Food sources of nitrates and nitrites: the physiologic context for potential health benefits

Nitrates/Nitrites in Food-Risk for Nitrosative Stress and Benefits

In the context of impact on human health, nitrite/nitrate and related nitrogen species such as nitric oxide (NO) are a matter of increasing scientific controversy. An increase in the content of reactive nitrogen species may result in nitrosative stress-a deleterious process, which can be an important mediator of damage to cell structures, including lipids, membranes, proteins and DNA. Nitrates and nitrites are widespread in the environment and occur naturally in foods of plant origin as a part of the nitrogen cycle. Additionally, these compounds are used as additives to improve food quality and protect against microbial contamination and chemical changes. Some vegetables such as raw spinach, beets, celery and lettuce are considered to contain high concentrations of nitrates. Due to the high consumption of vegetables, they have been identified as the primary source of nitrates in the human diet. Processed meats are another source of nitrites in our diet because the meat industry uses nitrates/nitrites as additives in the meat curing process. Although the vast majority of consumed nitrates and nitrites come from natural vegetables and fruits rather than food additives, there is currently a great deal of consumer pressure for the production of meat products free of or with reduced quantities of these compounds. This is because, for years, the cancer risks of nitrates/nitrites have been considered, since they potentially convert into the nitrosamines that have carcinogenic effects. This has resulted in the development and rapid expansion of meat products processed with plant-derived nitrates as nitrite alternatives in meat products. On the other hand, recently, these two ions have been discussed as essential nutrients which allow nitric oxide production and thus help cardiovascular health. Thus, this manuscript reviews the main sources of dietary exposure to nitrates and nitrites, metabolism of nitrites/nitrates, and health concerns related to dietary nitrites/nitrates, with particular emphasis on the effect on nitrosative stress, the role of nitrites/nitrates in meat products and alternatives to these additives used in meat products.

Chlorogenic acid improves lipid membrane peroxidation and morphological changes in nitrite-induced erythrocyte model of methemoglobinemia

Nitrite salts are widely presented in food and their hazardous effects have been well documented. In this study, we evaluated the protective capacity of chlorogenic acid (CGA) against sodium nitrite (NaNO₂₎ -induced damage to rat erythrocytes. Two dosing regimens of CGA were undertaken to alleviate the erythrocyte injury induced by NaNO₂ . We examined the cell fragility, the level of methemoglobin and oxidative stress parameters of each treated group. In result, as compared to the CGA post-incubation, co-incubation of CGA with NaNO₂ decreased the content of advanced oxidation protein products. The protective capacity of CGA was superior to its remedial effect. We infer that the reaction of CGA and NaNO₂ may suppress the cytotoxicity of nitrite on erythrocytes and avoid the generation of oxidative stress induced by NaNO₂ . Our results suggest a novel diet strategy for preventing the adverse effects of nitrite in those people with exposure to nitrite. PRACTICAL APPLICATIONS: Nitrite is ubiquitous in our environment and can also be formed from nitrogenous compounds by microorganisms which exist in the soil, water, and saliva. Several researches have been performed to explore the protection of natural products on the toxic effects of Nitrite. In this study, exogenous chlorogenic acid (CGA) is able to avert the membrane damage, lipid peroxidation, and morphology in nitrite-induced erythrocytes. The protective capacity of CGA shows superior to the remediate effect of CGA against NaNO₂ caused damage to erythrocytes. These results suggest a novel diet strategy for preventing the adverse effects of NaNO₂ in those people with acute exposure to nitrite.

Incorporating Exogenous and Endogenous Exposures into Dietary Risk Assessment of Nitrates and Nitrites in Vegetables: A Probabilistic Integrated Toxicokinetic Modeling Approach

This study aimed to estimate the dietary risk of nitrates and nitrites in vegetables based on internal dose in a probabilistic manner by integrating exogenous exposure based on measured concentrations in vegetables with endogenous exposure using a toxicokinetic (TK) model. We optimized and validated a previous TK model and incorporated Monte Carlo simulations to account for variability across different age populations for predicting internal dose. High levels of nitrates were detected in leafy vegetables (from 545 ± 274 to 1641 ± 873 mg/kg). Nitrite contents of vegetables were generally low (from 1.26 ± 1.40 to 8.20 ± 14.1 mg/kg). The dietary risk was found to be different based on internal versus external dose, suggesting that it is critical to include endogenous nitrite formation into risk assessment. Nitrate and nitrite exposure from vegetables is unlikely to result in appreciable risks for most populations but may be a potential risk for preschoolers.

Effects of Fennel Seed Powder Supplementation on Growth Performance, Carcass Characteristics, Meat Quality, and Economic Efficiency of Broilers under Thermoneutral and Chronic Heat Stress Conditions

Simple Summary

Nowadays, great attention has been given to phytogenic products as a growth enhancer due to their safety and eco-friendly influences on animal nutrition. Thus, this investigation looked at the use of fennel seed powder at 0, 1.6, and 3.2% as a dietary additive on the performance, carcass traits, meat quality, and efficiency of the production of broiler chickens raised under thermoneutral and chronic heat stress conditions. In essence, 3.2% fennel seed powder in the diet of broilers enhanced the growth rate under chronic heat stress and decreased breast meat redness and temperature, suggesting that 3.2% fennel seed could be used as an agent for enhancing the broiler’s tolerance during chronic heat stress (CHS) condition from 19 to 41 days of age.

Abstract

Nowadays, phytogenic products have received great attention as a growth promoter due to their safety and environmentally friendly effect as a replacement for classical growth promoters such as antibiotics in animal nutrition. Thus, this research seeks the possibility of using fennel seed powder (FSP) as a dietary additive from 19 to 41 days of age on productive performance, carcass traits, meat quality, and production efficiency of broiler chickens raised under thermoneutral and chronic heat stress conditions. Thus, 216 one-day-old Ross-308 broiler chicks were divided into two equal groups. The first group was placed in an independent temperature-controlled room at 23 ± 2 °C. The broiler chicks from the second group were placed in a heat-stressed room and exposed to chronic heat stress conditions (32 ± 2 °C) for seven hours per day from 8 a.m. to 3 p.m. The experimental design was 2 × 3 factorial including two environmental temperatures (thermoneutral vs chronic heat stress) and three experimental diets that contained 0, 1.6, and 3.2% FSP. The chickens were randomly assigned to 18-floor pens per room temperature, representing six replicates per treatment and six birds per replicate. The results showed that dietary fennel seed powder during days 19–41 of age enhanced the growth rate of broiler chickens and improved breast meat redness and reduced temperature under chronic heat stress. In conclusion, 3.2% of fennel seed powder could be used as an agent for enhancing the broiler’s tolerance during chronic heat stress condition from 19 to 41 days of age. Moreover, it is necessary to study in further detail the nitrite and nitrate contents in FSP and their impacts on muscle redness (a*) as well as muscle temperature.

