Effects Of Nitrate Supplementation Research Articles

A preventative role of nitrate for hypoxia-induced intestinal injury

BackgroundStudying effective interventions for hypoxia-induced injury is crucial, particularly in high-altitude areas. Symptoms stemming from intestinal injuries have a significant impact on the health of individuals transitioning from plains to plateau regions. This research explores the effects and mechanisms of nitrate supplementation in preventing hypoxia-induced intestinal injury. MethodsA hypoxia survival mouse model was established using 7% O2 conditions. The intervention with 4 mM sodium nitrate (NaNO3) in drinking water commenced 7 days prior to hypoxia exposure. Weight monitoring, hematoxylin and eosin (HE) staining, transmission electron microscopy (TEM), and intestinal permeability assays were employed for physiological, histological, and functional analyses. Quantitative PCR (qPCR), Western blot, and immunofluorescence were utilized to analyze the levels of tight junction (TJ) proteins and hypoxia-inducible factor 1α (Hif 1α). RNA sequencing (RNA-seq) identified nitrate's target, and chromatin immunoprecipitation (ChIP) verified the transcriptional impact of Hif 1α on TJ proteins. Villin-cre mice infected with AAV9-FLEX-EGFP-Hif 1α were used for mechanism validation. ResultsThe results demonstrated that nitrate supplementation significantly alleviated small intestinal epithelial cell necrosis, intestinal permeability, disruption of TJs, and weight loss under hypoxia. Moreover, the nitrate-triggered enhancement of TJs is mediated by Hif 1α nuclear translocation and its subsequent transcriptional function. The effect of nitrate supplementation on TJs was largely attributed to the stimulation of the EGFR/PI3K/AKT/mTOR/Hif 1α signaling pathways. ConclusionNitrate serves as a novel approach in preventing hypoxia-induced intestinal injury, acting through Hif 1α activation to promote the transcription of TJ proteins. Furthermore, our study provides new and compelling evidence for the protective effects of nitrate in hypoxic conditions, especially at high altitudes.

The Effects of Nitrate Supplementation on Performance as a Function of Habitual Dietary Intake of Nitrates: A Randomized Controlled Trial of Elite Football Players.

Nitrates are an effective ergogenic supplement; however, the effects of nitrate supplements based on habitual dietary nitrate intake through diet alone are not well understood. We aimed to assess this in a group of 15 highly trained football players from Slovenian football's First Division. Participants underwent two separate Cooper performance tests either with nitrate supplementation (400 mg nitrates) or placebo while having their nutrition assessed for nitrate intake, as well as energy and macronutrient intake. Nitrate supplementation had a statistically significant positive effect on performance if baseline dietary nitrate intake was below 300 mg (p = 0.0104) in both the placebo and intervention groups. No effects of nitrate supplementation when baseline dietary nitrate intake was higher than 300 mg in the placebo group could be concluded due to the small sample size. Nitrate supplementation did not have a significant effect on perceived exertion. The daily nitrate intake of the participants was measured at 165 mg, with the majority of nitrates coming from nitrate-rich vegetables.

Effect of nitrate supplementation, dietary protein supply, and genetic yield index on performance, methane emission, and nitrogen efficiency in dairy cows

