Dietary nitrate provides sustained blood pressure lowering in hypertensive patients: a randomized, phase 2, double-blind, placebo-controlled study

Angina pectoris worsened by mouthwash

We report a case of variant (Prinzmetal's) angina pectoris in a 51-year-old man in whom coronary angiography revealed sluggish flow of contrast material. His chest pain was not controlled with standard antianginal therapy, but it resolved after discontinuation of mouthwash. This is the first case of angina pectoris reported that vastly improved after discontinuation of mouthwash.

Acute Supplementation with Nitrate-Rich Beetroot Juice Causes a Greater Increase in Plasma Nitrite and Reduction in Blood Pressure of Older Compared to Younger Adults

Nitrate-rich beetroot juice supplementation has been shown to improve cardiovascular and cognitive function in younger and older adults via increased nitric oxide production. However, it is unclear whether the level of effects differs between the two groups. We hypothesized that acute supplementation with nitrate-rich beetroot juice would improve cardiovascular and cognitive function in older and younger adults, with the potential for greater improvements in older adults. Thirteen younger (18–30 years) and 11 older (50–70 years) adults consumed either 150 mL of nitrate-rich beetroot juice (BR; 10.5 mmol nitrate) or placebo (PL; 1 mmol nitrate) in a double-blind, crossover design, 2.25 h prior to a 30-min treadmill walk. Plasma nitrate and nitrite concentrations, blood pressure (BP), heart rate (HR), cognitive function, mood and perceptual tests were performed throughout the trial. BR consumption significantly increased plasma nitrate (p < 0.001) and nitrite (p = 0.003) concentrations and reduced systolic BP (p < 0.001) in both age groups and reduced diastolic BP (p = 0.013) in older adults. Older adults showed a greater elevation in plasma nitrite (p = 0.038) and a greater reduction in diastolic BP (p = 0.005) following BR consumption than younger adults. Reaction time was improved in the Stroop test following BR supplementation for both groups (p = 0.045). Acute BR supplementation increased plasma nitrite concentrations and reduced diastolic BP to a greater degree in older adults; whilst systolic BP was reduced in both older and younger adults, suggesting nitrate-rich BR may improve cardiovascular health, particularly in older adults due to the greater benefits from reductions in diastolic BP.

Acute Supplementation with Nitrate-Rich Beetroot Juice Causes a Greater Increase in Plasma Nitrite and Reduction in Blood Pressure of Older Compared to Younger Adults

Nitrate-rich beetroot juice supplementation has been shown to improve cardiovascular and cognitive function in younger and older adults via increased nitric oxide production. However, it is unclear whether the level of effects differs between the two groups. We hypothesized that acute supplementation with nitrate-rich beetroot juice would improve cardiovascular and cognitive function in older and younger adults, with the potential for greater improvements in older adults. Thirteen younger (18-30 years) and 11 older (50-70 years) adults consumed either 150 mL of nitrate-rich beetroot juice (BR; 10.5 mmol nitrate) or placebo (PL; 1 mmol nitrate) in a double-blind, crossover design, 2.25 h prior to a 30-min treadmill walk. Plasma nitrate and nitrite concentrations, blood pressure (BP), heart rate (HR), cognitive function, mood and perceptual tests were performed throughout the trial. BR consumption significantly increased plasma nitrate (p < 0.001) and nitrite (p = 0.003) concentrations and reduced systolic BP (p < 0.001) in both age groups and reduced diastolic BP (p = 0.013) in older adults. Older adults showed a greater elevation in plasma nitrite (p = 0.038) and a greater reduction in diastolic BP (p = 0.005) following BR consumption than younger adults. Reaction time was improved in the Stroop test following BR supplementation for both groups (p = 0.045). Acute BR supplementation increased plasma nitrite concentrations and reduced diastolic BP to a greater degree in older adults; whilst systolic BP was reduced in both older and younger adults, suggesting nitrate-rich BR may improve cardiovascular health, particularly in older adults due to the greater benefits from reductions in diastolic BP.

Dietary nitrate supplementation enhances cerebrovascular CO2 reactivity in a sex-specific manner

Insufficient nitric oxide (NO) bioavailability plays an important role in endothelial dysfunction, and increased NO has the potential to enhance cerebral blood flow (CBF). Dietary supplementation with sodium nitrate, a precursor of NO, could improve cerebrovascular function, but this has not been investigated. In 17 individuals, we examined the effects of a 7-day supplementation of dietary nitrate (0.1 mmol·kg^-1·day ^-1) on cerebrovascular function using a randomized, single-blinded placebo-controlled crossover design. We hypothesized that 7-day dietary nitrate supplementation increases CBF response to CO₂ (cerebrovascular CO₂ reactivity) and cerebral autoregulation (CA). We assessed middle cerebral artery blood velocity (MCAv) and blood pressure (BP) at rest and during CO₂ breathing. Transfer function analysis was performed on resting beat-to-beat MCAv and BP to determine CA, from which phase, gain, and coherence of the BP-MCAv data were derived. Dietary nitrate elevated plasma nitrate concentration by ~420% (P < 0.001) and lowered gain (d = 1.2, P = 0.025) and phase of the BP-MCAv signal compared with placebo treatment (d = 0.7, P = 0.043), while coherence was unaffected (P = 0.122). Dietary nitrate increased the MCAv-CO₂ slope in a sex-specific manner (interaction: P = 0.016). Dietary nitrate increased the MCAv-CO₂ slope in men (d = 1.0, P = 0.014 vs. placebo), but had no effect in women (P = 0.919). Our data demonstrate that dietary nitrate greatly increased cerebrovascular CO₂ reactivity in healthy individuals, while its effect on CA remains unclear. The selective increase in the MCAv-CO₂ slope observed in men indicates a clear sexual dimorphic role of NO in cerebrovascular function.NEW & NOTEWORTHY We found dietary nitrate supplementation improved the brain blood vessels' response to CO₂, cerebrovascular CO₂ reactivity, without affecting blood pressure in a group of healthy individuals. Meanwhile, the effect of dietary nitrate on the relationship between blood pressure and brain blood flow, cerebral autoregulation, was inconclusive. The improvement in cerebrovascular CO₂ reactivity was only observed in the male participants, alluding to a sex difference in the effect of dietary nitrate on brain blood flow control. Our findings indicate that dietary nitrate could be an effective strategy to enhance cerebrovascular CO₂ reactivity.

Dietary intake of inorganic nitrate in vegetarians and omnivores and its impact on blood pressure, resting metabolic rate and the oral microbiome

Vegetarian diets are commonly associated with lower blood pressure levels. This has been related to greater consumption of inorganic nitrate, since vegetables are the main source of this anion. Dietary nitrate is reduced to nitrite by commensal bacteria in the mouth, which in turn leads to increased circulatory nitrite availability. Nitrite can form nitric oxide by several pathways promoting a reduction in the vascular tone and lower blood pressure. This study tested whether vegetarians have higher concentrations of nitrite in saliva and plasma, and lower blood pressure and resting metabolic rate (RMR), due to higher intakes of nitrate, compared to omnivores. Following a non-randomized, cross-over and single-blinded design we measured dietary nitrate intake, blood pressure and RMR in young and healthy vegetarians (n = 22) and omnivores (n = 19) with similar characteristics after using placebo or antibacterial mouthwash for a week to inhibit oral bacteria. Additionally, we analyzed salivary and plasma nitrate and nitrite concentrations, as well as the oral nitrate-reduction rate and oral microbiome in both groups. Dietary nitrate intake in vegetarians (97 ± 79 mg/day) was not statistically different (P > 0.05) to omnivores (78 ± 47 mg/day). Salivary and plasma nitrate and nitrite concentrations were similar after placebo mouthwash in both groups (P > 0.05). The oral nitrate-reducing capacity, abundance of oral bacterial species, blood pressure and RMR were also similar between vegetarians and omnivores (P > 0.05). Antibacterial mouthwash significantly decreased abundance of oral nitrate-reducing bacterial species in vegetarians (^_16.9%; P < 0.001) and omnivores (^_17.4%; P < 0.001), which in turn led to a significant reduction of the oral nitrate-reducing capacity in vegetarians (-78%; P < 0.001) and omnivores (-85%; P < 0.001). However, this did not lead to a significant increase in blood pressure and RMR in either groups (P > 0.05). These findings suggest that vegetarian diets may not alter nitrate and nitrite homeostasis, or the oral microbiome, compared to an omnivore diet. Additionally, inhibition of oral nitrite synthesis for a week with antibacterial mouthwash did not cause a significant raise in blood pressure and RMR in healthy, young individuals independent of diet.