The nitrate content of fresh and cooked vegetables and their health-related risks

BACKGROUND

Vegetables are the most important source of nitrates in the human diet. During various processes in the body, nitrates are converted into nitrites, which causes various diseases, such as blue baby syndrome and cancer. This study aimed to determine the concentration of nitrates in several vegetable farms in Sanandaj city and to evaluate their health-related risks.

METHODS

This descriptive cross-sectional study was conducted from October 2017 to July 2018. A total of 90 samples were taken from nine farms. Soil and water sampling was also carried out. All stages of sample preparation and extraction were carried out according to Food Standards 2-16721, and the nitrate measurements were performed using ion chromatography (Compact IC Plus 882 Model, Metrohm, Switzerland). A health risk assessment was performed using the non-carcinogenic risk assessment.

RESULTS

This study's results showed that the nitrate concertation in all vegetables was less than National Iranian Vegetable Nitrate Standard. Nitrate levels in leafy vegetables were higher than in root vegetables, and the root vegetables levels were higher than those in Fruit vegetable. The nitrate level in vegetables in autumn was higher than in spring. The cooking process reduced the raw vegetables' nitrate content from 4.094% to 13.407%, while the frying process increased the vegetables' nitrate content from 12.46% to 29.93%. The highest health risk level in raw, cooked and fried vegetables was parsley, parsley and beet leaves, respectively, and the lowest in all categories was tomatoes. Generally, the highest health risk was related to fried beet leaves, and the lowest was raw tomatoes. In addition, each of the abovementioned relationships between vegetables' nitrate levels and the harvest season, type of processing procedure and type of vegetables was significant (p < 0.05). The irrigation water's nitrate concentration in all fields was between 12.36 and 33.14 mg/l. The soil contained nitrate levels of between 4.35 and 9.7 mg/kg.

CONCLUSION

Based on this study, we can conclude that the amount of nitrates in raw vegetables was lower than the standard limit's level and that this level does not cause health problems for consumers.

Adherence to a Dietary Approach to Stop Hypertension (DASH)-Style in Relation to Daytime Sleepiness

BACKGROUND

The beneficial impact of adherence to a DASH diet on several metabolic conditions and psychological well-being has been shown previously. Dietary modification can affect sleep quality. Thus, the aim of this present study was to investigate the correlation between adherence to the DASH diet and daytime sleepiness score in adolescent girls.

METHODS

A total of 535 adolescent girls aged between 12 and 18 years old were recruited from different regions of Khorasan Razavi in northeastern of Iran, using a random cluster sampling method. DASH scores were determined according to the method of Fung et al. A Persian translation of the Epworth Sleepiness Scale (ESS-IR) was used to assess of daytime sleepiness. To investigate the correlation between DASH-style diet and daytime sleepiness score, we applied logistic regression analysis in crude and adjusted models.

RESULTS

As may be expected, participants with the greatest adherence to the DASH diet had significantly higher intakes of fruits, vegetables, low-fat dairy products, fish and nuts, and lower consumption of refined grains, red and processed meat, sugar-sweetened beverages and sweets. There was an inverse correlation between adherence to the DASH-style diet and scores for daytime sleepiness in crude model (β= -0.12; P=0.005). These findings were remained significant after adjustment for confounding variables (β= -0.08 P=0.04).

CONCLUSION

There is an inverse correlation between adherence to DASH diet and daytime sleepiness score. Further studies, particularly longitudinal studies, are required to determine whether dietary intervention may improve daytime sleepiness.

Treatment with Nitrate, but Not Nitrite, Lowers the Oxygen Cost of Exercise and Decreases Glycolytic Intermediates While Increasing Fatty Acid Metabolites in Exercised Zebrafish

BACKGROUND

Dietary nitrate improves exercise performance by reducing the oxygen cost of exercise, although the mechanisms responsible are not fully understood.

OBJECTIVES

We tested the hypothesis that nitrate and nitrite treatment would lower the oxygen cost of exercise by improving mitochondrial function and stimulating changes in the availability of metabolic fuels for energy production.

METHODS

We treated 9-mo-old zebrafish with nitrate (sodium nitrate, 606.9 mg/L), nitrite (sodium nitrite, 19.5 mg/L), or control (no treatment) water for 21 d. We measured oxygen consumption during a 2-h, strenuous exercise test; assessed the respiration of skeletal muscle mitochondria; and performed untargeted metabolomics on treated fish, with and without exercise.

RESULTS

Nitrate and nitrite treatment increased blood nitrate and nitrite levels. Nitrate treatment significantly lowered the oxygen cost of exercise, as compared with pretreatment values. In contrast, nitrite treatment significantly increased oxygen consumption with exercise. Nitrate and nitrite treatments did not change mitochondrial function measured ex vivo, but significantly increased the abundances of ATP, ADP, lactate, glycolytic intermediates (e.g., fructose 1,6-bisphosphate), tricarboxylic acid (TCA) cycle intermediates (e.g., succinate), and ketone bodies (e.g., β-hydroxybutyrate) by 1.8- to 3.8-fold, relative to controls. Exercise significantly depleted glycolytic and TCA intermediates in nitrate- and nitrite-treated fish, as compared with their rested counterparts, while exercise did not change, or increased, these metabolites in control fish. There was a significant net depletion of fatty acids, acyl carnitines, and ketone bodies in exercised, nitrite-treated fish (2- to 4-fold), while exercise increased net fatty acids and acyl carnitines in nitrate-treated fish (1.5- to 12-fold), relative to their treated and rested counterparts.

CONCLUSIONS

Nitrate and nitrite treatment increased the availability of metabolic fuels (ATP, glycolytic and TCA intermediates, lactate, and ketone bodies) in rested zebrafish. Nitrate treatment may improve exercise performance, in part, by stimulating the preferential use of fuels that require less oxygen for energy production.

Chemical composition and bioactive properties of Cichorium spinosum L. in relation to nitrate/ammonium nitrogen ratio

BACKGROUND

Nitrogenous fertilizers may affect the yield and quality of leafy vegetables via the application rate and nitrogen form. In the present study, the effect of the nitrate:ammonium nitrogen ratio in the nutrient solution on the chemical composition and bioactive properties of Cichorium spinosum leaves was evaluated. For this purpose, C. spinosum plants were fertigated with nutrient solution containing different ratios of nitrate: ammonium nitrogen: (i) 100:0 NO₃ -N:NH₄ -N; (ii) 75:25 NO₃ -N:NH₄ -N; (iii) 50:50 NO₃ -N:NH₄ -N; (iv) 25:75 NO₃ -N:NH₄ -N; and (v) 0:100 NO₃ -N:NH₄ -N of total nitrogen; as well as (vi) 100% ureic nitrogen.