The objective was to investigate the effect of nonprotein nitrogen source, dietary protein supply, and genetic yield index on methane emission, N metabolism, and ruminal fermentation in dairy cows. Forty-eight Danish Holstein dairy cows (24 primiparous cows and 24 multiparous cows) were used in a 6 × 4 incomplete Latin square design with 4 periods of 21-d duration. Cows were fed ad libitum with the following 6 experimental diets: diets with low, medium, or high rumen degradable protein (RDP):rumen undegradable protein (RUP) ratio (manipulated by changing the proportion of corn meal, corn gluten meal, and corn gluten feed) combined with either urea or nitrate (10 g NO3-/kg of dry matter) as nonprotein nitrogen source. Samples of ruminal fluid and feces were collected from multiparous cows, and total-tract nutrient digestibility was estimated using TiO2 as flow marker. Milk samples were collected from all 48 cows. Gas emission (CH4, CO2, and H2) was measured by 4 GreenFeed units. We observed no significant interaction between dietary RDP:RUP ratio and nitrate supplementation, and between nitrate supplementation and genetic yield index on CH4 emission (production, yield, intensity). As dietary RDP:RUP ratio increased, intake of crude protein, RDP, and neutral detergent fiber and total-tract digestibility of crude protein linearly increased, and RUP intake linearly decreased. Yield of milk, energy-corrected milk, and milk protein and lactose linearly decreased, whereas milk fat and milk urea nitrogen concentrations linearly increased as dietary RDP:RUP ratio increased. The increase in dietary RDP:RUP ratio resulted in a linear increase in the excretion of total purine derivatives and N in urine, but a linear decrease in N efficiency (milk N in % of N intake). Nitrate supplementation reduced dry matter intake (DMI) and increased total-tract organic matter digestibility compared with urea supplementation. Nitrate supplementation resulted in a greater reduction in DMI and daily CH4 production and a greater increase in daily H2 production in multiparous cows compared with primiparous cows. Nitrate supplementation also showed a greater reduction in milk protein and lactose yield in multiparous cows than in primiparous cows. Milk protein and lactose concentrations were lower for cows receiving nitrate diets compared with cows receiving urea diets. Nitrate supplementation reduced urinary purine derivatives excretion from the rumen, whereas N efficiency tended to increase. Nitrate supplementation reduced proportion of acetate and propionate in ruminal volatile fatty acids. In conclusion, no interaction was observed between dietary RDP:RUP ratio and nitrate supplementation, and no interaction between nitrate supplementation and genetic yield index on CH4 emission (production, yield, intensity) was noted. Nitrate supplementation resulted in a greater reduction in DMI and CH4 production, and a greater increase in H2 production in multiparous cows than in primiparous cows. As the dietary RDP:RUP ratio increased, CH4 emission was unaffected and RDP intake increased, but RUP intake and milk yield decreased. Genetic yield index did not affect CH4 production, yield, or intensity.

Effect of nitrate supplementation on skeletal muscle motor unit activity during isometric blood flow restriction exercise

BackgroundNitrate (NO3−) supplementation has been reported to lower motor unit (MU) firing rate (MUFR) during dynamic resistance exercise; however, its impact on MU activity during isometric and ischemic exercise is unknown.PurposeTo assess the effect of NO3− supplementation on knee extensor MU activities during brief isometric contractions and a 3 min sustained contraction with blood flow restriction (BFR).MethodsSixteen healthy active young adults (six females) completed two trials in a randomized, double-blind, crossover design. Trials were preceded by 5 days of either NO3− (NIT) or placebo (PLA) supplementation. Intramuscular electromyography was used to determine the M. vastus lateralis MU potential (MUP) size, MUFR and near fibre (NF) jiggle (a measure of neuromuscular stability) during brief (20 s) isometric contractions at 25% maximal strength and throughout a 3 min sustained BFR isometric contraction.ResultsPlasma nitrite (NO2−) concentration was elevated after NIT compared to PLA (475 ± 93 vs. 198 ± 46 nmol L−1, p < 0.001). While changes in MUP area, NF jiggle and MUFR were similar between NIT and PLA trials (all p > 0.05), MUP duration was shorter with NIT compared to PLA during brief isometric contractions and the sustained ischemic contraction (p < 0.01). In addition, mean MUP duration, MUP area and NF jiggle increased, and MUFR decreased over the 3 min sustained BFR isometric contraction for both conditions (all p < 0.05).ConclusionsThese findings provide insight into the effect of NO3− supplementation on MUP properties and reveal faster MUP duration after short-term NO3− supplementation which may have positive implications for skeletal muscle contractile performance.

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

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

Nitrate-rich beetroot juice ingestion reduces skeletal muscle O2 uptake and blood flow during exercise in sedentary men.