Consumption of Aged White Wine under a Veil of Flor Reduces Blood Pressure-Increasing Plasma Nitric Oxide in Men at High Cardiovascular Risk

Background: Hypertension remains the largest attributable risk factor of cardiovascular disease (CVD), and a reduction of cardiovascular events is linked to diminished elevated blood pressure (BP) values. High alcohol intake is a common cause of hypertension, but some studies have suggested that moderate wine consumption may reduce BP and increase plasma nitric oxide (NO) due to its polyphenol content. Objective: The aim of the present study was to compare the effects of Andalusian aged white wine (AWW) under a veil of flor, an alcoholic beverage with a moderate polyphenol content, with those of gin, an alcoholic beverage without polyphenols, on BP and plasma NO in men at high cardiovascular risk. Methods: This study was designed as an open, randomized crossover-controlled trial in which 38 high-risk male volunteers, aged 55 to 80, received 30 g of ethanol daily in the form of AWW or gin. This was carried out over the course of three weeks, after a two-week washout period. At baseline and after each intervention period, BP, anthropometric parameters, and plasma NO were measured; food intake was also recorded, and physical activity was monitored. Results: Compared to gin, AWW significantly reduced systolic and diastolic BP (p ≤ 0.033; both) and increased plasma NO levels (p = 0.013). Additionally, changes in BP values observed after AWW significantly correlated with increases in plasma NO. No changes in food intake, physical activity, body weight, or waist were observed between the two intervention periods. Conclusions: Moderate daily consumption of AWW may be useful to reduce elevated BP due to an increase of NO synthesis. This effect could be attributed to grape-derived compounds in AWW, such as polyphenols, which are not present in gin.

Acute interaction between oral glucose (75 g as Lucozade) and inorganic nitrate: Decreased insulin clearance, but lack of blood pressure-lowering

AIMS

Dietary inorganic nitrate (NO₃ ^- ) lowers peripheral blood pressure (BP) in healthy volunteers, but lacks such effect in individuals with, or at risk of, type 2 diabetes mellitus (T2DM). Whilst this is commonly assumed to be a consequence of chronic hyperglycaemia/hyperinsulinaemia, we hypothesized that acute physiological elevations in plasma [glucose]/[insulin] blunt the haemodynamic responses to NO₃ ^- , a pertinent question for carbohydrate-rich Western diets.

METHODS

We conducted an acute, randomized, placebo-controlled, double-blind, crossover study on the haemodynamic and metabolic effects of potassium nitrate (8 or 24 mmol KNO₃ ) vs. potassium chloride (KCl; placebo) administered 1 hour prior to an oral glucose tolerance test in 33 healthy volunteers.

RESULTS

Compared to placebo, there were no significant differences in systolic or diastolic BP (P = 0.27 and P = 0.30 on ANOVA, respectively) with KNO₃ , nor in pulse wave velocity or central systolic BP (P = 0.99 and P = 0.54 on ANOVA, respectively). Whilst there were significant elevations from baseline for plasma [glucose] and [C-peptide], no differences between interventions were observed. A significant increase in plasma [insulin] was observed with KNO₃ vs. KCl (n = 33; P = 0.014 on ANOVA) with the effect driven by the high-dose cohort (24 mmol, n = 13; P < 0.001 on ANOVA; at T = 0.75 h mean difference 210.4 pmol/L (95% CI 28.5 to 392.3), P = 0.012).

CONCLUSIONS

In healthy adults, acute physiological elevations of plasma [glucose] and [insulin] result in a lack of BP-lowering with dietary nitrate. The increase in plasma [insulin] without a corresponding change in [C-peptide] or [glucose] suggests that high-dose NO₃ ^- decreases insulin clearance. A likely mechanism is via NO-dependent inhibition of insulin-degrading enzyme.

Small Amounts of Inorganic Nitrate or Beetroot Provide Substantial Protection From Salt-Induced Increases in Blood Pressure

To reduce the risk of salt-induced hypertension, medical authorities have emphasized dietary guidelines promoting high intakes of potassium and low intakes of salt that provide molar ratios of potassium to salt of ≥1:1. However, during the past several decades, relatively few people have changed their eating habits sufficiently to reach the recommended dietary goals for salt and potassium. Thus, new strategies that reduce the risk of salt-induced hypertension without requiring major changes in dietary habits would be of considerable medical interest. In the current studies in a widely used model of salt-induced hypertension, the Dahl salt-sensitive rat, we found that supplemental dietary sodium nitrate confers substantial protection from initiation of salt-induced hypertension when the molar ratio of added nitrate to added salt is only ≈1:170. Provision of a low molar ratio of added nitrate to added salt of ≈1:110 by supplementing the diet with beetroot also conferred substantial protection against salt-induced increases in blood pressure. The results suggest that on a molar basis and a weight basis, dietary nitrate may be ≈100× more potent than dietary potassium with respect to providing substantial resistance to the pressor effects of increased salt intake. Given that leafy green and root vegetables contain large amounts of inorganic nitrate, these findings raise the possibility that fortification of salty food products with small amounts of a nitrate-rich vegetable concentrate may provide a simple method for reducing risk for salt-induced hypertension.

Acute Dietary Nitrate Supplementation Improves Flow Mediated Dilatation of the Superficial Femoral Artery in Healthy Older Males

Aging is often associated with reduced leg blood flow, increased arterial stiffness, and endothelial dysfunction, all of which are related to declining nitric oxide (NO) bioavailability. Flow mediated dilatation (FMD) and passive leg movement (PLM) hyperaemia are two techniques used to measure NO-dependent vascular function. We hypothesised that acute dietary nitrate (NO3-) supplementation would improve NO bioavailability, leg FMD, and PLM hyperaemia. Fifteen healthy older men (69 ± 4 years) attended two experiment sessions and consumed either 140 mL of concentrated beetroot juice (800 mg NO3-) or placebo (NO3--depleted beetroot juice) in a randomised, double blind, cross-over design study. Plasma nitrite (NO2-) and NO3-, blood pressure (BP), augmentation index (AIx75), pulse wave velocity (PWV), FMD of the superficial femoral artery, and PLM hyperaemia were measured immediately before and 2.5 h after consuming NO3- and placebo. Placebo had no effect but NO3- led to an 8.6-fold increase in plasma NO2-, which was accompanied by an increase in FMD (NO3-: +1.18 ± 0.94% vs. placebo: 0.23 ± 1.13%, p = 0.002), and a reduction in AIx75 (NO3-: -8.7 ± 11.6% vs. placebo: -4.6 ± 5.5%, p = 0.027). PLM hyperaemia, BP, and PWV were unchanged during both trials. This study showed that a dose of dietary NO3- improved NO bioavailability and enhanced endothelial function as measured by femoral artery FMD. These findings provide insight into the specific central and peripheral vascular responses to dietary NO3- supplementation in older adults.

Dietary nitrate consumption and risk of CHD in women from the Nurses' Health Study

The consumption of nitrate-rich vegetables can acutely lower blood pressure and improve mediators shown to optimise vascular health. However, we do not yet understand the impact of long-term habitual dietary nitrate intake and its association with CVD. Therefore, the aim of this investigation was to examine the relationship between habitual dietary nitrate intakes and risk of CHD in women from the Nurses' Health Study. We prospectively followed 62 535 women who were free from diabetes, CVD and cancer at baseline in 1986. Information on diet was updated every 4 years with validated FFQ. The main outcome was CHD defined by the occurrence of non-fatal myocardial infarction or fatal CHD. Cox proportional hazard regression models were used to estimate the relative risks (RR) and 95 % CI. During 26 years of follow-up, 2257 cases of CHD were identified. When comparing the highest quintile of nitrate intake with the lowest quintile, in aged-adjusted analysis there was a protective association for CHD (RR=0·77, 95 % CI 0·68, 0·97; P=0·0002) which dissipated after further adjustment for smoking, physical activity, BMI and race (RR=0·91; 95 % CI 0·80, 1·04; P=0·27). This magnitude of association was further attenuated once we adjusted for the Alternative Healthy Eating Index excluding vegetable and fruit consumption (RR=1·04, 95 % CI 0·91, 1·20; P=0·34). Dietary nitrate intake was not related to the risk of CHD after adjustment for other lifestyle and non-vegetable dietary factors in a large group of US women.

