Effects Of Dietary Nitrate Research Articles

The effects of dietary nitrate on plasma glucose and insulin sensitivity in sheep.

Nitrate (NO3 ¯ ) is an effective non-protein nitrogen source for gut microbes and reduces enteric methane (CH4 ) production in ruminants. Nitrate is reduced to ammonia by rumen bacteria with nitrite (NO2 ¯ ) produced as an intermediate. The absorption of NO2 ¯ can cause methaemoglobinaemia in ruminants. Metabolism of NO3 ¯ and NO2 ¯ in blood and animal tissues forms nitric oxide (NO) which has profound physiological effects in ruminants and has been shown to increase glucose uptake and insulin secretion in rodents and humans. We hypothesized that absorption of small quantities of NO2 ¯ resulting from a low-risk dose of dietary NO3 ¯ will increase insulin sensitivity (SI ) and glucose uptake in sheep. We evaluated the effect of feeding sheep with a diet supplemented with 18g NO3 ¯ /kg DM or urea (Ur) isonitrogenously to NO3 ¯ , on insulin and glucose dynamics. A glucose tolerance test using an intravenous bolus of 1ml/kg LW of 24% (w/v) glucose was conducted in twenty sheep, with 10 sheep receiving 1.8% supplementary NO3 ¯ and 10 receiving supplementary urea isonitrogenously to NO3 ¯ . The MINMOD model used plasma glucose and insulin concentrations to estimate basal plasma insulin (Ib ) and basal glucose concentration (Gb ), insulin sensitivity (SI ), glucose effectiveness (SG ), acute insulin response (AIRg) and disposition index (DI). Nitrate supplementation had no effect on Ib (p>.05). The decrease in blood glucose occurred at the same rate in both dietary treatments (SG ; p=.60), and there was no effect of NO3 ¯ on either Gb , SI , AIRg or DI. This experiment found that the insulin dynamics assessed using the MINMOD model were not affected by NO3 ¯ administered to fasted sheep at a low dose of 1.8% NO3 ¯ in the diet.

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

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

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.

Dietary nitrate protects skin flap against ischemia injury in rats via enhancing blood perfusion

Insufficient blood supply is associated with high levels of necrosis in reconstructive surgery. Restoring blood flow to undersupplied ischemic tissue is the most important impact factor determining skin flap viability. Dietary nitrate, a significant source of nitric oxide, has multiple physiological functions, including regulator of blood flow, angiogenesis, and vasodilatation. However, the effects of dietary nitrate on ischemic skin flap remain unknown. The present study evaluated whether dietary nitrate supplementation altered blood flow of ischemic skin flap in rats. Our results showed that nitrate treatment significantly enhanced ischemic tissue survival. Mechanistically, nitrate therapy significantly increased serum nitrate and nitrite levels, blood perfusion, and angiogenesis. In addition, the circulating levels of Inflammatory mediators were decreased by nitrate supplementation. In conclusion, we demonstrated that dietary nitrate supplementation protected ischemic skin flap by enhancing ischemia-induced revascularization.

Effect of acute dietary nitrate supplementation on sympathetic vasoconstriction at rest and during exercise.

Dietary nitrate ( ) supplementation has been shown to reduce resting blood pressure. However, the mechanism responsible for the reduction in blood pressure has not been identified. Dietary supplementation may increase nitric oxide (NO) bioavailability, and NO has been shown to inhibit sympathetic vasoconstriction in resting and contracting skeletal muscle. Therefore, the purpose of this study was to investigate the hypothesis that acute dietary supplementation would attenuate sympathetic vasoconstrictor responsiveness at rest and during exercise. In a double-blind randomized crossover design, 12 men (23 ± 5 yr) performed a cold-pressor test (CPT) at rest and during moderate- and heavy-intensity alternate-leg knee-extension exercise after consumption of rich beetroot juice (~12.9 mmol ) or a -depleted placebo (~0.13 mmol ). Venous blood was sampled before and 2.5 h after the consumption of beetroot juice for the measurement of total plasma nitrite/ [NOx]. Beat-by-beat blood pressure was measured by Finometer. Leg blood flow was measured at the femoral artery via Doppler ultrasound, and leg vascular conductance (LVC) was calculated. Sympathetic vasoconstrictor responsiveness was calculated as the percentage decrease in LVC in response to the CPT. Total plasma [NOx] was greater (P < 0.001) in the (285 ± 120 µM) compared with the placebo (65 ± 30 µM) condition. However, mean arterial blood pressure and plasma catecholamines were not different (P > 0.05) between and placebo conditions at rest or during moderate- and heavy-intensity exercise. Sympathetic vasoconstrictor responsiveness (Δ% LVC) was not different (P > 0.05) between and placebo conditions at rest ( : -33 ± 10%; placebo: -35 ± 11%) or during moderate ( : -18 ± 8%; placebo: -20 ± 10%)- and heavy ( : -12 ± 8%; placebo: -11 ± 9%)-intensity exercise. These data demonstrate that acute dietary supplementation does not alter sympathetic vasoconstrictor responsiveness at rest or during exercise in young healthy males. NEW & NOTEWORTHY Dietary nitrate may increase nitric oxide bioavailability, and nitric oxide has been shown to attenuate sympathetic vasoconstriction in resting and contracting skeletal muscle and enhance functional sympatholysis. However, the effect of dietary nitrate on sympathetic vasoconstrictor responsiveness is unknown. Acute dietary nitrate supplementation did not alter blood pressure or sympathetic vasoconstrictor responsiveness at rest or during exercise in young healthy males.