Dietary nitrate supplementation has been shown to reduce pulmonary O2 uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this, eight healthy young male sedentary subjects were assigned in a randomized, double-blind, crossover design to receive nitrate-rich beetroot juice (NO3, 9mmol) and placebo (PLA) 2.5h prior to the completion of a double-step knee-extensor exercise protocol that included a transition from unloaded to moderate-intensity exercise (MOD) followed immediately by a transition to intense exercise (HIGH). Compared with PLA, NO3 increased plasma levels of nitrate and nitrite. During MOD, leg and leg blood flow (LBF) were reduced to a similar extent (∼9%-15%) in NO3. During HIGH, leg was reduced by ∼6%-10% and LBF by ∼5%-9% (did not reach significance) in NO3. Leg kinetics was markedly faster in the transition from passive to MOD compared with the transition from MOD to HIGH both in NO3 and PLA with no difference between PLA and NO3. In NO3, a reduction in nitrate and nitrite concentration was detected between arterial and venous samples. No difference in the time to exhaustion was observed between conditions. In conclusion, elevation of plasma nitrate and nitrate reduces leg skeletal muscle and blood flow during exercise. However, nitrate supplementation does not enhance muscle kinetics during exercise, nor does it improve time to exhaustion when exercising with a small muscle mass. KEY POINTS: Dietary nitrate supplementation has been shown to reduce systemic O2 uptake during exercise and improve exercise performance. The effects of nitrate supplementation on local metabolism and blood flow regulation in contracting human skeletal muscle remain unclear. By using leg exercise engaging a small muscle mass, we show that O2 uptake and blood flow are similarly reduced in contracting skeletal muscle of humans during exercise. Despite slower kinetics in the transition from moderate to intense exercise, no effects of nitrate supplementation were observed for kinetics and time to exhaustion. Nitrate and nitrite concentrations are reduced across the exercising leg, suggesting that these ions are extracted from the arterial blood by contracting skeletal muscle.

Effects of Nitrate Supplementation on Exercise Performance in Humans: A Narrative Review.

Nitrates have become increasingly popular for their potential role as an ergogenic aid. The purpose of this article was to review the current scientific evidence of nitrate supplementation on human performance. The current recommendation of nitrate supplementation is discussed, as well as possible health complications associated with nitrate intake for athletes, and dietary strategies of covering nitrate needs through sufficient intake of nitrate-rich foods alone are presented. Pubmed, Scopus, and Web of Science were searched for articles on the effects of nitrate supplementation in humans. Nitrates are an effective ergogenic aid when taken acutely or chronically in the range of ~5–16.8 mmol (~300–1041 mg) 2–3 h before exercise and primarily in the case of exercise duration of ~10–17 min in less trained individuals (VO2max < 65 mL/kg/min). Nitrate needs are most likely meet by ingesting approximately 250–500 g of leafy and root vegetables per day; however, dietary supplements might represent a more convenient and accurate way of covering an athlete’s nitrate needs. Athletes should refrain from mouthwash usage when nitrate supplementation benefits are desired. Future research should focus on the potential beneficial effects of nitrate supplementation on brain function, possible negative impacts of chronic nitrate supplementation through different nitrate sources, and the effectiveness of nitrate supplementation on strength and high-intensity intermittent exercise.

Effect Of Nitrate Supplementation On Motor Unit Functions In Healthy Active Adults

Effect Of Nitrate Supplementation On Motor Unit Functions In Healthy Active Adults

Cutaneous reactive hyperaemia is unaltered by dietary nitrate supplementation in healthy humans.

The purpose of this study was to determine whether nitrate supplementation augments cutaneous reactive hyperaemia. Seven participants were tested pre- and postnitrate supplementation (25ml beetroot juice); participants consumed one shot per day for 3days. Participants were instrumented with two microdialysis fibres: control (Ringer's solution) and NO synthase inhibition (20mM L-NAME). Skin blood flow was measured via laser-Doppler flowmetry (LDF). A blood pressure cuff was placed on the experimental arm and inflated to 250 mmHg for 5mins to occlude arterial inflow. The cuff was released, and the resultant reactive hyperaemia was measured. Blood pressure was continuously measured via plethysmography from a finger on the non-experimental arm. Cutaneous vascular conductance was calculated (LDF/MAP) and normalized to maximal vasodilatation (%CVCmax ). Only diastolic blood pressure was reduced following nitrate supplementation (71±2 vs. 66±1mmHg; P<0·05). There was no effect of nitrate supplementation on peak reactive hyperaemia at control (Pre: 52±3 vs. Post: 57±2%CVCmax ) or L-NAME (Pre: 52±2 vs. Post: 59±4%CVCmax ) sites. There was no effect of nitrate supplementation on total reactive hyperaemia at either control (Pre: 4197±943 vs. Post: 4523±1040%CVCmax * sec) or L-NAME (Pre: 5108±997 vs. Post: 5694±1002%CVCmax * sec) sites. These data suggest cutaneous reactive hyperaemia is unaffected by dietary nitrate supplementation in healthy humans.