RESULTS

The only detected tocopherol isoforms were α- and δ-tocopherol, which were positively affected by nitrate nitrogen (100:0 NO₃ -N:NH₄ -N). Similar results were observed for individual and total organic acids. The main detected sugars were fructose, glucose and sucrose, with a varied effect of nutrient solution composition on their content, whereas total sugar concentration was positively affected by a balanced or a slightly increased proportion of NH₄ -N (50:50 and 25:75 NO₃ -N:NH₄ -N). The fatty acids profile was beneficially affected by the highest NH₄ -N ratio (0:100 NO₃ -N:NH₄ -N), whereas higher amounts of NO₃ ^- than NH₄ ⁺ nitrogen (75:25 NO₃ -N:NH₄ -N) resulted in a higher content of total phenolic compounds. Finally, no cytotoxic effects were observed against non-tumor (PLP2, HeLa) and tumor (HepG2, MCF-7, NCI-H460) cell lines for any of the studied nutrient solutions.

CONCLUSION

The modulation of NO₃ -N:NH₄ -N ratio in the nutrient solution supplied to C. spinosum may enhance the content of desirable health-promoting compounds and reduce the content of antinutrients, thus increasing the overall quality of the final product without compromising yield. © 2019 Society of Chemical Industry.

Environmental exposure to perchlorate, nitrate, and thiocyanate in relation to obesity: A population-based study

BACKGROUND

Perchlorate, nitrate, and thiocyanate are well-known thyroid disrupters and may contribute to changes in body weight. However, the associations between environmental exposure to these chemicals and obesity-related outcomes remain unclear.

OBJECTIVES

We aim to examine the urinary levels of perchlorate, nitrate, and thiocyanate and their associations with obesity and abdominal obesity in the U.S.

METHODS

Here, we investigated the data of 16,265 adults aged 20-85 years from the National Health and Nutritional Examination Survey (NHANES) in 2001-2014. Urinary levels of perchlorate, nitrate, and thiocyanate were measured by ion chromatography combined with electrospray tandem mass spectrometry. Obesity and abdominal obesity were defined by the body mass index and waist circumference, respectively. Logistic regression models were used to estimate the associations.

RESULTS

Overall, 5794 (35.6%) cases of obesity and 9090 cases (55.9%) of abdominal obesity were observed among the participants. In multivariable-adjusted logistic regression models, urinary nitrate was inversely associated with obesity (p = 0.0022 for trend), while urinary thiocyanate was positively related to obesity (p < 0.001 for trend). Compared with the lowest quartile, the odds ratios with 95% confidence intervals (CIs) across increasing quartiles were 0.95 (95% CI, 0.83-1.08), 0.88 (0.75-1.03), and 0.74 (0.60-0.90) for urinary nitrate and 1.31 (1.16-1.48), 1.53 (1.36-1.73), and 1.73 (1.47-2.03) for urinary thiocyanate. Urinary perchlorate was not correlated with obesity. Similar associations were also found between exposure to these chemicals and abdominal obesity.

CONCLUSIONS

A higher exposure to urinary nitrate was associated with a lower risk of obesity, while a positive association was observed for urinary thiocyanate. These findings emphasize the need to longitudinally evaluate environmental exposure to perchlorate, nitrate, and thiocyanate with respect to their effect on obesity in humans.

Effects of dietary nitrate and folate supplementation on blood pressure in hypertensive Tanzanians: Design and baseline characteristics of a feasibility trial

The burden of hypertension in Sub-Saharan African countries is rising. Low-cost and effective interventions are needed to mitigate these alarming trends. No evidence is available on the use of dietary nitrate for treating hypertension in African populations. The objectives of this study are to assess the feasibility and efficacy of using beetroot and folate as a combined dietary intervention to treat Tanzanian adults with pre- and mild to moderate hypertension. This was a three-arm double-blind, placebo-controlled, parallel randomised clinical trial conducted within the Hai Demographic Surveillance Site in the Kilimanjaro region in Tanzania. 48 participants were randomised to one of three groups for a 60-day intervention period. Group 1: Combined dietary intervention (beetroot juice and folate), Group 2: Single dietary intervention (beetroot juice and placebo capsule), and Group 3: Control group (placebo beetroot juice and placebo capsule). The primary outcome of the trial was to evaluate the feasibility of the study in a low-income setting. Trial assessments included resting clinic and ambulatory 24-hr blood pressure measurements, lifestyle and dietary questionnaires and collection of biological samples. Our cohort included 8 (16.7%) males and 40 (83.3%) females with mean age 60.7 years (SD 6.5). The mean (SD) BMI, clinic systolic blood pressure and ambulatory systolic blood pressure at baseline were 27.6 kg/m2 (5.4), 151.0 (19.4), and 140.4 (15.0) mmHg, respectively. Eight (16.7%) participants were classified as pre-hypertensive, 20 (41.7%) as stage-1 hypertensive, and 20 (41.7%) as stage-2 hypertensive. Overall, the results support the feasibility of a study of this nature within a hypertensive African population.

TRIAL REGISTRATION NUMBER

ISRCTN67978523.

The effect of pomegranate on oxidative stress parameters: A systematic review and meta-analysis

OBJECTIVE

Pomegranate contains remarkable amounts of phenolic ingredients and it has been related to the antioxidant capacity of this fruit. Several primary studies show that pomegranate intake can improve antioxidant status. The objective of this systematic review and meta-analysis consisted in investigating the effect of pomegranate on oxidative stress (OS) parameters.

METHODS

A comprehensive electronic database search in Scopus, Web of science, Embase, Cochrane library and Medline was performed to identify eligible randomized controlled trials (RCTs). A meta-analysis of included studies was performed on selected variables using a random-effects model. Quality assessment was conducted by means of Cochrane risk of bias assessment tool.

RESULTS

Systematic search yielded 575 references. A total of 11 RCTs reporting data from 484 participants included. Meta-analysis of data from 11 included RCTs did not support convincing evidence as to a significant increasing effect of pomegranate intake in TAC (SMD: 0.43 ; 95 %CI: -0.19, 1.06), Gpx (SMD: 0.18, 95 % CI: -0.25, 0.62, p = 0.4) and paraxonase (SMD: 0.36, 95 % CI: -0.50, 1.22, p= 0.41) as well as not significant decrease in Malondialdehyde (MDA) (SMD: -0.81, 95 % CI: -1.79, 0.09, P = 0.08).

CONCLUSION

Future well-designed clinical trials are needed before definite conclusive claims can be made about the effect of pomegranate on OS parameters.