A Double-Blind Placebo-Controlled Crossover Study of the Effect of Beetroot Juice Containing Dietary Nitrate on Aortic and Brachial Blood Pressure Over 24 h

Dietary inorganic nitrate in beetroot can act as a source of nitric oxide and has been reported to lower brachial blood pressure (BP). This study examined the effect of inorganic nitrate in beetroot juice on aortic (central) BP acutely and over the subsequent 24-h period. A double blind, randomized, placebo-controlled crossover trial was performed in fifteen healthy, normotensive men and women (age 22–40 years). Participants were randomized to receive beetroot juice containing nitrate (6.5–7.3 mmol) or placebo beetroot juice from which nitrate had been removed (<0.06 mmol nitrate). Effects on aortic systolic BP were measured at 30 min (primary endpoint), 60 min and over a subsequent 24 h period using an ambulatory BP monitor. Carotid-femoral pulse wave velocity (cfPWV) was also measured at 30 min. Following a washout period, the procedure was repeated within 7 days with crossover to the opposite arm of the trial. Compared with placebo, ingestion of beetroot juice containing nitrate lowered aortic systolic BP at 30 min by 5.2 (1.9–8.5) mmHg [mean (95% confidence interval); p < 0.01]. A smaller effect on aortic systolic BP was observed at 60 min. There were minimal effects on brachial BP or cfPWV. Effects on aortic systolic BP were not sustained over the subsequent 24 h and there were no effects on other hemodynamic parameters during ambulatory monitoring. A single dose of beetroot juice containing nitrate lowers aortic BP more effectively than brachial BP in the short term, but the effects are comparatively short-lived and do not persist over the course of the same day.

Mechanisms impairing blood pressure responses to nitrite and nitrate

Hypertension is a multifactorial disease associated with impaired nitric oxide (NO) production and bioavailability. In this respect, restoring NO activity by using nitrite and nitrate has been considered a potential therapeutic strategy to treat hypertension. This possibility is justified by the understanding that both nitrite and nitrate may be recycled back to NO and also promote the generation of other bioactive species. This process involves a complex biological circuit known as the enterosalivary cycle of nitrate, where this anion is actively taken up by the salivary glands and converted to nitrite by nitrate-reducing bacteria in the oral cavity. Nitrite is then ingested and reduced to NO and other nitroso species under the acid conditions of the stomach, whereas reminiscent nitrite that escapes gastric reduction is absorbed systemically and can be converted into NO by nitrite-reductases in tissues. While there is no doubt that nitrite and nitrate exert antihypertensive effects, several agents can impair the blood pressure responses to these anions by disrupting the enterosalivary cycle of nitrate. These agents include dietary and smoking-derived thiocyanate, antiseptic mouthwash, proton pump inhibitors, ascorbate at high concentrations, and xanthine oxidoreductase inhibitors. In this article, we provide an overview of the physiological aspects of nitrite and nitrate bioactivation and the therapeutic potential of these anions in hypertension. We also discuss mechanisms by which agents counteracting the antihypertensive responses to nitrite and nitrate mediate their effects. These critical aspects should be taken into consideration when suggesting nitrate or nitrite-based therapies to patients.

Beetroot juice supplementation for the prevention of cold symptoms associated with stress: A proof-of-concept study

OBJECTIVES

Psychological stress has been linked to common cold symptoms. Nitric oxide (NO) is part of the first line of epithelial defense against pathogens, and beetroot juice is a source of dietary nitrate that increases NO availability. We therefore tested whether beetroot juice protects against cold symptoms in a period of sustained acute stress.

DESIGN

Seventy-six students, 16 of these with asthma, were randomly assigned to seven daily doses of beetroot juice or no supplementation control during their final exams.

METHODS

Participants completed stress ratings, a cold symptom questionnaire, and exhaled NO measurements at a low-stress period and two periods during their final exams, with one questionnaire follow-up assessment seven days after finals.

RESULTS

Beetroot juice was associated with reduced symptoms of cold and sickness during and following finals. Those with asthma showed the greatest benefits. Higher exhaled NO was concurrently and prospectively associated with reduced symptomatology.

CONCLUSION

Beetroot juice during periods of psychological stress protects against cold symptoms. Preliminary evidence suggests particular benefits in asthma, which could translate into reduced asthma exacerbations due to respiratory infections. Clinical Trial ID: NCT03159273.

Effects of acute dietary nitrate supplementation on aortic blood pressures and pulse wave characteristics in post-menopausal women

PURPOSE

Consumption of nitrate-rich beetroot juice can lower blood pressure in peripheral as well as central arteries and may exert additional hemodynamic benefits (e.g. reduced aortic wave reflections). The specific influence of nitrate supplementation on arterial pressures and aortic wave properties in postmenopausal women, a group that experiences accelerated increases in these variables with age, is unknown. Accordingly, the primary aim of this study was to determine the effect of consuming nitrate-rich beetroot juice on resting brachial and aortic blood pressures (BP) and pulse wave characteristics in a group of healthy postmenopausal women, in comparison to a true (nitrate-free beetroot juice) placebo.

METHODS

Brachial (oscillometric cuff) and radial (SphygmoCor) pressures and derived-aortic waveforms were measured during supine rest in thirteen healthy postmenopausal women (63 ± 1 yr) before and 100 min after consumption of 140 ml of either nitrate-rich (9.7 mmol, 0.6 gm NO₃^-) or nitrate-depleted beetroot juice on randomized visits approximately 10 days apart (cross-over design). Ten young premenopausal women (22 ± 1 yr) served as a reference (non-supplemented) cohort.

RESULTS

Brachial and derived-aortic variables showed the expected age-associated differences in these women (all p < 0.05). In post-menopausal women, nitrate supplementation reduced (p < 0.05 vs. placebo visit) brachial systolic BP (BR_nitrate -4.9 ± 2.1 mmHg vs BR_placebo +1.1 ± 1.8 mmHg), brachial mean BP (BR_nitrate -4.1 ± 1.7 mmHg vs BR_placebo +0.9 ± 1.3 mmHg), aortic systolic BP (BR_nitrate -6.3 ± 2.0 mmHg vs BR_placebo +0.5 ± 1.7 mmHg) and aortic mean BP (BR_nitrate -4.1 ± 1.7 mmHg vs BR_placebo +0.9 ± 1.3 mmHg), and increased pulse pressure amplification (BR_nitrate +4.6 ± 2.0% vs BR_placebo +0.7 ± 2.5%, p = 0.04), but did not alter aortic pulse wave velocity or any other derived-aortic variables (e.g., augmentation pressure or index).

CONCLUSIONS

Dietary nitrate supplementation favorably modifies aortic systolic and mean blood pressure under resting conditions in healthy postmenopausal women. Acute supplementation of nitrate does not, however, appear to restore indices of aortic stiffness in this group. Future work should evaluate chronic, long-term effects of this non-pharmacological supplement.

Association of Periodontal Disease and Edentulism With Hypertension Risk in Postmenopausal Women

BACKGROUND

Multiple cross-sectional epidemiologic studies have suggested an association between periodontal disease and tooth loss and hypertension, but the temporality of these associations remains unclear. The objective of our study was to evaluate the association of baseline self-reported periodontal disease and edentulism with incident hypertension.