The Effect of Nitrate Supplementation on Cycling Performance in the Heat in Well-Trained Cyclists.

To determine the effect of [Formula: see text] consumption on measures of perception, thermoregulation, and cycling performance in hot conditions. In a randomized, double-blind, crossover design, 8 well-trained cyclists (mean ± SD age 25 ± 8y, [Formula: see text] peak 64 ± 5mL · kg-1 · min-1) performed 2 separate trials in hot (35°C, 60% relative humidity) environments, having ingested either 140 mL [Formula: see text]-rich beetroot juice ∼8mmol [Formula: see text] (NIT) or placebo (PLA) daily for 3 d with a 7-d washout period separating trials. Trials consisted of 2 × 10-min bouts at 40% and 60% peak power output (PPO) to determine physiological and perceptual responses to the heat, followed by a 4-km cycling time trial. Basal [nitrite] was substantially elevated in NIT (2.70 ± 0.98 µM) vs PLA (1.10 ± 0.61 µM), resulting in a most likely (ES = 1.58 ± 0.93) increase after 3 d. There was a very likely trivial increase in rectal temperature in NIT at 40% (PLA 37.4°C ± 0.2°C vs NIT 37.5°C ± 0.3°C, 0.1°C ± 0.2°C) and 60% (PLA 37.8°C ± 0.2°C vs NIT 37.9°C ± 0.3°C, 0.1°C ± 0.2°C) PPO. Cycling performance was similar between trials (PLA 336 ± 45W vs NIT 337 ± 50W, CV ± 95%CL; 0.2% ± 2.5%). Outcomes for heart rate and perceptual measures were unclear across the majority of time points. Three days of [Formula: see text] supplementation resulted in small increases in rectal temperature during low- to moderate-intensity exercise, but this did not appear to influence 4-km cycling time-trial performance in hot climates.

Effects of nitrate supplementation in trained and untrained muscle are modest with initial high plasma nitrite levels.

Nitrate (NO3-) supplementation resulting in higher plasma nitrite (NO2-) is reported to lower resting mean arterial blood pressure (MAP) and oxygen uptake (VO2 ) during submaximal exercise in non-athletic populations, whereas effects in general are absent in endurance-trained individuals. To test whether physiologic effects of NO3- supplementation depend on local muscular training status or cardiovascular fitness, male endurance-trained cyclists (CYC, n=9, VO2 -max: 64±3mL/min/kg; mean±SD) and recreational active subjects serving as a control group (CON, n=8, 46±3mL/min/kg), acutely consumed nitrate-rich beetroot juice ([NO3-] ~9mmol) (NIT) or placebo (PLA) with assessment of resting MAP and energy expenditure during moderate intensity (~50% VO2 -max) and incremental leg cycling (LEG-ex) and arm-cranking exercise (ARM-ex). NIT increased (P<.001) resting plasma NO3- by ~1200% relative to PLA. Plasma NO2- increased ~25% (P<.01) with a significant change only in CYC. LEG-ex VO2 (~2.60L/min), ARM-ex VO2 (~1.14L/min), and resting MAP (~87mm Hg) remained unchanged for CYC, and similarly for CON, no changes were observed for LEG-ex VO2 (~2.03L/min), ARM-ex VO2 (~1.06L/min), or resting MAP (~85mm Hg). VO2 -max was not affected by supplementation, but incremental test peak power was higher (P<.05) in LEG-ex for CYC in NIT relative to PLA (418±47 vs 407±46W). In both CYC and CON, high initial baseline values and small increases in plasma NO2- after NIT may have lowered the effect of the intervention implying that muscular and cardiovascular training status is likely not the only factors that influence the physiologic effects of NO3- supplementation.