Inorganic Nitrate Supplementation for Cardiovascular Health

Nitric oxide (NO) is continually produced by the enzyme nitric oxide synthase (NOS) and is essential to the control and effectiveness of the cardiovascular system. However, there is a substantial reduction in NOS activity with aging that can lead to the development of hypertension and other cardiovascular complications. Fortunately, NO can also be produced by the sequential reduction of inorganic nitrate to nitrite and then to NO. Nitric oxide from inorganic nitrate supplementation has been found to have the same cardioprotective benefits of NO produced by NOS. Moreover, it can effectively compensate for declining NOS activity due to aging or NOS inhibition by oxidative stress, hypoxia, or other factors. This review covers some of the major cardiovascular regulatory actions of NO and presents evidence that NO from inorganic nitrate supplementation can provide (1) compensation when NOS activity is inadequate, and (2) cardioprotective benefits beyond that provided by a healthy NOS system. In addition, it discusses how to obtain a safe and efficacious range of inorganic nitrate.

15N-labelled nitrite/nitrate tracer analysis by LC-MS/MS: Urinary and fecal excretion of nitrite/nitrate following oral administration to mice

Determination of the modulation of nitrite and nitrate levels in biological samples usually poses a major challenge, owing to their high background concentrations. To effectively investigate the variation of nitrite/nitrate in vivo, in this study, we developed a¹⁵N-labelled nitrite/nitrate tracer analysis using LC-MS/MS following the derivatization with 2,3-diaminonaphthalene. This method allows for the determination of ¹⁵N-labelled nitrite/nitrate as ¹⁵N-2,3-naphthotriazole (¹⁵N-NAT) that can efficiently differentiate newly introduced nitrite/nitrate from the background nitrite/nitrate in biological matrices. We also investigated the contribution of background ¹⁴N-NAT isotopomers to ¹⁵N-NAT, which has long been overlooked in the literature. Our results indicated that the contribution of background ¹⁴N-NAT isotopomers to ¹⁵N-NAT is significant. Such contribution is constant (~2.2% under positive ion mode and 1.1% under negative ion mode), and does not depend upon the concentration of ¹⁴N-NAT or the sample matrix measured. An equation has been therefore developed, for the first time, to correct the contribution of background ¹⁴N-NAT isotopomers to ¹⁵N-NAT. With the proposed ¹⁵N-labelled nitrite/nitrate tracer analysis, the amount and percentage distribution of ¹⁵NO₂^- and ¹⁵NO₃^-, both in urine and feces, after oral administration of ¹⁵N-labelled nitrite/nitrate are clearly demonstrated. The excretions of ¹⁵NO₂^- and ¹⁵NO₃^- were significantly increased with the increasing dose implying that the dietary nitrite/nitrate intake is an important source in urine/feces. The present method allows for the simple, reliable and accurate quantification of ¹⁵NO₂^- and ¹⁵NO₃^-, and it should also be useful to trace the biotransformation of nitrite and nitrate in vivo.

Knowledge and beliefs about dietary inorganic nitrate among UK-based nutrition professionals: Development and application of the KINDS online questionnaire

OBJECTIVES

To examine knowledge and beliefs about the biological roles of dietary inorganic nitrate in UK-based nutrition professionals, and to explore potential differences by participants' education level.

SETTING

An online questionnaire was administered to UK-based nutrition professionals, exploring knowledge and/or beliefs across five areas: (1) health and performance effects of nitrate; (2) current and recommended intake values for nitrate; (3) dietary sources of nitrate; (4) methods of evaluating nitrate intake and (5) nitrate metabolism.

PARTICIPANTS

One hundred and twenty-five nutrition professionals.

PRIMARY OUTCOME

Knowledge and beliefs about inorganic nitrate.

RESULTS

Most nutrition professionals taking part in the survey had previously heard of inorganic nitrate (71%) and perceived it to be primarily beneficial (51%). The majority believed that nitrate consumption can improve sports performance (59%) and reduce blood pressure (54%), but were unsure about effects on cognitive function (71%), kidney function (80%) and cancer risk (70%). Knowledge of dietary sources of nitrate and factors affecting its content in food were generally good (41%-79% of participants providing correct answers). However, most participants were unsure of the average population intake (65%) and the acceptable daily intake (64%) of nitrate. Most participants (65%) recognised at least one compound (ie, nitric oxide or nitrosamines) that is derived from dietary nitrate in the body. Knowledge of nitrate, quantified by a 23-point index created by summing correct responses, was greater in individuals with a PhD (p=0.01; median (IQR)=13 (9-17)) and tended to be better in respondents with a masters degree (p=0.054; 13 (8-15)) compared with undergraduate-level qualifications (10 (2-14)).

CONCLUSIONS

UK-based nutrition professionals demonstrated mixed knowledge about the physiology of dietary nitrate, which was better in participants with higher education. More efficient dissemination of current knowledge about inorganic nitrate and its effects on health to nutrition professionals will support them to make more informed recommendations about consumption of this compound.

Metabolic Trajectories Following Contrasting Prudent and Western Diets from Food Provisions: Identifying Robust Biomarkers of Short-Term Changes in Habitual Diet

A large body of evidence has linked unhealthy eating patterns with an alarming increase in obesity and chronic disease worldwide. However, existing methods of assessing dietary intake in nutritional epidemiology rely on food frequency questionnaires or dietary records that are prone to bias and selective reporting. Herein, metabolic phenotyping was performed on 42 healthy participants from the Diet and Gene Intervention (DIGEST) pilot study, a parallel two-arm randomized clinical trial that provided complete diets to all participants. Matching single-spot urine and fasting plasma specimens were collected at baseline, and then following two weeks of either a Prudent or Western diet with a weight-maintaining menu plan designed by a dietician. Targeted and nontargeted metabolite profiling was conducted using three complementary analytical platforms, where 80 plasma metabolites and 84 creatinine-normalized urinary metabolites were reliably measured (CV < 30%) in the majority of participants (>75%) after implementing a rigorous data workflow for metabolite authentication with stringent quality control. We classified a panel of metabolites with distinctive trajectories following two weeks of food provisions when using complementary univariate and multivariate statistical models. Unknown metabolites associated with contrasting dietary patterns were identified with high-resolution MS/MS, as well as co-elution after spiking with authentic standards if available. Overall, 3-methylhistidine and proline betaine concentrations increased in both plasma and urine samples after participants were assigned a Prudent diet (q < 0.05) with a corresponding decrease in the Western diet group. Similarly, creatinine-normalized urinary imidazole propionate, hydroxypipecolic acid, dihydroxybenzoic acid, and enterolactone glucuronide, as well as plasma ketoleucine and ketovaline increased with a Prudent diet (p < 0.05) after adjustments for age, sex, and BMI. In contrast, plasma myristic acid, linoelaidic acid, linoleic acid, α-linoleic acid, pentadecanoic acid, alanine, proline, carnitine, and deoxycarnitine, as well as urinary acesulfame K increased among participants following a Western diet. Most metabolites were also correlated (r > ± 0.30, p < 0.05) to changes in the average intake of specific nutrients from self-reported diet records reflecting good adherence to assigned food provisions. Our study revealed robust biomarkers sensitive to short-term changes in habitual diet, which is needed for accurate monitoring of healthy eating patterns in free-living populations, and evidence-based public health policies for chronic disease prevention.