Abstract P298: Normotensive Habitual Caffeine Consumers Experience No Change in Blood Pressure or Pulse Wave Velocity Following the Combined Consumption of Caffeine and Dietary Nitrate

Intro: Caffeine intake may elevate blood pressure (BP), while habitual consumption leads to developed tolerance, providing conflicting evidence for incurred changes in BP. Dietary nitrate consumption decreases BP and reduces arterial stiffness in patients with atherosclerosis and hypertension due to increased plasma nitrite and enhanced bioavailability of nitric oxide. However, a decline in BP for a healthy cohort could be an unwanted side effect for normotensive individuals. Less is known about the combined effects of dietary nitrate and caffeine on resting hemodynamics in a healthy population. Hypothesis: We hypothesized that caffeine supplementation would increase systolic blood pressure (SBP) and pulse wave velocity (PWV) while combined dietary nitrate consumption would attenuate this rise. Methods: In a randomized, double-blind, counterbalanced study, eight healthy, young adults who typically consumed some but not more than 500 mg caffeine/day completed 4 separate visits to the laboratory, each visit separated by one week. Prior to each visit, participants consumed a 4-day supplementation regimen of either dietary nitrate (12.4 mmol, NIT) or a placebo nitrate (PLN) combined with either caffeine (3 mg/kg, CAF) or placebo caffeine (PLC); this comprised 1 of 4 treatments. The final dose of NIT or PLN was consumed 2.5 hours prior to assessments while CAF or PLC was consumed 1 hour prior. Participants minimized consumption of dietary nitrate rich foods and caffeine during the 4 days leading up to their scheduled visit. Each visit consisted of measurements of peripheral SBP and diastolic blood pressure (DBP) with aortic central systolic and diastolic blood pressure (cSBP and cDBP, respectively) assessed noninvasively using pulse wave analysis. Measurement of arterial stiffness via applanation tonometry determined PWV. A linear mixed effects model analysis was performed to determine if supplementation regimen influenced hemodynamic parameters. Results: SBP of NIT+CAF (115±6 mmHg), PLN+CAF (117±9 mmHg), NIT+PLC (115±6 mmHg) and PLN+PLC (115±6 mmHg)(p=0.591) and PWV of NIT+CAF (5.5±1.1 m/s), PLN+CAF (5.8±0.7 m/s), NIT+PLC (5.8±0.6 m/s) and PLN+PLC (5.6±1.0 m/s) (p=0.353) were not statistically different between treatments. In addition, DBP (p=0.496), cSBP (p=0.656), cDBP (p=0.548), aortic augmentation index (p=0.054), and resting heart rate (p=0.646) were not different between treatments. Conclusion: Following 4 days of caffeine supplementation, habitual caffeine users did not experience any changes in resting hemodynamics when compared to a placebo supplement. In addition, dietary nitrate did not incur any changes in resting metrics whether or not it was consumed alongside caffeine. In this regard, habitual caffeine users are not affected by 3mg/kg doses of caffeine, and dietary nitrate (12.4 mmol/day) does not further reduce the BP of healthy normotensive adults.