The effect of nitrate supplementation on arterial blood gases, haemoglobin fractions and heart rate in Bos indicus cattle after exercise

The objective of this study was to investigate the effects of nitrate treatment on the arterial blood gas and haemoglobin fractions from Bos indicus steers after exercise. Bos indicus steers (n = 12; mean bodyweight ± s.e.m., 397 kg ± 10.84 kg) were used in this experiment to investigate the effects of three dose rates of nitrate salts (0, 30 or 50 g of nitrate/day) on arterial blood gases, methaemoglobin concentration, carboxyhaemoglobin concentration, oxyhaemoglobin concentration, total haemoglobin concentration, haematocrit, heart rate, and respiratory rate after exercise. Increasing the dose rate of nitrate resulted in a decrease in the partial pressure of oxygen (P = 0.004) in blood. Steers treated with 50 g nitrate/day had a decrease in oxyhaemoglobin concentration (P = 0.001) and a concomitant increase in methaemoglobin (P = 0.001) and carboxyhaemoglobin (P = 0.001) compared with steers treated with 0 or 30 g nitrate/day. Steers dosed with 50 g of nitrate had greater heart rates immediately after the exercise regimen compared with the steers dosed with 30 g of nitrate (P = 0.043) or no nitrate (P = 0.018). There was no difference between treatments for respiratory rate (P = 0.673) or rectal temperature (P = 0.207) after the exercise regimen. Feeding nitrate to Bos indicus cattle results in a decrease in the oxygen carrying capacity of their blood. It is likely that doses of nitrate greater than 50 g per day for this class of animal could induce hypoxaemic trauma if cattle have exercise imposed after consuming a nitrate supplement.

Effect of Dietary Nitrate Supplementation on Swimming Performance in Trained Swimmers.

Nitrate supplementation appears to be most ergogenic when oxygen availability is restricted and subsequently may be particularly beneficial for swimming performance due to the breath-hold element of this sport. This represents the first investigation of nitrate supplementation and swimming time-trial (TT) performance. In a randomized double-blind repeated-measures crossover study, ten (5 male, 5 female) trained swimmers ingested 140ml nitrate-rich (~12.5mmol nitrate) or nitrate-depleted (~0.01mmol nitrate) beetroot juice. Three hours later, subjects completed a maximal effort swim TT comprising 168m (8 × 21m lengths) backstroke. Preexercise fractional exhaled nitric oxide concentration was significantly elevated with nitrate compared with placebo, Mean (SD): 17 (9) vs. 7 (3)p.p.b., p = .008. Nitrate supplementation had a likely trivial effect on overall swim TT performance (mean difference 1.22s; 90% CI -0.18-2.6s; 0.93%; p = .144; d = 0.13; unlikely beneficial (22.6%), likely trivial (77.2%), most unlikely negative (0.2%)). The effects of nitrate supplementation during the first half of the TT were trivial (mean difference 0.29s; 90% CI -0.94-1.5s; 0.46%; p = .678; d = 0.05), but there was a possible beneficial effect of nitrate supplementation during the second half of the TT (mean difference 0.93s; 90% CI 0.13-1.70s; 1.36%; p = .062; d = 0.24; possibly beneficial (63.5%), possibly trivial (36.3%), most unlikely negative (0.2%)). The duration and speed of underwater swimming within the performance did not differ between nitrate and placebo (both p > .30). Nitrate supplementation increased nitric oxide bioavailability but did not benefit short-distance swimming performance or the underwater phases of the TT. Further investigation into the effects of nitrate supplementation during the second half of performance tests may be warranted.

Effects of Nitrate Supplementation on Nutrition, Performance and Methane Mitigation in Ruminants: A Review

Nitrate supplementation is a viable option to mitigate enteric methane emission and also to improve animal performance. It is a well established fact that bacteria from the rumen are able to use nitrate as electron acceptors, instead of carbon dioxide and when nitrate is used as an alternative electron acceptor, methane production is reduced. The reduction of nitrate to ammonia, consumes eight electrons and each mole of nitrate reduced could thus lower methane production by 1 mole. In addition, to inhibiting methane production, the end product of nitrate production ammonia, is an essential nutrient for the rumen microbial population for protein synthesis and for the growth of microbial cells. Microbial protein in turn is the source of amino acids, absorbed and used for animal growth, reproduction and milk production. Urea, which is quickly converted to ammonia in the rumen, is often included in ruminant diets as a nitrogen supplement. The replacement of urea with nitrates in ruminant diets is feasible, subject to the management of nitrate supplementation. A further useful feature of nitrate supplementation is that, small amounts of nitrogen oxides produced during the nitrate metabolism in the rumen inhibit the activities of some methanogens, potentially increasing the level of inhibition of methane production where nitrate is only a proportion of the total fermentable nitrogen in a diet.

Effect of nitrate supplementation on hepatic blood flow and glucose homeostasis: a double-blind, placebo-controlled, randomized control trial.