METHODS

Study participants were 36,692 postmenopausal women in the Women's Health Initiative-Observational Study who were followed annually from initial periodontal assessment (1998-2003) through 2015 (mean follow-up 8.3 years) for newly diagnosed treated hypertension. Cox proportional hazards regression with adjustment for potential confounders was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Edentulism was significantly associated with incident hypertension in crude (HR (95% CI) = 1.38 (1.28-1.49)) and adjusted (HR (95% CI) = 1.21 (1.11-1.30)) models. This association was stronger among those <60 years compared to ≥60 years (P interaction 0.04) and among those with <120 mm Hg systolic blood pressure, compared to those with ≥120 mm Hg (P interaction 0.004). No association was found between periodontal disease and hypertension.

CONCLUSIONS

These findings suggest that edentulous postmenopausal women may represent a group with higher risk of developing future hypertension. As such improved dental hygiene among those at risk for tooth loss as well as preventive measures among the edentulous such as closer blood pressure monitoring, dietary modification, physical activity, and weight loss may be warranted to reduce disease burden of hypertension. Further studies are needed to clarify these results and further elucidate a potential role of periodontal conditions on hypertension risk.

Augmentation of Whole-Body Metabolic Status by Mind-Body Training: Synchronous Integration of Tissue- and Organ-Specific Mitochondrial Function

The objective of our concise review is to elaborate an evidence-based integrative medicine model that incorporates functional linkages of key aspects of cortically-driven mind-body training procedures to biochemical and molecular processes driving enhanced cellular bioenergetics and whole-body metabolic advantage. This entails the adoption of a unified biological systems approach to selectively elucidate basic biochemical and molecular events responsible for achieving physiological relaxation of complex cellular structures. We provide accumulated evidence in support of the potential synergy of voluntary breathing exercises in combination with meditation and/or complementary cognitive tasks to promote medically beneficial enhancements in whole-body relaxation, anti-stress mechanisms, and restorative sleep. Accordingly, we propose that the widespread metabolic and physiological advantages emanating from a sustained series of complementary mind-body exercises will ultimately engender enhanced functional integration of cortical and limbic areas controlling voluntary respiratory processes with autonomic brainstem neural pattern generators. Finally, a unified mechanism is proposed that links behaviorally-mediated enhancements of whole-body metabolic advantage to optimization of synchronous regulation of mitochondrial oxygen utilization via recycling of nitrite and nitric oxide by iron-sulfur centers of coupled respiratory complexes and nitrite reductases.

Therapeutic value of stimulating the nitrate-nitrite-nitric oxide pathway to attenuate oxidative stress and restore nitric oxide bioavailability in cardiorenal disease

Cardiovascular disorders including hypertension and associated renal disease are major health problems affecting more than 1.5 billion people worldwide. Apart from nonmodifiable factors such as ageing, family history and gender, both sedentary lifestyle and unhealthy dietary habits are considered as major risk factors. The disorders are interrelated suggesting common pathological pathways. Mechanistically, oxidative stress and compromised function of the nitric oxide synthase (NOS) system leading to endothelial dysfunction and reduction in nitric oxide (NO) bioavailability have been widely implicated and associated with development and progression of disease. New strategies that correct this redox imbalance and increase NO bioactivity may have major clinical implications. The inorganic anions, nitrate and nitrite, are endogenously formed by oxidization of NOS-derived NO, but there are also high amounts of nitrate in our daily diet. In this regard, accumulated evidence over the past two decades demonstrates that these anions can be recycled back to NO and other bioactive nitrogen oxides, thus offering an attractive alternative strategy for therapeutic exploitation. In this review, we describe how dietary stimulation of the nitrate-nitrite-NO pathway affects cardiovascular and renal functions in health and disease via modulation of oxidative stress and NO bioavailability. Clinical studies addressing potential effects on the renal system are still limited, but blood pressure-lowering effects of nitrate supplementation have been demonstrated in healthy and hypertensive subjects as well as in patients with chronic kidney disease. However, larger clinical studies are warranted to reveal whether chronic nitrate treatment can slow-down the progression of cardiorenal disease and associated complications.

Risk factors for hypertensive retinopathy in a Chinese population with hypertension: The Beijing Eye study

Hypertensive retinopathy (HRP) is a clinical feature and systemic manifestation of hypertension. There have been few reports on the risk factors for hypertensive retinopathy in China. The aim of the present study was to describe risk factors associated with HRP in a population-based sample of Chinese patients with hypertension in Beijing. The clinical data of 228 hypertensive patients was retrospectively studied, including 112 patients with retinopathy for the HRP group and 116 patients without retinopathy for the NO-HRP group. Basic clinical data and plasma clinical indicators of the two groups were compared. Logistic regression models were used to assess risk factors associated with HRP. Duration of hypertension, smoking habits, family history of hypertension, plasma level of endothelin-1 (ET-1) and systolic and diastolic blood pressure were significantly increased in the HRP group compared with the NO-HRP group (P<0.05). No significant differences were identified between the two groups for other factors. Logistic regression models indicated that hypertension duration (P<0.001, 95% CI: 0.962-0.988) and ET-1 level (P<0.001, 95% CI: 1.144-1.278) were significantly associated with HRP. The diagnostic threshold of ET-1 to diagnosis HRP was 43.5 ng/l. Of the factors studied, longer hypertension duration and elevated ET-1 level were identified to be risk factors for HRP in patients with hypertension from Beijing. Detecting the plasma level of ET-1 in patients with hypertension may be a useful diagnostic indicator for HRP.

Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation

Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.

Vitamin D Deficiency Harms Patients with Coronary Heart Disease by Enhancing Inflammation

Background

Vitamin D (VD) deficiency and local inflammation of plaque are potential new risk factors and prevention goals for coronary heart disease (CHD).

Material/Methods

This study included 135 CHD patients and 45 chest tightness or chest pain patients (control group). Basic clinical data and serum 25-OH-VD, TNF-α, IL-6, IL-8, and IL-1β of the 2 groups were compared by SPSS 25.0. A CHD rat model was used to explore the potential molecular mechanisms.

Results

The serum 25-OH-VD level in the control group was significantly higher compared to the CHD group, and decreased with the worsening of the CHD condition. Logistic regression found that serum 25-OH-VD was a protective factor in the occurrence of CHD. In CHD patients, the level of serum 25-OH-VD had a negative correlation with serum TNF-α (r=−0.651, P<0.001), IL-6 (r=−0.457, P<0.001), IL-8 (r=−0.755, P<0.001), and IL-1β (r=−0.628, P<0.001). In animal experiments, VD deficiency enhanced the level of serum TC, TG, and LDL-C. VD deficiency could increase the inflammatory response by upregulating the expression of p65 protein and reducing SIRT1 protein expression in heart tissue, thereby inducing or aggravating the state of CHD.

Conclusions

Serum 25-OH-VD was a protective factor in the occurrence of CHD, and VD deficiency could induce or aggravate the state of CHD by enhancing inflammation through the NF-κB pathway.

Impact of Acute Dietary Nitrate Supplementation during Exercise in Hypertensive Women

INTRODUCTION

the aim of the current investigation was to examine if dietary nitrate supplementation would improve vascular control in hypertensive postmenopausal women (PMW). We tested the hypotheses that acute dietary nitrate supplementation would 1) significantly decrease arterial blood pressure (BP) at rest and during exercise, 2) increase limb blood flow during steady-state (SS) exercise, and 3) improve functional sympatholysis during SS exercise.

METHODS

Ten hypertensive PMW underwent a randomized, double-blind, placebo-controlled trial with a nitrate-rich (NR) or nitrate-poor (NP) supplement. Beat-by-beat BP and heart rate were recorded throughout the trial on the nonexercising limb. Forearm blood flow was measured via ultrasonography on the brachial artery of the exercising limb. All patients performed a resting cold pressor test (CPT) (2 min) and then 7 min of submaximal handgrip exercise with a CPT applied during minutes 5-7.