Effect of dietary nitrate on enteric methane emissions, production performance and rumen fermentation of dairy cows grazing kikuyu-dominant pasture during summer

Dietary nitrate supplementation is an effective methane (CH4) mitigation strategy in total mixed ration based diets fed to ruminants. To date, limited information is available on the effect of dietary nitrate on CH4 production from grazing dairy cows. Fifty-four multiparous Jersey cows were subjected to a randomised complete block design (blocked according to milk yield, days in milk and parity) to evaluate the effect of three dietary nitrate levels on enteric CH4 emissions and cow production performance. Additionally, six rumen-cannulated cows in a replicated 3 × 3 Latin square design were used in a rumen study. Dietary treatments consisted of concentrate fed at 5.4 kg of DM/cow per day containing one of three levels of dietary nitrate: 0 g (control), 11 g (low nitrate), and 23 g of nitrate/kg of dry matter (DM; high nitrate). Cows grazed late-summer pasture containing approximately 3 g of nitrate/kg of DM. Concentrates were formulated to be isonitrogenous, by substituting urea, and isoenergetic. Cows were gradually adapted to concentrates over a 3-wk period before the onset of a 57-d experimental period. Enteric CH4 emissions and total dry matter intake (DMI) from 11 cows per treatment were measured during one 6-d measurement period using the sulphur hexafluoride tracer gas technique. Individual pasture DMI was determined using TiO2 and indigestible neutral detergent fibre (NDF). Milk yield decreased by approximately 12% when feeding the high nitrate diet compared with the control and low nitrate diets. Although total DMI was unaffected by treatment, concentrate DMI decreased linearly (5.5–3.7 kg/d) while pasture DMI increased linearly (9.1–11.4 kg/d) with increasing dietary nitrate addition. Methane production (313–280 g/d), CH4 yield (21.8–18.7 g/kg of DMI) and CH4 energy per gross energy intake (6.9–5.9%) tended to decrease linearly with increasing dietary nitrate addition. Diurnal ruminal pH of the high nitrate group was greater, for selective periods after concentrate feeding, than the control and low nitrate groups. Spot sample ruminal pH (6.2–6.3) tended to increase while total volatile fatty acid (VFA) concentration (99.9–104 mM/L) increased quadratically with increasing dietary nitrate addition. Individual VFA concentrations were unaffected by treatment. Rate of NDF disappearance (2.4–2.8%/h) after 18 h of ruminal incubation tended to increase quadratically with increasing dietary nitrate addition. Dietary nitrate fed to grazing dairy cows tended to decrease CH4 emissions while improving the fibrolytic environment of the rumen. However, when feeding high levels of dietary nitrate a decrease in milk yield could be expected due to a decrease in concentrate DMI.

The effect of beetroot juice supplementation on repeat-sprint performance in hypoxia

ABSTRACTThis investigation assessed the effect of dietary nitrate (NO3−) supplementation, in the form of beetroot juice (BR), on repeat-sprint performance in normoxia and normobaric hypoxia. 12 male team-sport athletes (age 22.3 ± 2.6 y, VO2peak 53.1 ± 8.7 mL.kg−1.min−1) completed three exercise trials involving a 10 min submaximal warm-up and 4 sets of cycling repeat-sprint efforts (RSE; 9 × 4 s) at sea level (CON), or at 3000 m simulated altitude following acute supplementation (140 mL) with BR (HYPBR; 13 mmol NO3−) or NO3–depleted BR placebo (HYPPLA). Peak (PPO) and mean (MPO) power output, plus work decrement were recorded during the RSE task, while oxygen consumption (VO2) was measured during the warm-up. There were no significant differences observed between HYPBR and HYPPLA for PPO or MPO; however, work decrement was reduced in the first RSE set in HYPBR compared with HYPPLA. There was a moderate effect for VO2 to be lower following BR at the end of the 10 min warm-up (ES = 0.50 ± 0.51). Dietary NO3− may not improve repeat-sprint performance in hypoxia but may reduce VO2 during submaximal exercise. Therefore, BR supplementation may be more effective for performance improvement during predominantly aerobic exercise.

Isolation, characterization and strain selection of a Paenibacillus species for use as a probiotic to aid in ruminal methane mitigation, nitrate/nitrite detoxification and food safety

The effects of dietary nitrate and Paenibacillus 79R4 (79R4), a denitrifying bacterium, when co-administered as a probiotic, on methane emissions, nitrate and nitrite-metabolizing capacity and fermentation characteristics were studied in vitro. Mixed populations of rumen microbes inoculated with 79R4 metabolized all levels of nitrite studied after 24 h in vitro incubation. Results from in vitro simulations resulted in up to 2 log10 colony forming unit reductions in E. coli O157:H7 and Campylobacter jejuni when these were co-cultured with 79R4. Nitrogen gas was the predominant final product of nitrite reduction by 79R4. When tested with nitrate-treated incubations of rumen microbes, 79R4 inoculation (provided to achieve 106 cells/mL rumen fluid volume) complemented the ruminal methane-decreasing potential of nitrate (P < 0.05) while concurrently increasing fermentation efficiency and enhancing ruminal nitrate and nitrite-metabolizing activity (P < 0.05) compared to untreated and nitrate only-treated incubations.