Nitric oxide alters gastric blood flow, improves vascular function, and mediates glucose uptake within the intestines and skeletal muscle. Dietary nitrate, acting as a source of nitric oxide, appears to be a potential low-cost therapy that may help maintain glucose homeostasis. In a randomized, double-blind, placebo-controlled crossover study, 31 young and older adult participants had a standardized breakfast, supplemented with either nitrate-rich beetroot juice (11.91 mmol nitrate) or nitrate-depleted beetroot juice as placebo (0.01 mmol nitrate). MRI was used to assess apparent diffusion coefficient (ADC), portal vein flux, and velocity. Plasma glucose, incretin, and C-peptide concentrations and blood pressure were assessed. Outcome variables were measured at baseline and hourly for 3 h. Compared with a placebo, beetroot juice resulted in a significant elevation in plasma nitrate and plasma nitrite concentration. No differences were seen for the young or older adult cohorts between placebo and beetroot juice for ADC, or portal vein flux. There was an interaction effect in the young adults between visits for portal vein velocity. Nitrate supplementation did not reduce plasma glucose, active GLP-1, total GLP-1, or plasma C-peptide concentrations for the young or older adult cohorts. Despite a significant elevation in plasma nitrite concentration following an acute dose of (11.91 mmol) nitrate, there was no effect on hepatic blood flow, plasma glucose, C-peptide, or incretin concentration in healthy adults.

The effect of nitrate supplementation on muscle contraction in healthy adults

This study examined the effect of dietary supplementation with inorganic nitrate ( ) on markers of contractile function in human knee extensors. In a double-blinded, randomized cross-over design, 18 (12 M) healthy participants undertook four days of supplementation with either nitrate-rich beetroot juice (NITRATE; days 1–3: 525 mg , day 4: 1050 mg ) or nitrate-depleted beetroot juice (PLACEBO). On the fourth day, isometric knee extension force was assessed during a series of voluntary and electrically evoked (stimulation) tests. In addition, muscular fatigue was examined in two separate continuous-stimulation (0.8 s tetanus with a 1:1 work:rest ratio for 102.4 s) fatigue tests, one with and one without blood flow restriction. There were no differences for maximum voluntary contraction, peak twitch force, half-relaxation time and the force–frequency relationship for stimulations up to 100 Hz between the NITRATE and PLACEBO trials. No differences between trials were observed in the non-restricted fatigue test, however NITRATE was found to attenuate the decline in force during the restricted test, such that the force at the 80 s mark (PLACEBO: 66 ± 11 vs. NITRATE 74 ± 9% of initial force; P = .01) and 102 s mark (PLACEBO: 47 ± 8% vs. NITRATE 55 ± 8%; P < .01) were significantly higher. These results suggest that four days of supplementation elicits peripheral responses in muscle that attenuate muscular fatigue during exhaustive exercise under hypovolemic conditions. This ergogenic action is likely attributable to improved Ca2+ handling in the muscle, or enhanced perfusion during ischemia.

Effect of Nitrate Supplementation on Cognitive Function and Neurovascular Coupling in Hypoxia

Cognitive dysfunction at high altitude (HA) may result from suboptimal matching of oxygen supply to neural demand (i.e. neurovascular coupling [NVC]). NVC is modulated by nitric oxide (NO) which initially decreases at HA. PURPOSE: Investigate the effect of NO-donor (nitrate) supplementation on NVC and cognitive function at HA. METHODS: 20 healthy men (23±3 yrs, BMI 24.3±3.0 kg·m-2) participated in this randomized, double-blind, crossover design study on two separate days. Following sea level (SL) cognitive/NVC testing, participants consumed either nitrate (NIT) or a NIT-depleted placebo (PLA). Participants then underwent 120 minutes of HA (11.5±0.2% O2) and all cognitive/NVC testing was repeated. NVC was assessed by measuring the change in mean middle cerebral artery (MCA) blood flow velocity during a cognitive challenge (incongruent Stroop task) using transcranial Doppler. Additional cognitive testing targeted the memory and executive function domains using memory recognition, maze, and choice reaction tasks. Brachial artery flow-mediated dilation (FMD) and salivary nitrite were assessed as systemic proxies of NO-metabolism. RESULTS: Salivary nitrite significantly increased following supplementation at HA for NIT compared to PLA (p<0.05). FMD and memory performance significantly decreased and executive function, reaction time and MCA reactivity were unchanged at HA in both conditions (p>0.05). CONCLUSION: NIT significantly increased salivary nitrite levels at HA compared to PLA. However, NIT was unable to prevent reductions in FMD or decreased memory at HA nor was NIT able to augment NVC at HA compared to SL. This research was supported by a Foundation Research Grant from the American College of Sports MedicineTable 1: NO-metabolism, cognitive function, and NVC at SL and HA between conditions (mean ± SD)