Evaluation of Haptoglobin Genotype and Some Risk Factors of Cancer in Patients with Early Stage Esophageal Cancer

INTRODUCTION

Esophageal cancer is one of the most lethal gastrointestinal cancers that has a complex and diverse etiology, with several genetic and nutritional factors involved in its etiology. The purpose of this study was to investigate the type of haptoglobin genotype and its relationship with some nutritional and biochemical risk factors affecting the prevalence of esophageal cancer in patients with early stage esophageal cancer.

MATERIALS AND METHODS

In this study, 44 patients (20 males and 24 females) with early stage esophageal cancer and 44 healthy subjects, classified as control group, (19 males and 25 females) were selected. Haptoglobin (HP) genotype was determined employing PCR technique. Nutritional data were analyzed using standard food frequency questionnaire (FFQ) method. Serum levels of malondialdehyde (MDA), nitrate and nitrite were measured employing the colorimetric method. Serum levels of p53 protein were measured using the enzyme-linked immunosorbent assay (ELISA) technique.

RESULTS

The results of our study showed for the first time that HP1-1 genotype was the most prevalent genotype in esophageal cancer patients in Golestan province, Iran. HP2-2 genotype was the most frequent in the control group. Serum levels of MDA were significantly higher in the patients' group compared to the control group (P˂0.001). Weight and body mass index (BMI) were significantly lower in the patients' group than the control group (P<0.01). Food frequency analysis revealed that the consumption of fruits and vegetables in the patients' group was lower than that of the control group (P<0.05).

CONCLUSION

The results of our study showed for the first time that HP1-1 genotype is the dominant genotype in patients with esophageal cancer in Golestan province. As well, modification of nutritional pattern and consumption of high level of antioxidant compounds can be effective in reducing the prevalence of esophageal cancer in this region.

The role of inorganic nitrate and nitrite in cardiovascular disease risk factors: a systematic review and meta-analysis of human evidence

Context

Depleted nitric oxide levels in the human body play a major role in cardiovascular disease pathogenesis. Inorganic nitrate/nitrite (rich dietary sources include beetroot and spinach) can act as a nitric oxide donor because nitrate/nitrite can be metabolized to produce nitric oxide.

Objective

This review and meta-analysis sought to investigate the role of inorganic nitrate/nitrite in preventing or treating cardiovascular disease risk factors in humans.

Data Sources

Electronic databases, including Medline, Embase, Cumulative Index to Nursing and Allied Health Literature, Cochrane, and Scopus, were searched.

Data Extraction

Experimental trials examining the effect of oral inorganic nitrate/nitrite intake on cardiovascular disease risk factors were included for systematic analysis.

Results

Thirty-four studies were included for qualitative synthesis, 23 of which were eligible for meta-analysis. Included studies measured the following outcomes: blood pressure, endothelial function, arterial stiffness, platelet aggregation, and/or blood lipids. Inorganic nitrate intake was found to significantly reduce resting blood pressure (systolic blood pressure: -4.80 mmHg, P < 0.0001; diastolic blood pressure: -1.74 mmHg, P = 0.001), improve endothelial function (flow-mediated dilatation: 0.59%, P < 0.0001), reduce arterial stiffness (pulse wave velocity: -0.23 m/s, P < 0.0001; augmentation index: -2.1%, P = 0.05), and reduce platelet aggregation by 18.9% (P < 0.0001).

Conclusions

Inorganic nitrate consumption represents a simple strategy for targeting cardiovascular disease risk factors. Future studies investigating the long-term effects of inorganic nitrate on cardiovascular disease outcomes are warranted.

Nitric oxide and its derivatives in the cancer battlefield

Elevated levels of reactive nitrogen species, alteration in redox balance and deregulated redox signaling are common hallmarks of cancer progression and chemoresistance. However, depending on the cellular context, distinct reactive nitrogen species are also hypothesized to mediate cytotoxic activity and are thus used in anticancer therapies. We present here the dual face of nitric oxide and its derivatives in cancer biology. Main derivatives of nitric oxide, such as nitrogen dioxide and peroxynitrite cause cell death by inducing protein and lipid peroxidation and/or DNA damage. Moreover, they control the activity of important protein players within the pro- and anti-apoptotic signaling pathways. Thus, the control of intracellular reactive nitrogen species may become a sophisticated tool in anticancer strategies.

No longer beeting around the bush: a review of potential sex differences with dietary nitrate supplementation

Over the last decade there has been substantial interest in the health and athletic performance benefits associated with acute and chronic dietary nitrate (NO3–) supplementation. Dietary NO3–, commonly found in leafy green and root vegetables, undergoes sequential reduction to nitrite and nitric oxide (NO) via the enterosalivary circulation. Importantly, NO has been shown to elicit a number of biological effects ranging from blood pressure reduction to improved exercise economy and athletic performance. However, a common absence within biological research is the lack of female participants, which is often attributed to the added complexity of hormonal fluctuations throughout the menstrual cycle. Despite mounting evidence supporting significant anthropometric, metabolic, and physiological differences between the sexes, this problem extends to the field of dietary NO3– supplementation where women are underrepresented as research participants. This review examines the existing dietary NO3– supplementation research with regards to dietary NO3– pharmacokinetics, resting blood pressure, exercise economy and performance, and mechanisms of action. It also provides evidence and rationale for potential sex differences in response to dietary NO3– supplementation and future directions for this field of research.

Novelty Dietary NO3– supplementation has been shown to have positive impacts on health and athletic performance in generally male populations. However, women are underrepresented in dietary NO3– supplementation research. The present evidence suggests that sex differences exist in response to dietary NO3– supplementation and this review highlights avenues for future research.

Human skeletal muscle nitrate store: influence of dietary nitrate supplementation and exercise

Rodent skeletal muscle contains a large store of nitrate that can be augmented by the consumption of dietary nitrate. This muscle nitrate reservoir has been found to be an important source of nitrite and nitric oxide (NO) via its reduction by tissue xanthine oxidoreductase. To explore if this pathway is also active in human skeletal muscle during exercise, and if it is sensitive to local nitrate availability, we assessed exercise-induced changes in muscle nitrate and nitrite concentrations in young healthy humans, under baseline conditions and following dietary nitrate consumption. We found that baseline nitrate and nitrite concentrations were far higher in muscle than in plasma (~4-fold and ~29-fold, respectively), and that the consumption of a single bolus of dietary nitrate (12.8 mmol) significantly elevated nitrate concentration in both plasma (~19-fold) and muscle (~5-fold). Consistent with these observations, and with previous suggestions of active muscle nitrate transport, we present western blot data to show significant expression of the active nitrate/nitrite transporter sialin in human skeletal muscle. Furthermore, we report an exercise-induced reduction in human muscle nitrate concentration (by ~39%), but only in the presence of an increased muscle nitrate store. Our results indicate that human skeletal muscle nitrate stores are sensitive to dietary nitrate intake and may contribute to NO generation during exercise. Together, these findings suggest that skeletal muscle plays an important role in the transport, storage and metabolism of nitrate in humans.