RESULTS

SS systolic (NR, 170 ± 7; NP, 171 ± 37 mm Hg), diastolic (NR, 89 ± 2; NP, 92 ± 2 mm Hg), and mean arterial (NR, 121 ± 4; NP, 123 ± 2 mm Hg) pressures were not different between NP and NR treatment conditions (P > 0.05). During SS exercise, forearm blood flow (NR, 189 ± 8; NP, 218 ± 8 mL·min; P = 0.03) in the NR treatment was significantly lower compared with NP. When the CPT was applied during minutes 6-7 of exercise, forearm vascular conductance was reduced by 15% in the NR condition, but only 7% in the NR condition.

CONCLUSIONS

In summary, an acute NR supplement improved functional sympatholysis by ~50% versus an NP placebo condition. Improvements in functional sympatholysis may have important implications regarding exercise tolerance in hypertensive PMW.

Healthy lifestyle-based approaches for successful vascular aging

This review summarizes a presentation given at the 2016 Gerontological Society of America Annual Meeting as part of the Vascular Aging Workshop. The development of age-related vascular dysfunction increases the risk of cardiovascular disease as well as other chronic age-associated disorders, including chronic kidney disease and Alzheimer's disease. Healthy lifestyle behaviors, most notably regular aerobic exercise and certain dietary patterns, are considered "first-line" strategies for the prevention and/or treatment of vascular dysfunction with aging. Despite the well-established benefits of these strategies, however, many older adults do not meet the recommended guidelines for exercise or consume a healthy diet. Therefore, it is important to establish alternative and/or complementary evidence-based approaches to prevent or reverse age-related vascular dysfunction. Time-efficient forms of exercise training, hormetic exposure to mild environmental stress, fasting "mimicking" dietary paradigms, and nutraceutical/pharmaceutical approaches to favorably modulate cellular and molecular pathways activated by exercise and healthy dietary patterns may hold promise as such alternative approaches. Determining the efficacy of these novel strategies is important to provide alternatives for adults with low adherence to conventional healthy lifestyle practices for healthy vascular aging.

Acute dietary nitrate supplementation does not attenuate oxidative stress or the hemodynamic response during submaximal exercise in hypobaric hypoxia

The purpose of this study was to investigate changes in oxidative stress, arterial oxygen saturation (SaO2), blood pressure (BP), and heart rate (HR) during exercise in hypobaric hypoxia following acute dietary nitrate supplementation. Nine well-trained (maximal oxygen consumption, 60.8 ± 7.8 mL·kg−1·min−1) males (age, 29 ± 7 years) visited the laboratory on 3 occasions, each separated by 1 week. Visit 1 included a maximal aerobic cycling test and five 5-min increasing-intensity exercise bouts in a normobaric environment (1600 m). A single dose of either a nitrate-depleted placebo (PL) or a nitrate-rich beverage (NR; 12.8 mmol nitrate) was consumed 2.5 h prior to exercise during visits 2 and 3 (3500 m) in a double-blind, placebo-controlled, crossover study consisting of a 5-min cycling warm-up and 4 bouts, each 5 min in duration, separated by 4-min periods of passive rest. Exercise wattages were determined during visit 1 and corresponded to 25%, 40%, 50%, 60%, and 70% of normobaric maximal oxygen consumption. Catalase and 8-isoprostane were measured before and after exercise (immediately before and 1 h postexercise, respectively). NR increased plasma nitrite (1.53 ± 0.83 μmol·L−1) compared with PL (0.88 ± 0.56 μmol·L−1) (p < 0.05). In both conditions, postexercise (3500 m) 8-isoprostane (PL, 23.49 ± 3.38 to 60.90 ± 14.95 pg·mL−1; NR, 23.23 ± 4.12 to 52.11 ± 19.76 pg·mL−1) and catalase (PL, 63.89 ± 25.69 to 128.15 ± 41.80 mmol·min−1·mL−1; NR, 78.89 ± 30.95 to 109.96 ± 35.05 mmol·min−1·mL−1) were elevated compared with baseline resting values (p < 0.05). However, both 8-isoprostane and catalase were similar in the 2 groups (PL and NR) (p = 0.217 and p = 0.080, respectively). We concluded that an acute, pre-exercise dose of dietary nitrate yielded no beneficial changes in oxidative stress, SaO2, BP, or HR in healthy, aerobically fit men exercising at 3500 m.

Cardiac effects of 6 months' dietary nitrate and spironolactone in patients with hypertension and with/at risk of type 2 diabetes, in the factorial design, double-blind, randomized controlled VaSera trial

AIMS

The aims of the present study were to explore whether a long-term intervention with dietary nitrate [(NO₃ ^- ), a potential tolerance-free source of beneficial vasoactive nitric oxide] and spironolactone (to oppose aldosterone's potential deleterious cardiovascular effects) improve cardiac structure/function, independently of blood pressure (BP), in patients with/at risk of type 2 diabetes (a population at risk of heart failure).

METHODS

A subsample of participants in our double-blind, randomized, factorial-design intervention (VaSera) trial of active beetroot juice as a nitrate source (≤11.2 mmol) or placebo (nitrate depleted) beetroot juice, and either ≤50 mg spironolactone or ≤16 mg doxazosin (control), had transthoracic cardiac ultrasounds at baseline (n = 105), and at 3 months and 6 months (n = 87) after the start of the intervention. Analysis was by modified intent-to-treat.

RESULTS

Nitrate-containing juice (n = 40) decreased left ventricular (LV) end-diastolic volume {-6.3 [95% confidence interval (CI) -11.1, -1.6] ml} and end-systolic volume [-3.2 (95% CI -5.9, -0.5) ml], and increased end-diastolic mass/volume ratio [+0.04 (95% CI 0.00, 0.07)], relative to placebo juice (n = 47). Spironolactone (n = 44) reduced relative wall thickness compared with doxazosin (n = 43) [-0.01 (95% CI -0.02, -0.00)]. Although spironolactone reduced LV mass index relative to baseline [-1.48 (95% CI -2.08, -0.88) g m^-2.7 ], there was no difference vs. doxazosin [-0.85 (95% CI -1.76, 0.05) g m^-2.7 ]. Spironolactone also decreased the E/A ratio [-0.12 (95% CI -0.19, -0.04)] and increased S' (a tissue-Doppler systolic function index) by 0.52 (95% CI 0.05, 1.0) cm s^-1 . BP did not differ between the juices, or between the drugs.

CONCLUSIONS

Six months' dietary nitrate decreased LV volumes ~5%, representing new, sustained, BP-independent benefits on cardiac structure, extending mechanisms characterized in preclinical models of heart failure. Spironolactone's effects on cardiac remodelling and systolic-diastolic function, although confirmatory, were independent of BP.

Dietary Nitrate from Beetroot Juice for Hypertension: A Systematic Review

According to current therapeutic approaches, a nitrate-dietary supplementation with beetroot juice (BRJ) is postulated as a nutritional strategy that might help to control arterial blood pressure in healthy subjects, pre-hypertensive population, and even patients diagnosed and treated with drugs. In this sense, a systematic review of random clinical trials (RCTs) published from 2008 to 2018 from PubMed/MEDLINE, ScienceDirect, and manual searches was conducted to identify studies examining the relationship between BRJ and blood pressure. The specific inclusion criteria were: (1) RCTs; (2) trials that assessed only the BRJ intake with control group; and (3) trials that reported the effects of this intervention on blood pressure. The search identified 11 studies that met the inclusion criteria. This review was able to demonstrate that BRJ supplementation is a cost-effective strategy that might reduce blood pressure in different populations, probably through the nitrate/nitrite/nitric oxide (NO₃⁻/NO₂⁻/NO) pathway and secondary metabolites found in Beta vulgaris. This easily found and cheap dietary intervention could significantly decrease the risk of suffering cardiovascular events and, in doing so, would help to diminish the mortality rate associated to this pathology. Hence, BRJ supplementation should be promoted as a key component of a healthy lifestyle to control blood pressure in healthy and hypertensive individuals. However, several factors related to BRJ intake (e.g., gender, secondary metabolites present in B. vulgaris, etc.) should be studied more deeply.