Effects of Nitrate Supplementation on Cardiovascular and Autonomic Reactivity in African-American Females.

Previous studies have shown that beetroot juice (BJ) decreases systolic blood pressure (SBP) and oxygen demand. This study tests the hypothesis that a beetroot juice (BJ) treatment increases heart rate variability (HRV) measured by the average standard deviation of normal-normal electrocardiogram RR intervals (SDNN) and the low frequency (LF), mainly sympathetic, fast Fourier transform spectral index of HRV. The subjects were 13 healthy young adult African-American females. Placebo control orange juice (OJ) and BJ treatments were given on separate days. Blood nitric oxide [NO], SBP and RR intervals were measured at rest and at constant workloads set to 40% and 80% of the predetermined VO2peak. Two hours after ingestion the BJ treatment increased [NO] and decreased SBP. BJ also increased SDNN at rest and at the 40% VO2peak workload, without significant effects on LF. SDNN was significantly greater after the BJ than after the OJ treatment, across the two physical activity conditions and SDNN was (negatively) correlated with SBP. These results suggest that BJ decreases SBP and increases HRV at rest and during aerobic exercise. Similar results in subjects with prehypertension or hypertension could translate to a dietary nitrate treatment for hypertension.

Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamics

NO3− supplementation via beetroot juice (BR) augments exercising skeletal muscle blood flow subsequent to its reduction to NO2− then NO. We tested the hypothesis that enhanced vascular control following BR would elevate the skeletal muscle O2 delivery/O2 utilization ratio (microvascular PO2, PmvO2) and raise the PmvO2 during the rest-contractions transition. Rats were administered BR (~0.8mmol/kg/day, n=10) or water (control, n=10) for 5 days. PmvO2 was measured during 180s of electrically induced (1Hz) twitch spinotrapezius muscle contractions. There were no changes in resting or contracting steady-state PmvO2. However, BR slowed the PmvO2 fall following contractions onset such that time to reach 63% of the initial PmvO2 fall increased (MRT1; control: 16.8±1.9, BR: 24.4±2.7s, p<0.05) and there was a slower relative rate of PmvO2 fall (Δ1PmvO2/τ1; control: 1.9±0.3, BR: 1.2±0.2mmHg/s, p<0.05). Despite no significant changes in contracting steady state PmvO2, BR supplementation elevated the O2 driving pressure during the crucial rest-contractions transients thereby providing a potential mechanism by which BR supplementation may improve metabolic control.

Dietary nitrate dramatically increases force in mouse skeletal muscle

Nitrate supplementation has beneficial effects on exercise performance, with both improved mitochondrial efficiency and reduced ATP cost of muscle force production implicated. It was the purpose of this study to examine if nitrate supplementation could improve Ca2+ handling and contractile function using skeletal muscles from C57bl/6 male mice given 0.1 mmol • kg−1 sodium nitrate in drinking water for 7 days (Nitrate). Age matched controls were provided water without added nitrate (Control). Myoplasmic free [Ca2+] ([Ca2+]i) was significantly elevated from 20–150 Hz stimulation in fast‐twitch muscle fibers dissected from Nitrate (n = 5) compared to Control mice (n = 7). This resulted in increased contractile force at stimulation frequencies up to 50 Hz. At 100 Hz stimulation, the rate of force development was ~35% faster in the Nitrate group. These changes were accompanied by increased expression of the Ca2+ handling proteins calsequestrin and the dihydropyridine receptor in fast‐twitch muscles of Nitrate mice. In conclusion, these results show a striking and novel effect of nitrate supplementation on intracellular Ca2+ handling and force production. These data provide a new mechanism by which nitrate can exert effects on muscle performance, and provide a potential new therapeutic role for nitrate in conditions with muscle weakness.