM_2.5.

Feasibility and Acceptability of a Dietary Intervention to Reduce Salt Intake and Increase High-Nitrate Vegetable Consumption in Malaysian Middle-Aged and Older Adults with Elevated Blood Pressure: Findings from the DePEC-Nutrition Trial

The DePEC-Nutrition trial is a complex dietary and behavioural intervention of salt intake reduction combined with increased high-nitrate vegetable consumption among Malaysian middle-aged and older adults with elevated blood pressure. This study aimed to assess the feasibility and acceptability of the trial. Participants were recruited from the South East Asia Community Observatory (SEACO) database and randomised into one of four groups: (1) low salt; (2) high-nitrate vegetable; (3) combined high-nitrate vegetable and low salt; and (4) control. The intervention included a combination of group counselling sessions, information booklets, reinforcement videos and text messages to modify dietary behaviour. The primary outcomes evaluated were the measures of feasibility and acceptability of (1) recruitment, follow-up attendance and retention; (2) data collection procedures and clinical outcome measures; and (3) individual and combined multi-modal dietary interventions. A total of 74 participants were recruited, and the 10-month retention rate was 73%. Data collection procedures were acceptable with minimal missing data. All intervention strategies were feasible and acceptable, with group counselling being the most acceptable strategy. This study provides important insights into improving the screening process of participants, facilitating their access to the research facilities and refining the measurement protocols and dietary recommendations, which are instrumental in formulating the design of a full-scale definitive DePEC-Nutrition trial.

Mediterranean diet and cognitive function: From methodology to mechanisms of action

The traditional Mediterranean diet (MedDiet), rich in minimally processed plant foods and fish, has been widely recognized to be one of the healthiest diets. Data from multiple randomized clinical trials have demonstrated its powerful effect against oxidative stress, inflammation and the development and progression of cardiovascular disease, type 2 diabetes, and other metabolic conditions that play a crucial role in the pathogenesis of neurodegenerative diseases. The protecting effects of the MedDiet against cognitive decline have been investigated in several observational and experimental studies. Data from observational studies suggest that the MedDiet may represent an effective dietary strategy for the early prevention of dementia, although these findings require further substantiation in clinical trials which have so far produced inconclusive results. Moreover, as we discuss in this review, accumulating data emphasizes the importance of: 1) maintaining an optimal nutritional and metabolic status for the promotion of healthy cognitive aging, and 2) implementing cognition-sparing dietary and lifestyle interventions during early time-sensitive windows before the pathological cascades turn into an irreversible state. In summary, components of the MedDiet pattern, such as essential fatty acids, polyphenols and vitamins, have been associated with reduced oxidative stress and the current evidence from observational studies seems to assign to the MedDiet a beneficial role in promoting brain health; however, results from clinical trials have been inconsistent. While we advocate for longitudinal analyses and for larger and longer clinical trials to be conducted, we assert our interim support to the use of the MedDiet as a protective dietary intervention for cognitive function based on its proven cardiovascular and metabolic benefits.

Endogenous Hemoprotein-Dependent Signaling Pathways of Nitric Oxide and Nitrite

Interdisciplinary research at the interface of chemistry, physiology, and biomedicine have uncovered pivotal roles of nitric oxide (NO) as a signaling molecule that regulates vascular tone, platelet aggregation, and other pathways relevant to human health and disease. Heme is central to physiological NO signaling, serving as the active site for canonical NO biosynthesis in nitric oxide synthase (NOS) enzymes and as the highly selective NO binding site in the soluble guanylyl cyclase receptor. Outside of the primary NOS-dependent biosynthetic pathway, other hemoproteins, including hemoglobin and myoglobin, generate NO via the reduction of nitrite. This auxiliary hemoprotein reaction unlocks a "second axis" of NO signaling in which nitrite serves as a stable NO reservoir. In this Forum Article, we highlight these NO-dependent physiological pathways and examine complex chemical and biochemical reactions that govern NO and nitrite signaling in vivo. We focus on hemoprotein-dependent reaction pathways that generate and consume NO in the presence of nitrite and consider intermediate nitrogen oxides, including NO2, N2O3, and S-nitrosothiols, that may facilitate nitrite-based signaling in blood vessels and tissues. We also discuss emergent therapeutic strategies that leverage our understanding of these key reaction pathways to target NO signaling and treat a wide range of diseases.