Nitrate and Nitrite in Health and Disease

The source of dietary nitrate (NO₃) is mainly green, leafy vegetables, partially absorbed into blood through intestinal mucosa. The recycled nitrate is reabsorbed and concentrated by the salivary glands and then secreted into saliva. In 2012, sialin was first discovered as the mammalian membrane nitrate transporter in salivary glands and plays a key role in circulation of inorganic nitrate, providing a scientific basis for further investigation into the circulation and functions of nitrate. Dietary nitrate can be converted to nitrite (NO₂) by oral commensal bacteria under the tongue or in the stomach, following which nitrite is converted to nitric oxide (NO) through non-enzymatic synthesis. Previously, nitrate and nitrite were thought to be carcinogenic due to the potential formation of nitrogen compounds, whereas the beneficial functions of NO₃^--NO₂^--NO pathway were ignored. Under conditions of hypoxia and ischemia, the production of endogenous NO from L-arginine is inhibited, while the activity of exogenous NO₃^--NO₂^--NO is enhanced. Recently, a greater amount of evidence has shown that nitrate and nitrite serve as a reservoir and perform positive biological NO-like functions. Therefore, exogenous dietary nitrate plays an important role in various physiological activities as an effective supplement of nitrite and NO in human body. Here we generally review the source, circulation and bio-functions of dietary nitrate.

Sex differences in the nitrate-nitrite-NO• pathway: Role of oral nitrate-reducing bacteria

Oral reduction of nitrate to nitrite is dependent on the oral microbiome and is the first step of an alternative mammalian pathway to produce nitric oxide in humans. Preliminary evidence suggests important sex differences in this pathway. We prospectively investigated sex-differences following inorganic nitrate supplementation on nitrate/nitrite levels and vascular function, and separately examined sex differences in oral nitrate reduction, and oral microbiota by 16S rRNA profiling. At baseline, females exhibit higher nitrite levels in all biological matrices despite similar nitrate levels to males. Following inorganic nitrate supplementation, plasma nitrite was increased to a significantly greater extent in females than in males and pulse wave velocity was only reduced in females. Females exhibited higher oral bacterial nitrate-reducing activity at baseline and after nitrate supplementation. Despite these differences, there were no differences in the composition of either the total salivary microbiota or those oral taxa with nitrate reductase genes. Our results demonstrate that females have augmented oral nitrate reduction that contributes to higher nitrite levels at baseline and also after inorganic nitrate supplementation, however this was not associated with differences in microbial composition (clinicaltrials.gov: NCT01583803).

Relationship of dietary nitrate intake from vegetables with cardiovascular disease mortality: a prospective study in a cohort of older Australians

PURPOSE

Short-term trials indicate inorganic nitrate and nitrate-rich vegetables may have vascular health benefits. However, few observational studies have explored the relationship between nitrate intake and long-term cardiovascular disease (CVD) outcomes. The primary aim of this study was to investigate the association of nitrate intake from vegetables with CVD mortality in a sample of older Australians.

METHODS

A subgroup of participants without diabetes or major CVD at baseline (1992-1994) were included from the Blue Mountains Eye Study, a population-based cohort study of men and women aged ≥ 49 years. Diets were evaluated using a validated food frequency questionnaire at baseline, 5 years and 10 years of follow-up. Vegetable nitrate intake was estimated using a comprehensive vegetable nitrate database. Cox proportional hazard regression was used to explore the association between vegetable nitrate intake and CVD mortality.

RESULTS

During 14 years of follow-up, 188/2229 (8.4%) participants died from CVD. In multivariable-adjusted analysis, participants in quartile 2 [69.5-99.6 mg/day; HR 0.53 (95% CI 0.35, 0.82)], quartile 3 [99.7-137.8 mg/day; HR 0.51 (95% CI 0.32, 0.80)], and quartile 4 [> 137.8 mg/day; HR 0.63 (95% CI 0.41, 0.95)] of vegetable nitrate intake had lower hazards for CVD mortality compared to participants in quartile 1 (< 69.5 mg/day).

CONCLUSIONS

In older Australian men and women, vegetable nitrate intake was inversely associated with CVD mortality, independent of lifestyle and cardiovascular risk factors. These findings confirm a recent report that intake of vegetable nitrate lowers the risk of CVD mortality in older women and extend these findings to older men.

A single dose of beetroot juice improves endothelial function but not tissue oxygenation in pregnant women: a randomised clinical trial

Beetroot juice (BJ) consumption has been associated with improved cardiovascular health owing to an increase in NO bioconversion. This study evaluates the effect of BJ consumption on macrovascular endothelial function (flow-mediated dilation (FMD)) and muscle oxygen saturation (StO2) parameters in pregnant women within a randomised, crossover, double-blind design in which twelve pregnant women consumed a single dose (140 ml) of BJ or placebo (PLA). Urinary nitrate was assessed before (T0) and 150 min after BJ/PLA consumption. FMD was used to evaluate macrovascular endothelial function, and near-IR spectroscopy was used to evaluate muscle StO2 parameters during the occlusion and reperfusion phases, which were taken at baseline (PRE) and 120 and 140 min after BJ/PLA consumption, respectively. A significant increase in urinary nitrate was observed at 150 min after BJ consumption when compared with T0 (BJ: 0·20 (sd 0·13) v. T0: 0·02 (sd 0·00), P=0·000) and PLA intervention (PLA: 0·02 (sd 0·00), P=0·001). FMD improved after BJ consumption when compared with PRE (BJ: 11·00 (sd 1·67) v. PRE: 5·53 (sd 1·17), P=0·000) and PLA (5·34 (sd 1·31), P=0·000). No significant difference between PLA and PRE in FMD (P=1·000) was observed. In StO2 parameters, a difference was not observed after BJ consumption compared with PRE and PLA intervention. The data demonstrate that a single dose of 140 ml of BJ consumption improves macrovascular endothelial function, but not StO2 parameters.

Nitrate-Rich Fruit and Vegetable Supplement Reduces Blood Pressure in Normotensive Healthy Young Males without Significantly Altering Flow-Mediated Vasodilation: A Randomized, Double-Blinded, Controlled Trial

Nitric oxide (NO) is a primary vasodilatory factor released from endothelial cells of the peripheral vasculature. NO production is stimulated through enzymatic-dependent mechanisms via NO synthase and from dietary intake of nitrate-containing foods or supplements. We evaluated the efficacy of a nitrate-rich fruit and vegetable liquid supplement (FVS, AMPED NOx, Isagenix International LLC) versus a juice low in nitrates (prune juice, PRU) on circulating nitrates/nitrites as well as cardiovascular parameters in 45 healthy normotensive men (18–40 y). Blood pressure, flow-mediated dilation (FMD), and plasma nitrates and nitrites were measured at baseline and after two weeks of supplementation (2 oz/d). Subjects also completed questionnaires on sleep quality and mood since these measures have been associated with endothelial function. In contrast to PRU, FVS significantly increased plasma nitrates and nitrites (+67%, p < 0.001) and decreased diastolic blood pressure (−9%, p=0.029) after two weeks. The change in FMD for FVS supplementation versus PRU supplementation was not significant (+2% vs. −9%, respectively, p=0.145). Changes in sleep quality or total mood state did not differ between groups after the 2-week study. Thus, the nitrate-rich FVS supplement increased plasma NO and reduced diastolic blood pressure in young normotensive men, but increased plasma NO was not associated with improvements in FMD, mood, or sleep. This trial is registered with ClinicalTrials.gov NCT03486145.

Mechanisms underlying blood pressure reduction by dietary inorganic nitrate

Nitric oxide (NO) importantly contributes to cardiovascular homeostasis by regulating blood flow and maintaining endothelial integrity. Conversely, reduced NO bioavailability is a central feature during natural ageing and in many cardiovascular disorders, including hypertension. The inorganic anions nitrate and nitrite are endogenously formed after oxidation of NO synthase (NOS)-derived NO and are also present in our daily diet. Knowledge accumulated over the past two decades has demonstrated that these anions can be recycled back to NO and other bioactive nitrogen oxides via serial reductions that involve oral commensal bacteria and various enzymatic systems. Intake of inorganic nitrate, which is predominantly found in green leafy vegetables and beets, has a variety of favourable cardiovascular effects. As hypertension is a major risk factor of morbidity and mortality worldwide, much attention has been paid to the blood pressure reducing effect of inorganic nitrate. Here, we describe how dietary nitrate, via stimulation of the nitrate-nitrite-NO pathway, affects various organ systems and discuss underlying mechanisms that may contribute to the observed blood pressure-lowering effect.