The Effect of Dietary Nitrate on Vascular Function in Chronic Kidney Disease

PURPOSEThe purpose of this study was to test the hypothesis that an acute dose of 12.6 mmol dietary nitrate in the form of concentrated beetroot juice (BRJ) would improve measures of microvascular and conduit artery endothelial function in patients with moderate to severe chronic kidney disease (CKD).METHODSFifteen adults with moderate to severe CKD participated in this double blind, randomized, crossover study (61±4 yrs; 11 males; eGFR 49.2±3.4 ml•min−1•1.73 m2). Participants reported to the laboratory and baseline blood pressure (BP) was measured and a baseline blood sample obtained for determination of NO metabolites (NOm; Nitrate, nitrite, s‐nitrosothiols and metal bound NO). Participants were then randomized to ingest 12.6 mmol of BRJ or a nitrate depleted placebo (PLA). Vascular testing began 2.5 hours post beverage ingestion. A second blood sample was obtained and post‐ingestion BP was recorded. Microvascular function was assessed via the cutaneous response to local heating measured by laser Doppler flowmetry coupled with microdialysis, and conduit artery function was assessed via brachial artery flow‐mediated dilation (FMD). Arterial stiffness (via carotid‐femoral pulse wave velocity, PWV) was also measured. The entire protocol was repeated a minimum of 7 days later in the other condition.RESULTSPlasma NOm was not different between conditions at baseline but was significantly increased 2.5 hours post BRJ ingestion compared to pre‐ingestion values, as well as compared to post PLA values (PREPLA 53.0±11.6 POSTPLA 33.2±9.9 mM; PREBRJ 57.3±21.4 vs POSTBRJ1068.0±106.6 mM). Mean arterial pressure (MAP) was not different between conditions at baseline or 2.5 hours post, however the change in MAP from pre‐ingestion baseline to 2.5 hours post ingestion was significantly different between conditions (ΔMAPPLA 2.0±2.1 vs ΔMAPBRJ −3.2±2.6 mmHg, p&gt;0.05). The plateau phase of the cutaneous response to local heating was significantly greater in the BRJ condition compared to PLA (PLA 83.4±2.2 vs BRJ 88.8±1.7%CVCmax; p&lt;0.05). The NOS mediated contribution to the plateau phase as assessed via L‐NAME infusion was not different between conditions. We did not observe any improvements in FMD or PWV.CONCLUSIONAn acute dose of 12.6 mmol dietary nitrate significantly improves microvascular function in patients with moderate to severe CKD.Support or Funding InformationThis research was supported by an ACSM Foundation Research Grant from the American College of Sports Medicine Foundation and NIH grant HL113514.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of Dietary Nitrate on Blood Pressure and Vascular Control in Post‐Menopausal Hypertensive Women

Individuals with hypertension exhibit abnormal pressor responses during rest‐to‐exercise transitions, significantly increasing the likelihood of sudden cardiac events. Dietary nitrate supplementation can lower resting blood pressure in patients with hypertension and improve bulk muscle blood flow in older healthy adults. However, investigations using dietary nitrate as a non‐pharmacological intervention in post‐menopausal women diagnosed with hypertension are lacking. Therefore, the purpose of the current investigation was to determine if acute dietary nitrate supplementation would improve the pressor response to exercise and increase forearm blood flow during steady‐state hand‐grip exercise in post‐menopausal hypertensive women. It was hypothesized that the pressor response to exercise would be attenuated and muscle blood flow would be improved in the nitrate‐rich (NR) versus nitrate‐poor (NP) treatment.METHODSTen hypertensive post‐menopausal women [age 56 ± 3 years (mean±SD); height 165 ± 2 cm; mass 84 ± 13 kg; body mass index 31 ± 5 kg/m2] agreed to participate in the current study. Patients underwent a randomized double‐blind placebo‐controlled trial with a NR or NP beet root juice supplement. Blood samples were taken at the beginning of each testing session (~2 h post ingestion) to determine plasma nitrite levels. Forearm blood flow (FBF) was measured via ultrasonography at the brachial artery of the exercising limb. Beat‐by‐beat blood pressure and heart rate were recorded throughout the trial on the non‐exercising limb. After resting measurements were completed, patients performed hand‐grip exercise at 20% maximal voluntary contraction (MVC) for five minutes to obtain steady‐state blood flow and blood pressure response to exercise.RESULTSPlasma nitrite levels were significantly higher during the NR (809 ± 146 nM) than the NP (79 ± 19 nM) condition. No differences were found between conditions for resting blood flow (NR: 64±2; NP: 62 ± 4 ml min−1; P &gt; 0.05), systolic (NR: 144 ± 2; NP: 145 ± 2 mmHg−1; P &gt; 0.05) or diastolic blood pressure (NR: 78 ± 1; NP: 80 ± 1 mmHg−1; P &gt; 0.05). In addition, there were no significant differences across 10‐second bins (e.g., 0–10, 11–20 seconds) during the first minute pressor response to hand‐grip exercise in either condition (systolic: P &gt; 0.05; diastolic: P &gt; 0.05). As such, the rate pressure product was not significantly different during steady‐state between conditions (NR: 11,562 ± 437; NP: 11,728 ± 437 bpm · mmHg−1; P &gt; 0.05). During steady‐state exercise, FBF (NR: 189 ± 8; NP: 218 ± 8 ml min−1; P = 0.03) and forearm vascular conductance (FVC) (NR: 157 ± 4; NP: 183 ± 4 ml min−1; P = 0.04) were significantly lower during the steady‐state NR condition.CONCLUSIONAcute dietary nitrate supplementation did not improve the pressor response to hand‐grip exercise in hypertensive post‐menopausal women. However, it is important to note that steady‐state FBF (~30 ml min−1) and FVC (~27 ml min mmHg−1) were significantly reduced during the nitrate‐rich condition, which suggests a reduced O2 cost for a given workload because blood flow typically matches metabolic rate.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract P242: Dietary Nitrate Does not Reduce Resting Metabolic Rate or Oxidative Stress in Healthy Males