The effect of beetroot inorganic nitrate supplementation on cardiovascular risk factors: A systematic review and meta-regression of randomized controlled trials

OBJECTIVES

Inorganic nitrate is one of the most effective compounds in beetroot for improving cardiovascular function due to its conversion to nitric oxide in the body. This review and meta-analysis aimed to investigate the role of beetroot inorganic nitrate supplementation on adults' cardiovascular risk factors.

METHODS

We conducted a systematic literature review of articles published without time limitation until November 2020 in PubMed, Embase, ISI Web of Science, Scopus, Cochrane Library, and gray literature databases. We included the original randomized clinical trials (RCTs) in which the effect of beetroot inorganic nitrate supplementation on endothelial function, arterial stiffness, and blood pressure was studied.

RESULTS

43 studies were included for qualitative synthesis, out of which 27 were eligible for meta-analysis. Beetroot inorganic nitrate supplementation significantly decreased Arterial Stiffness (Pulse Wave Velocity (-0.27 m/s, p = 0.04)) and increased Endothelial function (Flow Mediated Dilation: 0.62%, p = 0.002) but did not change other parameters (p > 0.05).

CONCLUSION

Beetroot inorganic nitrate supplementation might have a beneficial effect on cardiovascular risk factors. Further high-quality investigations will be needed to provide sufficient evidence.

Dietary nitrate and population health: a narrative review of the translational potential of existing laboratory studies

BACKGROUND

Dietary inorganic nitrate (NO3-) is a polyatomic ion, which is present in large quantities in green leafy vegetables and beetroot, and has attracted considerable attention in recent years as a potential health-promoting dietary compound. Numerous small, well-controlled laboratory studies have reported beneficial health effects of inorganic NO3- consumption on blood pressure, endothelial function, cerebrovascular blood flow, cognitive function, and exercise performance. Translating the findings from small laboratory studies into 'real-world' applications requires careful consideration.

MAIN BODY

This article provides a brief overview of the existing empirical evidence basis for the purported health-promoting effects of dietary NO3- consumption. Key areas for future research are then proposed to evaluate whether promising findings observed in small animal and human laboratory studies can effectively translate into clinically relevant improvements in population health. These proposals include: 1) conducting large-scale, longer duration trials with hard clinical endpoints (e.g. cardiovascular disease incidence); 2) exploring the feasibility and acceptability of different strategies to facilitate a prolonged increase in dietary NO3- intake; 3) exploitation of existing cohort studies to explore associations between NO3- intake and health outcomes, a research approach allowing larger samples sizes and longer duration follow up than is feasible in randomised controlled trials; 4) identifying factors which might account for individual differences in the response to inorganic NO3- (e.g. sex, genetics, habitual diet) and could assist with targeted/personalised nutritional interventions; 5) exploring the influence of oral health and medication on the therapeutic potential of NO3- supplementation; and 6) examining potential risk of adverse events with long term high- NO3- diets.

CONCLUSION

The salutary effects of dietary NO3- are well established in small, well-controlled laboratory studies. Much less is known about the feasibility and efficacy of long-term dietary NO3- enrichment for promoting health, and the factors which might explain the variable responsiveness to dietary NO3- supplementation between individuals. Future research focussing on the translation of laboratory data will provide valuable insight into the potential applications of dietary NO3- supplementation to improve population health.

Effects of a Mediterranean diet on blood pressure: a systematic review and meta-analysis of randomized controlled trials and observational studies

OBJECTIVE

To conduct a systematic review and meta-analysis investigating effects of MedDiet on blood pressure in randomized controlled trials (RCTs) and associations of MedDiet with risk of hypertension in observational studies.

METHODS

PubMed, The Cochrane Library and EBSCOhost were searched from inception until January 2020 for studies that met the following criteria: participants aged at least 18 years, RCTs investigating effects of a MedDiet versus control on BP, observational studies exploring associations between MedDiet adherence and risk of hypertension. Random-effects meta-analyses were conducted. Meta-regression and subgroup analyses were performed for RCTs to identify potential effect moderators.

RESULTS

Nineteen RCTs reporting data on 4137 participants and 16 observational studies reporting data on 59 001 participants were included in the meta-analysis. MedDiet interventions reduced SBP and DBP by a mean -1.4 mmHg (95% CI: -2.40 to -0.39 mmHg, P = 0.007, I2 = 53.5%, Q = 44.7, τ2 = 1.65, df = 19) and -1.5 mmHg (95% CI: -2.74 to -0.32 mmHg, P = 0.013, I2 = 71.5%, Q = 51.6, τ2 = 4.72, df = 19) versus control, respectively. Meta-regression revealed that longer study duration and higher baseline SBP was associated with a greater decrease in BP, in response to a MedDiet (P < 0.05). In observational studies, odds of developing hypertension were 13% lower with higher versus lower MedDiet adherence (95% CI: 0.78--0.98, P = 0.017, I2 = 69.6%, Q = 41.1, τ2 = 0.03, df = 17).