Postulating the major environmental condition resulting in the expression of essential hypertension and its associated cardiovascular diseases: Dietary imprudence in daily selection of foods in respect of their potassium and sodium content resulting in oxidative stress-induced dysfunction of the vascular endothelium, vascular smooth muscle, and perivascular tissues

We hypothesize that the major environmental determinant of the expression of essential hypertension in America and other Westernized countries is dietary imprudence in respect of the consumption of daily combinations of foods containing suboptimal amounts of potassium and blood pressure-lowering phytochemicals, and supraphysiological amounts of sodium. We offer as premise that Americans on average consume suboptimal amounts of potassium and blood pressure-lowering phytochemicals, and physiologically excessive amounts of sodium, and that such dietary imprudence leads to essential hypertension through oxidative stress-induced vascular endothelial and smooth muscle dysfunction. Such dysfunctions restrict nitric oxide bioavailability, impairing endothelial cell-mediated relaxation of the underlying vascular smooth muscle, initiating and maintaining inappropriately increased peripheral and renal vascular resistance. The biochemical steps from oxidative stress to vascular endothelial dysfunction and its pernicious cardiovascular consequences are well established and generally accepted. The unique aspect of our hypothesis resides in the contention that Americans' habitual consumption of foods resulting in suboptimal dietary intake of potassium and supraphysiological intake of sodium result in oxidative stress, the degree of which, we suggest, will correlate with the degree of deviation of potassium and sodium intake from optimal. Because suboptimal intakes of potassium reflect suboptimal intakes of fruits and vegetables, associated contributors to oxidative stress include suboptimal intakes of magnesium, nitrate, polyphenols, carotenoids, and other phytochemical antioxidants for which fruits and vegetables contain abundant amounts. Currently Americans consume potassium-to-sodium in molar ratios of less than or close to 1.0 and the Institute of Medicine (IOM) recommends a molar ratio of 1.2. Ancestral diets to which we are physiologically adapted range from molar ratios of 5.0 to 10.0 or higher. Accordingly, we suggest that the average American is usually afflicted with oxidative stress-induced vascular endothelial dysfunction, and therefore the standards for normal blood pressure and pre-hypertension often reflect a degree of clinically significant hypertension. In this article, we provide support for those contentions, and indicate the findings that the hypothesis predicts.

Benefit-risk analysis for foods (BRAFO): Evaluation of exposure to dietary nitrates

Dietary nitrate has been associated with health benefits as well as potential risks, thus presenting a paradox for consumers and health professionals. To address the issue, we applied the Benefit-Risk Analysis for Foods (BRAFO) framework to evaluate dietary exposure to nitrate by considering how the risks and benefits might vary under the reference scenario of the acceptable daily intake (ADI) set forth by JECFA (3.7 mg/kg-day), or under an alternative scenario of a higher ADI (independently developed herein). Results demonstrated that risk, as conservatively characterized by various toxicological benchmarks, was present at levels ranging from the current ADI value of 3.7 mg/kg-day (lowest end of the range) to >15 mg/kg-day. When these ADI values, both established by regulatory bodies as well as independently herein were compared to intakes associated with benefits (decreased blood pressure observed following repeated exposure to nitrates ∼4-18 mg/kg-day), along with considerations of current dietary exposures associated with healthy diets, the alternative scenario allowed for benefits without incurring additional risk. For consumers aged 12 weeks and older, ADI values ∼12-17 mg/kg-day-based on more reliable data than used to derive the current ADI-allow benefits to be realized while still protecting public health. The assessment serves as a case study in how benefits can be considered in a risk assessment paradigm for foods, thus providing useful information to decision makers.

A randomised controlled trial exploring the effects of different beverages consumed alongside a nitrate-rich meal on systemic blood pressure

BACKGROUND:

Ingestion of nitrate (NO₃^-)-containing vegetables, alcohol and polyphenols, separately, can reduce blood pressure (BP). However, the pharmacokinetic response to the combined ingestion of NO₃^- and polyphenol-rich or low polyphenol alcoholic beverages is unknown.

AIM:

The aim of this study was to investigate how the consumption of low and high polyphenolic alcoholic beverages combined with a NO₃^--rich meal can influence NO₃^- metabolism and systemic BP.

METHODS:

In a randomised, crossover trial, 12 normotensive males (age 25 ± 5 years) ingested an acute dose of NO₃^- (∼6.05 mmol) in the form of a green leafy salad, in combination with either a polyphenol-rich red wine (NIT-RW), a low polyphenol alcoholic beverage (vodka; NIT-A) or water (NIT-CON). Participants also consumed a low NO₃^- salad and water as a control (CON; ∼0.69 mmol NO₃^-). BP and plasma, salivary and urinary [NO₃^-] and nitrite ([NO₂^-]) were determined before and up to 5 h post ingestion.

RESULTS:

Each NO₃^--rich condition elevated nitric oxide (NO) biomarkers when compared with CON ( P < 0.05). The peak rise in plasma [NO₂^-] occurred 1 h after NIT-RW (292 ± 210 nM) and 2 h after NIT-A (318 ± 186 nM) and NIT-CON (367 ± 179 nM). Systolic BP was reduced 2 h post consumption of NIT-RW (-4 mmHg), NIT-A (-3 mmHg) and NIT-CON (-2 mmHg) compared with CON ( P < 0.05). Diastolic BP and mean arterial pressure were also lower in NIT-RW and NIT-A compared with NIT-CON ( P < 0.05).

CONCLUSIONS:

A NO₃^--rich meal, consumed with or without an alcoholic beverage, increases plasma [NO₂^-] and lowers systemic BP for 2-3 h post ingestion.

Effects of dietary nitrate supplementation, from beetroot juice, on blood pressure in hypertensive pregnant women: A randomised, double-blind, placebo-controlled feasibility trial

Chronic hypertension in pregnancy is associated with significant adverse pregnancy outcomes, increasing the risk of pre-eclampsia, fetal growth restriction and preterm birth. Dietary nitrate, abundant in green leafy vegetables and beetroot, is reduced in vivo to nitrite and subsequently nitric oxide, and has been demonstrated to lower blood pressure, improve vascular compliance and enhance blood flow in non-pregnant humans and animals. The primary aims of this study were to determine the acceptability and efficacy of dietary nitrate supplementation, in the form of beetroot juice, to lower blood pressure in hypertensive pregnant women. In this double-blind, placebo-controlled feasibility trial, 40 pregnant women received either daily nitrate supplementation (70 mL beetroot juice, n = 20) or placebo (70 mL nitrate-depleted beetroot juice, n = 20) for 8 days. Blood pressure, cardiovascular function and uteroplacental blood flow was assessed at baseline and following acute (3 h) and prolonged (8 days) supplementation. Plasma and salivary samples were collected for analysis of nitrate and nitrite concentrations and acceptability of this dietary intervention was assessed based on questionnaire feedback. Dietary nitrate significantly increased plasma and salivary nitrate/nitrite concentrations compared with placebo juice (p < 0.001), with marked variation between women. Compared with placebo, there was no overall reduction in blood pressure in the nitrate-treated group; however there was a highly significant correlation between changes in plasma nitrite concentrations and changes in diastolic blood pressure in the nitrate-treated arm only (r = -0.6481; p = 0.0042). Beetroot juice supplementation was an acceptable dietary intervention to 97% of women. This trial confirms acceptability and potential efficacy of dietary nitrate supplementation in pregnant women. Conversion of nitrate to nitrite critically involves oral bacterial nitrate reductase activities. We speculate that differences in efficacy of nitrate supplementation relate to differences in the oral microbiome, which will be investigated in future studies.