A novel organic mineral complex prevented high fat diet-induced hyperglycemia, endotoxemia, liver injury and endothelial dysfunction in young male Sprague-Dawley rats

The prevalence of metabolic syndrome (MetSyn) has risen 35% since 2012 and over two-thirds of Americans exhibit features characterizing this condition (obesity, dyslipidemia, hyperglycemia, insulin resistance and/or endothelial dysfunction). The aim of this study was to evaluate the effects of a novel dietary supplemental organic mineral complex (OMC) on these risk factors in a rodent model of MetSyn. Six-week old male Sprague-Dawley rats were fed either standard chow or a high-fat diet (HFD) composed of 60% kcal from fat for 10 weeks. Rats were also treated with OMC in their drinking water at either 0 mg/mL (control), 0.6 mg/mL, or 3.0 mg/mL. The HFD-treated rats exhibited significantly increased body mass (p<0.05), epididymal fat pad mass (p<0.001), waist circumference (p = 0.010), in addition to elevations in plasma endotoxins (p<0.001), ALT activity (p<0.001), fasting serum glucose (p = 0.025) and insulin concentrations (p = 0.009). OMC did not affect body weight or adiposity induced by the HFD. At the higher dose OMC significantly blunted HFD-induced hyperglycemia (p = 0.021), whereas both low and high doses of OMC prevented HFD-induced endotoxemia (p = 0.002 and <0.001, respectively) and hepatocyte injury (ALT activity, p<0.01). Despite evidence of oxidative stress (elevated urinary H2O2 p = 0.032) in HFD-fed rats, OMC exhibited no demonstrable antioxidative effect. Consistent with prior studies, mesenteric arteries from HFD rats had more uncoupled eNOS (p = 0.006) and iNOS protein expression (p = 0.027) in addition to impaired endothelium-dependent vasodilation that was abrogated by the high dose of OMC (p<0.05). This effect of OMC may be attributed to the high nitrate content of the supplement. These findings suggest that the OMC supplement, particularly at the higher dose, ameliorated several risk factors associated with MetSyn via a non-antioxidant-dependent mechanism.

Effects of almond, dried grape and dried cranberry consumption on endurance exercise performance, recovery and psychomotor speed: protocol of a randomised controlled trial

Background

Foods rich in nutrients, such as nitrate, nitrite, L-arginine and polyphenols, can promote the synthesis of nitric oxide (NO), which may induce ergogenic effects on endurance exercise performance. Thus, consuming foods rich in these components, such as almonds, dried grapes and dried cranberries (AGC), may improve athletic performance. Additionally, the antioxidant properties of these foods may reduce oxidative damage induced by intense exercise, thus improving recovery and reducing fatigue from strenuous physical training. Improvements in NO synthesis may also promote cerebral blood flow, which may improve cognitive function.

Methods and analysis

Ninety-six trained male cyclists or triathletes will be randomised to consume ~2550 kJ of either a mixture of AGC or a comparator snack food (oat bar) for 4 weeks during an overreaching endurance training protocol comprised of a 2-week heavy training phase, followed by a 2-week taper. The primary outcome is endurance exercise performance (5 min time-trial performance) and secondary outcomes include markers of NO synthesis (plasma and urinary nitrites and nitrates), muscle damage (serum creatine kinase and lactate dehydrogenase), oxidative stress (F2-isoprostanes), endurance exercise function (exercise efficiency, submaximal oxygen consumption and substrate utilisation), markers of internal training load (subjective well-being, rating of perceived exertion, maximal rate of heart rate increase and peak heart rate) and psychomotor speed (choice reaction time).

Conclusion

This study will evaluate whether consuming AGC improves endurance exercise performance, recovery and psychomotor speed across an endurance training programme, and evaluate the mechanisms responsible for any improvement.

Trial registration number

ACTRN12618000360213.

Reciprocal regulation of sulfite oxidation and nitrite reduction by mitochondrial sulfite oxidase

The oxygen-independent nitrate-nitrite-nitric oxide (NO) pathway is considered as a substantial source of NO in mammals. Dietary nitrate/nitrite are distributed throughout the body and reduced to NO by the action of various enzymes. The intermembrane spaced (IMS), molybdenum cofactor-dependent sulfite oxidase (SO) was shown to catalyze such a nitrite reduction. In this study we asked whether the primary function of SO - sulfite oxidation - and its novel function - nitrite reduction - impact each other. First, we utilized benzyl viologen as artificial electron donor to investigate steady state NO synthesis by SO and found fast (k_cat = 14 s^-1) nitrite reduction of SO full-length and its isolated molybdenum domain at pH 6.5. Next, we determined the impact of nitrite on pre-steady state kinetics in SO catalysis and identified nitrite as a pH-dependent inhibitor of SO reductive and oxidative half reaction. Finally, we report on the time-dependent formation of the paramagnetic Mo(V) species following nitrite reduction and demonstrate that sulfite inhibits nitrite reduction. In conclusion, we propose a pH-dependent reciprocal regulation of sulfite oxidation and nitrite reduction by each substrate, thus facilitating quick responses to hypoxia induced changes in the IMS, which may function in protecting the cell from reactive oxygen species production.

Effects of dietary nitrate on inflammation and immune function, and implications for cardiovascular health

Inorganic dietary nitrate, found abundantly in green leafy and some root vegetables, elicits several beneficial physiological effects, including a reduction in blood pressure and improvements in blood flow through nitrate-nitrite-nitric oxide signaling. Recent animal and human studies have shown that dietary nitrate and nitrite also modulate inflammatory processes and immune cell function and phenotypes. Chronic low-grade inflammation and immune dysfunction play a critical role in cardiovascular disease. This review outlines the current evidence on the efficacy of nitrate-rich plant foods and other sources of dietary nitrate and nitrite to counteract inflammation and promote homeostasis of the immune and vascular systems. The data from these studies suggest that immune cells and immune-vasculature interactions are important targets for dietary interventions aimed at improving, preserving, or restoring cardiovascular health.

Next Generation Sequencing Discoveries of the Nitrate-Responsive Oral Microbiome and Its Effect on Vascular Responses

Cardiovascular disease is a worldwide human condition which has multiple underlying contributing factors: one of these is long-term increased blood pressure—hypertension. Nitric oxide (NO) is a small nitrogenous radical species that has a number of physiological functions including vasodilation. It can be produced enzymatically through host nitric oxide synthases and by an alternative nitrate–nitrite–NO pathway from ingested inorganic nitrate. It was discovered that this route relies on the ability of the oral microbiota to reduce nitrate to nitrite and NO. Next generation sequencing has been used over the past two decades to gain deeper insight into the microbes involved, their location and the effect of their removal from the oral cavity. This review article presents this research and comments briefly on future directions.