Introduction: Nitric oxide (NO) is a vasodilator that increases blood flow by promoting relaxation of endothelium. Dietary nitrate supplementation increases plasma nitrite, a marker of overall NO bioavailability. Previously, acute dietary nitrate supplementation has been shown to reduce oxygen consumption and improve tolerance during submaximal exercise in healthy populations. Less is known about the effect of dietary nitrate on oxygen consumption at rest. Hypothesis: We hypothesized that dietary nitrate supplementation would reduce resting metabolic rate (RMR) and oxidative stress (8-isoprostane) at rest, via enhanced NO bioavailability via the oxygen independent Nitrate-Nitrite-Nitric Oxide pathway in healthy, young males. Methods: In a randomized, double-blind, cross-over study, ten healthy, young males (21 ± 2 years) visited the laboratory on 5 separate occasions. Participants completed informed consent paperwork and underwent protocol familiarization during visit 1. Prior to visits 2 and 4, participants fasted for 12 hours and adhered to an NIH-approved low-nitrate diet for 48 hours. During visits 2 and 4, an initial blood draw was performed to analyze baseline plasma nitrite and 8-isoprostane. Participants then completed a 30-minute resting metabolic rate (RMR) test. Two hours prior to visits 3 and 5, participants consumed either a placebo or dietary nitrate supplement (negligible and 6.2 mmol nitrate, respectively). During visits 3 and 5, participants also had blood drawn for analysis of the previously stated measurements, and completed an RMR test. Visits 2 and 3 were on consecutive days, followed by a week-long washout period between visit 3 and visit 4, while visit 4 and 5 also occurred on consecutive days. Results: Plasma nitrite significantly increased following dietary nitrate consumption compared to baseline values (27.56 ± 7.58 and 1.25 ± 1.51 arbitrary units, respectively). No difference was present between nitrate and baseline measurements for 8-isoprostane (155.75 ± 57.01 and 198.42 ± 66.44 pg/mL, respectively; p=0.55) and RMR (2086.60 ± 202.23 and 2050.00 ± 209.23 kcal/day, respectively; p=0.13). Conclusion: Dietary nitrate supplementation increases plasma nitrite, but does not change resting metabolic rate following an acute dose of dietary nitrate in healthy males. Individuals consuming dietary nitrate as an ergogenic aid during exercise may not, however, experience similar changes in their resting metabolism. The lack of change in oxidative stress may have been associated with the overall health of the cohort examined. Future research should investigate the clinical implications of dietary nitrate in populations with decreased NO bioavailability and associated endothelial disfunction (and elevated oxidative stress). In such populations, dietary nitrate may provide benefit. However, in a healthy cohort, dietary nitrate exerts minimal effects.

The Effect of Dietary Nitrate on Nocturnal Sleep-Disordered Breathing and Arterial Oxygen Desaturation at High Altitude.