CONCLUSION

Data suggest that MedDiet is an effective dietary strategy to aid BP control, which may contribute towards the lower risk of CVD reported with this dietary pattern. This study was registered with PROSPERO: CRD42019125073.

Beetroot as a Potential Functional Food for Cancer Chemoprevention, a Narrative Review

Patients with cancer are prone to several debilitating side effects including fatigue, insomnia, depression and cognitive disturbances. Beetroot (Beta vulgaris L.) as a health promoting functional food may be potentially beneficial in cancer. As a source of polyphenols, flavonoids, dietary nitrates and other useful nutrients, beetroot supplementation may provide a holistic means to prevent cancer and manage undesired effects associated with chemotherapy. The main aim of this narrative review is to discuss beetroot's nutrient composition, current studies on its potential utility in chemoprevention and cancer-related fatigue or treatment-related side effects such as cardiotoxicity. This review aims to provide the current status of knowledge and to identify the related research gaps in this area. The flavonoids and polyphenolic components present in abundance in beetroot support its significant antioxidant and anti-inflammatory capacities. Most in vitro and in vivo studies have shown promising results; however, the molecular mechanisms underlying chemopreventive and chemoprotective effects of beetroot have not been completely elucidated. Although recent clinical trials have shown that beetroot supplementation improves human performance, translational studies on beetroot and its functional benefits in managing fatigue or other symptoms in patients with cancer are still lacking.

A high methionine and low folate diet alters glucose homeostasis and gut microbiome

Hyperhomocysteinemia (HHcy) is considered as a risk factor for several complications, including cardiovascular and neurological disorders. A high methionine low folate (HMLF) diet chronically causes HHcy by accumulating homocysteine in the systemic circulation. Elevated Hcy level is also associated with the incidence of diabetes mellitus. However, very few studies focus on the impact of HMLF diet on glucose homeostasis, and that on gut microbiome profile. HHcy was induced by feeding C57BL/6 mice a HMLF diet for 8 weeks. The HMLF diet feeding resulted in a progressive body weight loss, and development of slight glucose intolerance and insulin resistance in HHcy mice. Notably, the HMLF diet alters the gut microbiome profile and increases the relative abundance of porphyromonadaceae family of bacteria in HHcy mice. These findings provide new insights into the roles of dysregulated glucose homeostasis and gut flora in the pathogenesis of HHcy-related complications.

Renovascular effects of inorganic nitrate following ischemia-reperfusion of the kidney

BACKGROUND

Renal ischemia-reperfusion (IR) injury is a common cause of acute kidney injury (AKI), which is associated with oxidative stress and reduced nitric oxide (NO) bioactivity and increased risk of developing chronic kidney disease (CKD) and cardiovascular disease (CVD). New strategies that restore redox balance may have therapeutic implications during AKI and associated complications.

AIM

To investigate the therapeutic value of boosting the nitrate-nitrite-NO pathway during development of IR-induced renal and cardiovascular dysfunction.

METHODS

Male C57BL/6 J mice were given sodium nitrate (10 mg/kg, i. p) or vehicle 2 h prior to warm ischemia of the left kidney (45 min) followed by sodium nitrate supplementation in the drinking water (1 mmol/kg/day) for the following 2 weeks. Blood pressure and glomerular filtration rate were measured and blood and kidneys were collected and used for biochemical and histological analyses as well as renal vessel reactivity studies. Glomerular endothelial cells exposed to hypoxia-reoxygenation, with or without angiotensin II, were used for mechanistic studies.

RESULTS

IR was associated with reduced renal function and slightly elevated blood pressure, in combination with renal injuries, inflammation, endothelial dysfunction, increased Ang II levels and Ang II-mediated vasoreactivity, which were all ameliorated by nitrate. Moreover, treatment with nitrate (in vivo) and nitrite (in vitro) restored NO bioactivity and reduced mitochondrial oxidative stress and injuries.

CONCLUSIONS

Acute treatment with inorganic nitrate prior to renal ischemia may serve as a novel therapeutic approach to prevent AKI and CKD and associated risk of developing cardiovascular dysfunction.