Uncured-Labeled Meat Products Produced Using Plant-Derived Nitrates and Nitrites: Chemistry, Safety, and Regulatory Considerations

Consumers often malign conventional curing agents while concomitantly accepting the natural forms of the same constituents in numerous food products. This paradox ostensibly exceeds all other food-related controversies to date and likely contributes to the rapid expansion of meat products that utilize natural nitrate derivatives. While there is high demand for these products, a fundamental lack of understanding regarding the safety and chemical implications of curing agents, whether derived from synthetic or natural sources, continues to persist. This manuscript elucidates the variations among curing preparations with particular emphasis pertaining to the associated safety, chemical, and regulatory ramifications encompassing these product categories.

Nitrate and Nitrites in Foods: Worldwide Regional Distribution in View of Their Risks and Benefits

Nitrate and nitrite ions are used as food additives to inhibit the growth of microorganisms in cured and processed meats. Vegetables contain significant quantities of nitrate and nitrite. Actually, the vast majority of consumed nitrate and nitrite comes from natural vegetables and fruits rather than food additives. For years, the cancer risks of these two ions have been discussed, since they potentially convert into the carcinogenic nitrosamines. However, recently, these two ions have been considered essential nutrients which promote nitric oxide production and consequently help cardiovascular health. It seems that the role of these two ions in our diet is important now from a different point of view. In this review, the nitrate and nitrite contents of food products from different countries are displayed globally in order to reinterpret the risks/benefits of our consumption quotations. This review article is based on Science Citation Index (SCI) articles reported between 2008 and 2018.

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.

Dietary Nitrate and Physical Performance

Nitric oxide (NO) plays a plethora of important roles in the human body. Insufficient production of NO (for example, during older age and in various disease conditions) can adversely impact health and physical performance. In addition to its endogenous production through the oxidation of l-arginine, NO can be formed nonenzymatically via the reduction of nitrate and nitrite, and the storage of these anions can be augmented by the consumption of nitrate-rich foodstuffs such as green leafy vegetables. Recent studies indicate that dietary nitrate supplementation, administered most commonly in the form of beetroot juice, can ( a) improve muscle efficiency by reducing the O₂ cost of submaximal exercise and thereby improve endurance exercise performance and ( b) enhance skeletal muscle contractile function and thereby improve muscle power and sprint exercise performance. This review describes the physiological mechanisms potentially responsible for these effects, outlines the circumstances in which ergogenic effects are most likely to be evident, and discusses the effects of dietary nitrate supplementation on physical performance in a range of human populations.

Phytochemicals, antioxidant activity and hepatoprotective effect of ginger (Zingiber officinale) on diethylnitrosamine toxicity in rats

Context: Chronic liver damage has serious medical consequences. Objective: To investigate the hepatoprotective effect of dry Zingiber officinale (ginger) and its essential (volatile) oil against diethylnitrosamine (DEN) toxicity in rats. Materials and methods: Phenols and flavonoids components were characterized in dry ginger using HPLC-UV instrument while ginger essential oil (E.O.) was investigated via GC-MS technique. Antioxidant activity was determined in vitro. In rat model, ginger was administrated for 2 months. Lipid profile, antioxidant biomarkers, liver functions and histopathology were assessed. Results: Chlorogenic acid (63.85 ppm) and hesperidin (156.91 ppm) are among the major phenolic and flavonoid constituents in dry ginger. Curcumene (15.21%) and linalool (13.47%) represent the main E.O. constituents. In rats treated with ginger E.O., a significant elevation in serum HDL (31.14%) was accompanied by a decrease in LDL (55.14%). A significant decrease in serum ALT and ALP was reported (56.85% and 53.84%, respectively). Serum GSH-Px activity has significantly increased 75.06%. Meanwhile, E.O. showed anticancer potential against HepG2 cell line (IC50 = 40 µg/mL). Liver histopathological examinations confirmed the protective effect against abnormalities. Conclusion: Ginger was able to reduce the severity of DEN-cytotoxicity in rats, which suggests a novel antioxidant role originating from this medicinal plant.

Effect of spironolactone for 1 yr on endothelial function and vascular inflammation biomarkers in renal transplant recipients

Kidney transplantation is associated with increased cardiovascular risk. Endothelial dysfunction and vascular inflammation contribute to negative outcome. In experimental models, mineralocorticoid receptor antagonists improved endothelial function and reduced inflammation. The present study tested the hypothesis that the mineralocorticoid receptor antagonist spironolactone improves endothelial function and reduces vascular inflammation in renal transplant patients. Eighty prevalent renal transplant patients from an ongoing, double-blind randomized placebo-controlled trial were included. Paired plasma samples before and after 1 yr of treatment (n = 39 in the spironolactone-treated group and 41 in the placebo-treated group) were used to determine markers of endothelial dysfunction (nitrite, nitrate, cGMP, arginine, citrulline, ornithine, asymmetric dimethylarginine, symmetric dimethylarginine, N^G-monomethyl-l-arginine, von Willebrand factor, tissue-type plasminogen activator antigen, and plasminogen activator inhibitor 1 antigen) and markers of inflammation (intercellular adhesion molecule, vascular adhesion molecule, high-sensitivity C-reactive protein, and serum amyloid protein A). The median time since the transplantation was 4.6 (0.12-22.3) yr in the spironolactone-treated group and 2.1 (0.17-13.9) yr in the placebo-treated group (P > 0.05). Spironolactone increased plasma aldosterone (P < 0.001) and K⁺ (P < 0.001). Blood pressure did not change significantly. No significant differences were detected between groups in any of the measured markers of endothelial dysfunction or inflammation except in the subgroup analysis of patients with diabetes, where spironolactone decreased nitrite compared with placebo. In this study, mineralocorticoid receptor antagonism did not improve biomarkers of endothelial dysfunction or vascular inflammation in prevalent renal transplant patients. Further studies are needed to evaluate the potential beneficial effect of early or late mineralocorticoid receptor antagonism on vascular outcomes in renal transplant patients.

NOx- anion recognition by bimetallic cryptates: selectivity for nitrite over nitrate

Nitrate and nitrite anions have multifaceted impacts on the environment and human health. We herein report selective recognition of nitrite over nitrate anion inside the cavity of bimetallic azacryptates having p-xylyl spacers. This work reveals a number of binding interactions which play pivotal roles in nitrite anion recognition by rigid metal cryptates.