Patrician, Alexander, Harald Engan, David Lundsten, Ludger Grote, Helena Vigetun-Haughey, and Erika Schagatay. The effect of dietary nitrate on nocturnal sleep-disordered breathing and arterial oxygen desaturation at high altitude. High Alt Med Biol 19:21-27, 2018.-Sleep-disordered breathing and fluctuations in arterial oxygen saturation (SaO2) are common during sleep among lowlanders ascending to high altitude. Dietary nitrate (NO3-) supplementation has been shown to lower the O2 consumption in various conditions. Our objective was to investigate whether dietary NO3- could reduce sleep-disordered breathing and SaO2 desaturation during sleep at altitude. Cardiorespiratory responses during sleep were measured in 10 healthy lowlanders at 330 m and then again in the Himalayas at 3700-4900 m. Each subject received two 70 mL shots of either beetroot juice (BR; ∼5.0 mmol NO3- per shot) or placebo (PL: ∼0.003 mmol NO3- per shot) in a single-blinded, weighted order over two consecutive nights at altitude. At 2.5-4.5 hours into sleep at altitude, BR increased the SaO2 desaturation drop (4.2 [0.1]% with PL vs. 5.3 [0.4]% with BR; p = 0.024) and decreased the SaO2 desaturation duration (14.1 [0.9] seconds with PL to 11.1 [0.9] seconds with BR; p = 0.0.041). There was a reduction in breaths with flow limitation (p = 0.025), but no changes in Apnea-Hypopnea Index (AHI), mean and minimum SaO2. The study suggests BR supplementation does not improve AHI or oxygenation, but may increase fluctuations in arterial O2 saturation during sleep at altitude in native lowlanders.

Effects of dietary nitrate on respiratory physiology at high altitude - Results from the Xtreme Alps study

Nitric oxide (NO) production plays a central role in conferring tolerance to hypoxia. Tibetan highlanders, successful high-altitude dwellers for millennia, have higher circulating nitrate and exhaled NO (ENO) levels than native lowlanders. Since nitrate itself can reduce the oxygen cost of exercise in normoxia it may confer additional benefits at high altitude. Xtreme Alps was a double-blinded randomised placebo-controlled trial to investigate how dietary nitrate supplementation affects physiological responses to hypoxia in 28 healthy adult volunteers resident at 4559 m for 1 week; 14 receiving a beetroot-based high-nitrate supplement and 14 receiving a low-nitrate ‘placebo’ of matching appearance/taste. ENO, vital signs and acute mountain sickness (AMS) severity were recorded at sea level (SL) and daily at altitude. Moreover, standard spirometric values were recorded, and saliva and exhaled breath condensate (EBC) collected. There was no significant difference in resting cardiorespiratory variables, peripheral oxygen saturation or AMS score with nitrate supplementation at SL or altitude. Median ENO levels increased from 1.5/3.0 mPa at SL, to 3.5/7.4 mPa after 5 days at altitude (D5) in the low and high-nitrate groups, respectively (p = 0.02). EBC nitrite also rose significantly with dietary nitrate (p = 0.004), 1.7–5.1 μM at SL and 1.6–6.3 μM at D5, and this rise appeared to be associated with increased levels of ENO. However, no significant changes occurred to levels of EBC nitrate or nitrosation products (RXNO). Median salivary nitrite/nitrate concentrations increased from 56.5/786 μM to 333/5,194 μM with nitrate supplementation at SL, and changed to 85.6/641 μM and 341/4,553 μM on D5. Salivary RXNO rose markedly with treatment at SL from 0.55 μM to 5.70 μM. At D5 placebo salivary RXNO had increased to 1.90 μM whilst treatment RXNO decreased to 3.26 μM. There was no association with changes in any observation variables or AMS score. In conclusion, dietary nitrate supplementation is well tolerated at altitude and significantly increases pulmonary NO availability and both salivary and EBC NO metabolite concentrations. Surprisingly, this is not associated with changes in hemodynamics, oxygen saturation or AMS development.