Drinking Water Nitrate and Human Health: An Updated Review

Nitrate levels in our water resources have increased in many areas of the world largely due to applications of inorganic fertilizer and animal manure in agricultural areas. The regulatory limit for nitrate in public drinking water supplies was set to protect against infant methemoglobinemia, but other health effects were not considered. Risk of specific cancers and birth defects may be increased when nitrate is ingested under conditions that increase formation of N-nitroso compounds. We previously reviewed epidemiologic studies before 2005 of nitrate intake from drinking water and cancer, adverse reproductive outcomes and other health effects. Since that review, more than 30 epidemiologic studies have evaluated drinking water nitrate and these outcomes. The most common endpoints studied were colorectal cancer, bladder, and breast cancer (three studies each), and thyroid disease (four studies). Considering all studies, the strongest evidence for a relationship between drinking water nitrate ingestion and adverse health outcomes (besides methemoglobinemia) is for colorectal cancer, thyroid disease, and neural tube defects. Many studies observed increased risk with ingestion of water nitrate levels that were below regulatory limits. Future studies of these and other health outcomes should include improved exposure assessment and accurate characterization of individual factors that affect endogenous nitrosation.

Modulation of the orthostatic blood pressure response by acute nitrate consumption is dependent upon ethnic origin

Orthostatic stress triggers a response to maintain cerebral perfusion and prevent syncope. Given the hypotensive effects of inorganic nitrate this response to orthostasis may be altered by acute supplementation with inorganic nitrate and modified by ethnic origin. Caucasian and SE Asian (n = 30 for both), were recruited and subjected to an 'active stand test' and brachial artery blood pressure (BP), digit blood flow and ECG were recorded. Following inorganic nitrate supplementation, (10 mg/kg body mass) the tests were repeated. For both Caucasian and SE Asians transition to standing increased diastolic pressure (DP) and heart rate (HR) (P < 0.001 for both) and by calculation increased rate-pressure product (P < 0.001) and decreased pulse pressure (P < 0.01 for both) indicative of decreased ventricular filling. Nitrate supplementation decreased both DP (P < 0.001) and HR (P < 0.001). Assessment of HR variability suggested sympathetic nerve activity, was higher throughout in Caucasians (P < 0.05) coupled with higher parasympathetic tone (P < 0.01). Nitrate had no effect on cardiac autonomic nerve activity, as estimated using HR variability, for supine or standing subjects. The tachycardia and hypertension associated with orthostatic stress were preserved in both Caucasian and SE Asian subjects, however, we highlight possible differences in autonomic nervous system activity between Caucasians and SE Asians. SE Asians are resistant to the hypotensive effects of inorganic nitrate supplementation suggesting the absence of a crucial mechanism for activation of the nitrate-nitrite-nitric oxide system.

Metabolic Effects of Dietary Nitrate in Health and Disease

Nitric oxide (NO), generated from L-arginine and oxygen by NO synthases, is a pleiotropic signaling molecule involved in cardiovascular and metabolic regulation. More recently, an alternative pathway for the formation of this free radical has been explored. The inorganic anions nitrate (NO₃^-) and nitrite (NO₂^-), originating from dietary and endogenous sources, generate NO bioactivity in a process involving seemingly symbiotic oral bacteria and host enzymes in blood and tissues. The described cardio-metabolic effects of dietary nitrate from experimental and clinical studies include lowering of blood pressure, improved endothelial function, increased exercise performance, and reversal of metabolic syndrome, as well as antidiabetic effects. The mechanisms underlying the salutary metabolic effects of nitrate are being revealed and include interaction with mitochondrial respiration, activation of key metabolic regulatory pathways, and reduction of oxidative stress. Here we review the recent advances in the nitrate-nitrite-NO pathway, focusing on metabolic effects in health and disease.

Nitrate-rich vegetables do not lower blood pressure in individuals with mildly elevated blood pressure: a 4-wk randomized controlled crossover trial

Background

Emerging evidence suggests that increasing intakes of nitrate-rich vegetables may be an effective approach to reduce blood pressure.

Objective

Our primary aim was to determine whether daily consumption of nitrate-rich vegetables over 4 wk would result in lower blood pressure.

Design

Thirty participants with prehypertension or untreated grade 1 hypertension were recruited to a randomized controlled crossover trial with 4-wk treatment periods separated by 4-wk washout periods. Participants completed 3 treatments in random order: 1) increased intake (∼200 g/d) of nitrate-rich vegetables [high-nitrate (HN); ∼150 mg nitrate/d], 2) increased intake (∼200 g/d) of nitrate-poor vegetables [low-nitrate (LN); ∼22 mg nitrate/d], and 3) no increase in vegetables (control; ∼6 mg nitrate/d). Compliance was assessed with the use of food diaries and by measuring plasma nitrate and carotenoids. Nitrate metabolism was assessed with the use of plasma, salivary, and urinary nitrate and nitrite concentrations. The primary outcome was blood pressure assessed by using 24-h ambulatory, home, and clinic measurements. Secondary outcomes included measures of arterial stiffness.

Results

Plasma nitrate and nitrite concentrations increased with the HN treatment in comparison to the LN and control treatments (P < 0.001). Plasma carotenoids increased with the HN and LN treatments compared with the control (P < 0.01). HN treatment did not reduce systolic blood pressure [24-h ambulatory-HN: 127.4 ± 1.1 mm Hg; LN: 128.6 ± 1.1 mm Hg; control: 126.2 ± 1.1 mm Hg (P = 0.20); home-HN: 127.4 ± 0.7 mm Hg; LN: 128.7 ± 0.7 mm Hg; control: 128.3 ± 0.7 mm Hg (P = 0.36); clinic-HN: 128.4 ± 1.3 mm Hg; LN: 130.3 ± 1.3 mm Hg; control: 129.8 ± 1.3 mm Hg (P = 0.49)] or diastolic blood pressure compared with LN and control treatments (P > 0.05) after adjustment for pretreatment values, treatment period, and treatment order. Similarly, no differences were observed between treatments for arterial stiffness measures (P > 0.05).

Conclusion

Increased intake of nitrate-rich vegetables did not lower blood pressure in prehypertensive or untreated grade 1 hypertensive individuals when compared with increased intake of nitrate-poor vegetables and no increase in vegetables. This trial was registered at www.anzctr.org.au as ACTRN12615000194561.

Discrete physiological effects of beetroot juice and potassium nitrate supplementation following 4-wk sprint interval training

The physiological and exercise performance adaptations to sprint interval training (SIT) may be modified by dietary nitrate ([Formula: see text]) supplementation. However, it is possible that different types of [Formula: see text] supplementation evoke divergent physiological and performance adaptations to SIT. The purpose of this study was to compare the effects of 4-wk SIT with and without concurrent dietary [Formula: see text] supplementation administered as either [Formula: see text]-rich beetroot juice (BR) or potassium [Formula: see text] (KNO3). Thirty recreationally active subjects completed a battery of exercise tests before and after a 4-wk intervention in which they were allocated to one of three groups: 1) SIT undertaken without dietary [Formula: see text] supplementation (SIT); 2) SIT accompanied by concurrent BR supplementation (SIT + BR); or 3) SIT accompanied by concurrent KNO3 supplementation (SIT + KNO3). During severe-intensity exercise, V̇o2peak and time to task failure were improved to a greater extent with SIT + BR than SIT and SIT + KNO3 ( P < 0.05). There was also a greater reduction in the accumulation of muscle lactate at 3 min of severe-intensity exercise in SIT + BR compared with SIT + KNO3 ( P < 0.05). Plasma [Formula: see text] concentration fell to a greater extent during severe-intensity exercise in SIT + BR compared with SIT and SIT + KNO3 ( P < 0.05). There were no differences between groups in the reduction in the muscle phosphocreatine recovery time constant from pre- to postintervention ( P > 0.05). These findings indicate that 4-wk SIT with concurrent BR supplementation results in greater exercise capacity adaptations compared with SIT alone and SIT with concurrent KNO3 supplementation. This may be the result of greater NO-mediated signaling in SIT + BR compared with SIT + KNO3.

NEW & NOTEWORTHY We compared the influence of different forms of dietary nitrate supplementation on the physiological and performance adaptations to sprint interval training (SIT). Compared with SIT alone, supplementation with nitrate-rich beetroot juice, but not potassium [Formula: see text], enhanced some physiological adaptations to training.