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 Supplementation Improves Exercise Tolerance by Reducing Muscle Fatigue and Perceptual Responses

The present study was designed to provide further insight into the mechanistic basis for the improved exercise tolerance following dietary nitrate supplementation. In a randomized, double-blind, crossover design, twelve recreationally active males completed a dynamic time-to-exhaustion test of the knee extensors after 5 days of consuming both nitrate-rich (NITRATE) and nitrate-depleted beetroot juice (PLACEBO). Participants who improved their time-to-exhaustion following NITRATE performed a time-matched trial corresponding to the PLACEBO exercise duration with another 5 days of dietary nitrate supplementation. This procedure was performed to obtain time-matched exercise trials with (NITRATE_tm) and without dietary nitrate supplementation (PLACEBO). Neuromuscular tests were performed before and after each time-matched condition. Muscle fatigue was quantified as percentage change in maximal voluntary torque from pre- to post-exercise (ΔMVT). Changes in voluntary activation (ΔVA) and quadriceps twitch torque (ΔPS100) were used to quantify central and peripheral factors of muscle fatigue, respectively. Muscle oxygen saturation, quadriceps muscle activity as well as perceptual data (i.e., perception of effort and leg muscle pain) were recorded during exercise. Time-to-exhaustion was improved with NITRATE (12:41 ± 07:18 min) compared to PLACEBO (09:03 ± 04:18 min; P = 0.010). NITRATE_tm resulted in both lower ΔMVT and ΔPS100 compared to PLACEBO (P = 0.002; P = 0.001, respectively). ΔVA was not different between conditions (P = 0.308). NITRATE_tm resulted in reduced perception of effort and leg muscle pain. Our findings extend the mechanistic basis for the improved exercise tolerance by showing that dietary nitrate supplementation (i) attenuated the development of muscle fatigue by reducing the exercise-induced impairments in contractile muscle function; and (ii) lowered the perception of both effort and leg muscle pain during exercise.

Determination of the [15N]-Nitrate/[14N]-Nitrate Ratio in Plant Feeding Studies by GC⁻MS

Feeding experiments with stable isotopes are helpful tools for investigation of metabolic fluxes and biochemical pathways. For assessing nitrogen metabolism, the heavier nitrogen isotope, [¹⁵N], has been frequently used. In plants, it is usually applied in form of [¹⁵N]-nitrate, which is assimilated mainly in leaves. Thus, methods for quantification of the [¹⁵N]-nitrate/[¹⁴N]-nitrate ratio in leaves are useful for the planning and evaluation of feeding and pulse–chase experiments. Here we describe a simple and sensitive method for determining the [¹⁵N]-nitrate to [¹⁴N]-nitrate ratio in leaves. Leaf discs (8 mm diameter, approximately 10 mg fresh weight) were sufficient for analysis, allowing a single leaf to be sampled multiple times. Nitrate was extracted with hot water and derivatized with mesitylene in the presence of sulfuric acid to nitromesitylene. The derivatization product was analyzed by gas chromatography–mass spectrometry with electron ionization. Separation of the derivatized samples required only 6 min. The method shows excellent repeatability with intraday and interday standard deviations of less than 0.9 mol%. Using the method, we show that [¹⁵N]-nitrate declines in leaves of hydroponically grown Crassocephalum crepidioides, an African orphan crop, with a biological half-life of 4.5 days after transfer to medium containing [¹⁴N]-nitrate as the sole nitrogen source.

Montmorency cherry supplement does not affect aerobic exercise performance in healthy men

Aim: To determine the effects of short-term Montmorency cherry (MC) supplementation upon exercise performance, total blood nitrate levels, muscle oxygenation, and slow-component [Formula: see text]O₂ kinetics. Methods: Twelve healthy male participants ingested a MC or placebo (PL) supplement in a randomized cross-over fashion over a six day period then cycled at a power output achieved at 70% of [Formula: see text]O₂ peak for a maximum of 30 minutes or until exhaustion. Near-Infrared Spectroscopy sensors were used to determine muscle oxygenation. Blood was collected one hour post-supplement consumption on day one, day six, and one hour post-exercise. Results: All results are presented as mean ± SEM. Blood nitrate (μM/L) levels were not different one hour post-ingestion (MC = 8.30 ± 2.15, PL = 8.18 ± 1.86), following six days of supplementation (MC = 9.14 ± 1.89, PL = 7.24 ± 1.75) or one hour post-exercise (MC = 9.63 ± 1.61, PL = 7.97 ± 1.92) for treatment F = 0.26, p = 0.62; for time F = 0.45, p = 0.64; or treatment by time interaction F = 2.28, p = 0.13. Muscle oxygenation was not different between treatments for the right or left vastus lateralis, F = 0.68, p = 0.81 nor was time to respiratory compensation point (minutes) (MC = 18.40 ± 1.48, PL = 17.16 ± 1.78) F = 0.52, p = 0.60. MC supplement ingestion does not alter blood nitrate levels. Conclusion: Short-term MC ingestion does not increase muscle oxygenation during cycling exercise nor does it change slow-component [Formula: see text]O₂ kinetics.

Impact of Excessive Nitrogen Fertilization on the Biochemical Quality, Phenolic Compounds, and Antioxidant Power of Sesamum indicum L Seeds

Nitrogen is an essential nutrient for plants life cycle. However, the excessive use of this element causes serious problems in agriculture. This can disrupt the development of many important plants. Sesamum indicum or sesame represents one of the most economically important and ancient oil crops in the world. In fact, its seeds are used for many biological activities. The aim of the present study is to evaluate the effect of high levels of nitrogen on some primary and secondary metabolites and the antioxidant activity under different levels of N supply. Results analysis of our investigation showed that the excessive nitrogen supply had a serious effect on the quality of sesame seeds. In fact, N fertilizer promoted the accumulation of proteins until 57.16%, in detriment of oil and sugars that decreased with 49.43% and 16.27%, respectively. Also, total phenolic, flavonoids content, and antioxidant activity showed a significant decrease.

Circulating markers of nitric oxide homeostasis and cardiometabolic diseases: insights from population-based studies

Emerging data suggest that impaired nitric oxide (NO) homeostasis has a key role in development of cardiometabolic disorders. The association between circulating levels of NO metabolites, i.e. nitrate and nitrite (NOx), and risk of chronic diseases has not yet been fully clarified. This work aims to address epidemiologic aspects of NO metabolism and discusses different physiologic and pathophysiologic conditions influencing circulating NOx. Further, cross-sectional associations of serum NOx with metabolic disorders are described and along the way, potential short-term and long-term power of serum NOx for predicting cardiometabolic outcomes are reviewed. Results from population-based studies show that circulating NOx is affected by aging, smoking habits, pregnancy, menopause status, thyroid hormones, and various pathologic conditions including type 2 diabetes, insulin resistance, hypertension, and renal dysfunction. Lifestyle factors, especially dietary habits, but also smoking habits and the degree of physical activity influence NO homeostasis and the circulating levels of NOx. Elevated serum NOx, due to increased iNOS activity, is associated with increased incidence of metabolic syndrome, different obesity phenotypes, and cardiovascular events.