Abstract P275: A Randomized Clinical Trial on Dietary Nitrate and Blood Pressure

Background: Elevated blood pressure (BP) is a major risk factor for cardiovascular disease and premature death worldwide. Hypertension (i.e. BP of ≥140/90 mmHg) is even considered the leading risk factor for global burden of disease. Dietary strategies preventing hypertension includes the Dietary Approaches to Stop Hypertension eating plan. A vegetarian diet and high vegetable intake has also shown beneficial effects on BP regulation. In the last 10 years there is an emerging interest in the positive effects of dietary nitrate (NO3 - ). Inorganic nitrate is converted to nitric oxide (NO) in our body with vasodilatory effects. Vegetables alone contribute with 60-80% (60-80 of 100) of the total nitrate intake in humans and the highest concentrations of this anion are found in green leafy vegetables and beetroots. Several short term studies have shown that administration of nitrate salts or high nitrate vegetables (HNV) have BP lowering effects. A large scale randomized clinical trial is needed to explore long term effects on BP after daily intake of HNV. Methods: The Di etary Ni tric O xide (DINO) study is a single site, randomized clinical trial including subjects (n = 300) between 50-70y with SBP 130-159 mm Hg. A wash out period of 2 weeks is followed by randomization to one of three intervention groups: HNV containing 300 mg nitrate + placebo pill, low nitrate vegetables (LNV) + nitrate supplement (300mg potassium nitrate) or LNV + a placebo pill. All subjects will have a constant vegetable intake during 5 weeks of HNV or LNV provided weekly by the investigators, to consume together with their normal diet. After the wash out period and in the last week of the study 24h ambulatory BP, 24h urine collection, and blood- and saliva samples are taken. Lifestyle habits are also monitored during the study. The primary endpoint is systolic ambulatory BP with 85% (85 of 100) power to detect a difference of 2mm Hg between the groups. Conclusion: The DINO study is designed to investigate the potential contribution of inorganic nitrate to the BP lowering effect attributed to vegetables. In addition, the three armed design makes it possible to evaluate natural sources of nitrate compared to supplements.

Effects of dietary nitrate on metabolic status and myocardial ischaemia-reperfusion injury in type 2 diabetic rats

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

The Effect of Dietary Nitrate on the Physiological Responses to 3-Weeks Sprint Interval Training.

Dietary nitrate (NIT) supplementation has been shown to increase nitric oxide (NO) metabolites and enhance exercise performance. Sprint interval training (SIT) has been shown to improve aerobic fitness following 2-4 weeks of training. Considering NIT has been shown to enhance intermittent high intensity exercise the addition of NIT prior to SIT may enhance the physiological changes in aerobic fitness. PURPOSE: To investigate whether dietary nitrate ingested prior to SIT can enhance the physiological adaptations to SIT. METHODS: 27 participants completed an initial incremental ramp exercise test to exhaustion (IXT) for determination of VO2max, HRmax and WRmax. Participants were subsequently randomly assigned to a control group (CONT; n=8), SIT + placebo (PLA) group (n=10) or a SIT + NIT group (n=9) and were matched based on VO2max. Participants in each of the SIT groups then underwent 3-weeks of SIT consisting of 4-6 repeated 15 s all out sprints on a cycle ergometer, interspersed with 4 min active recovery. Participants consumed either a NIT or PLA dose 2.5 h prior to each training session. The dose consisted of 2 x 60 ml nitrate gels (∼8.1 mmol nitrate) or NIT-depleted PLA. In the control group participants were asked to maintain their normal lifestyle throughout the 3 week training period. Upon completion of the SIT protocol or CONT condition all participants repeated the initial IXT 48 h following the final training session. Differences between groups, time points and their interaction were established by mixed methods repeated measures ANOVA. RESULTS: There were no differences in VO2max prior to training (CONT: 44.8 ± 8.1, SIT + PLA: 40.6 ± 7.3, SIT + NIT: 42.3 ± 6.6 ml•kg•min-1, P=0.494) but VO2max improved pre - post training (P=0.019). Post-hoc analysis revealed changes in VO2max occurred in the SIT + NIT group (45.1 ± 9.3 ml•kg•min-1, 6.7 %, P=0.026) but not the SIT + PLA (42.5 ± 5 ml•kg•min-1, 4.7 %, P=0.097) or CONT groups (45.2 ± 7.8 ml•kg•min-1, 1 %, P=0.738). WRmax improved from pre - post training in both SIT groups (PLA: 274 ± 42 - 287 ± 42 W, P=0.006, NIT: 286 ± 47 - 314 ± 55 W, P<0.001) however no changes were seen in the CONT group (291 ± 60 - 287 ± 63 W, P=0.352). CONCLUSIONS: Results from the current study suggest that NIT may enhance the aerobic adaptations to SIT however the mechanism underpinning this response is currently unknown.

Effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance.

The aim of this study was to examine the acute supplementation effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance. Using a randomized, counterbalanced, double-blind Latin-square design, 14 competitive female cyclists (age: 31 ± 7 years; height: 1.69 ± 0.07 m; body mass: 61.6 ± 6.0 kg) completed four 20-km time trials on a racing bicycle fitted to a turbo trainer. Approximately 2.5 hours before each trial, subjects consumed a 70-ml dose of concentrated beetroot juice containing either 0.45 g of dietary nitrate or with the nitrate content removed (placebo). One hour before each trial, subjects consumed a capsule containing either 5 mg·kg of caffeine or maltodextrin (placebo). There was a significant effect of supplementation on power output (p = 0.001), with post hoc tests revealing higher power outputs in caffeine (205 ± 21 W) vs. nitrate (194 ± 22 W) and placebo (194 ± 25 W) trials only. Caffeine-induced improvements in power output corresponded with significantly higher measures of heart rate (caffeine: 166 ± 12 b·min vs. placebo: 159 ± 15 b·min; p = 0.02), blood lactate (caffeine: 6.54 ± 2.40 mmol·L vs. placebo: 4.50 ± 2.11 mmol·L; p < 0.001), and respiratory exchange ratio (caffeine: 0.95 ± 0.04 vs. placebo: 0.91 ± 0.05; p = 0.03). There were no effects (p ≥ 0.05) of supplementation on cycling cadence, rating of perceived exertion, (Equation is included in full-text article.), or integrated electromyographic activity. The results of this study support the well-established beneficial effects of caffeine supplementation on endurance performance. In contrast, acute supplementation with dietary nitrate seems to have no effect on endurance performance and adds nothing to the benefits afforded by caffeine supplementation.

Characterization of the rat oral microbiome and the effects of dietary nitrate.

The nitrate-nitrite-NO pathway to nitric oxide (NO) production is a symbiotic pathway in mammals that is dependent on nitrate reducing oral commensal bacteria. Studies suggest that by contributing NO to the mammalian host, the oral microbiome helps maintain cardiovascular health. To begin to understand how changes in oral microbiota affect physiological functions such as blood pressure, we have characterized the Wistar rat nitrate reducing oral microbiome. Using 16S rRNA gene sequencing and analysis we compare the native Wistar rat tongue microbiome to that of healthy humans and to that of rats with sodium nitrate and chlorhexidine mouthwash treatments. We demonstrate that the rat tongue microbiome is less diverse than the human tongue microbiome, but that the physiological activity is comparable, as sodium nitrate supplementation significantly lowered diastolic blood pressure in Wistar rats and also lowers blood pressure (diastolic and systolic) in humans. We also show for the first time that sodium nitrate supplementation alters the abundance of specific bacterial species on the tongue. Our results suggest that the changes in oral nitrate reducing bacteria may affect nitric oxide availability and physiological functions such as blood pressure. Understanding individual changes in human oral microbiome may offer novel dietary approaches to restore NO availability and blood pressure.

Use of nitrate and Propionibacterium acidipropionici to reduce methane emissions and increase wool growth of Merino sheep

The effects of dietary nitrate and of Propionibacterium acidipropionici (PA) on methane and nitrous oxide emissions, methaemoglobinaemia, volatile fatty acid (VFA) concentration and productivity of sheep were studied. It was hypothesised that PA supplementation would increase the rate of nitrite reduction to ammonia in the rumen and therefore reduce risks of methaemoglobinaemia. Fine-wool Merino wethers (n = 28; 31.8 ± 3.7 kg; 11 months of age) were acclimated to four isonitrogenous and isoenergetic diets based on oaten chaff (1.0 kg/day) supplemented with either urea (1.1% of DM; T1 and T2) or a nitrate source (2.0% of DM; T3 and T4) while T2 and T4 were also supplemented with PA (11.5 × 1010 CFU/day). Replacing urea with nitrate lowered methane production (g/day) by 19% and methane yield (g/kg DMI) by 15%, improved clean wool growth by 12% (P &lt; 0.001) and tended to increase skin temperature (P &lt; 0.1). Nitrate increased ruminal acetate to propionate ratio by 27%, increased plasma nitrite and nitrate concentrations and blood methaemoglobin (MetHb) level up to 45% of total haemoglobin. Nitrous oxide emission from sheep confined in respiration chambers was higher (P &lt; 0.001) when nitrate was fed, lowering the net benefit of methane mitigation on global warming potential (CO2 equivalents/kg DMI) by 18%. In contrast, PA had little effect, decreasing total VFA concentration (P &lt; 0.05), increasing rumen pH (P &lt; 0.05) and clean wool growth (P &lt; 0.05) of urea-fed sheep. This study confirmed the beneficial effects of nitrate on net greenhouse gas reduction and wool growth, but showed that methaemoglobinaemia risks may be higher when diets are fed at a restricted level and contain only low levels of readily fermented carbohydrate. PA supplementation was not effective in reducing methaemoglobinaemia, but did increase clean wool growth of urea-fed sheep.