Effects of chronic beetroot juice supplementation on maximum oxygen uptake, velocity associated with maximum oxygen uptake, and peak velocity in recreational runners: a double-blinded, randomized and crossover study.

PURPOSE: This study investigated the effects of chronic 3-day beetroot juice (BRJ) supplementation on maximum oxygen uptake (VO2max), velocity associated with VO2max(vVO2max), and peak velocity (Vpeak) in recreational runners. METHODS: Thirteen male recreational runners (age 28.2 ± 3.0 years, height 176.8 ± 0.1 cm, body mass 74.4 ± 9.5 kg) performed four tests on a treadmill in a randomized, double-blind, crossover design: two maximum incremental tests to determine VO2max and vVO2max, and two tests to determine Vpeak. Trials were performed following 3 days of supplementation of NO3--rich BRJ in natura (8.4 mmol NO3- day- 1) or BRJ NO3--depleted placebo (0.01 mmol NO3- day- 1), with the last dose being ingested 2 h before each test. During the tests, maximum heart rate (HRmax), maximal rating of perceived exertion (RPEmax), pre- and post-test glucose concentrations (Glucpre, Glucpost), and peak blood lactate concentration were determined. RESULTS: VO2max was higher following BRJ vs PLA (46.6 ± 6.4 vs 45.1 ± 5.8 mL kg- 1 min- 1; P = 0.022), as well as vVO2max (14.5 ± 0.8 vs 13.9 ± 1.0 km h- 1P = 0.024) and Vpeak (15.5 ± 1.1 vs 15.2 ± 1.2 km h- 1P = 0.038), with no differences in the other variables. CONCLUSION: Consumption of NO3--rich BRJ in natura (8.4 mmol NO3- day- 1) once per day for 3 days improved VO2max, vVO2max and Vpeak in recreational runners without changing the other analyzed variables.

Dietary interventions for fetal growth restriction - therapeutic potential of dietary nitrate supplementation in pregnancy.

Fetal growth restriction (FGR) affects around 5% of pregnancies and is associated with significant short- and long-term adverse outcomes. A number of factors can increase the risk of FGR, one of which is poor maternal diet. In terms of pathology, both clinically and in many experimental models of FGR, impaired uteroplacental vascular function is implicated, leading to a reduction in the delivery of oxygen and nutrients to the developing fetus. Whilst mechanisms underpinning impaired uteroplacental vascular function are not fully understood, interventions aimed at enhancing nitric oxide (NO) bioavailability remain a key area of interest in obstetric research. In addition to endogenous NO production from the amino acid l-arginine, via nitric oxide synthase (NOS) enzymes, research in recent years has established that significant NO can be derived from dietary nitrate, via the 'alternative NO pathway'. Dietary nitrate, abundant in green leafy vegetables and beetroot, can increase NO bioactivity, conferring beneficial effects on cardiovascular function and blood flow. Given the beneficial effects of dietary nitrate supplementation to date in non-pregnant humans and animals, current investigations aim to assess the therapeutic potential of this approach in pregnancy to enhance NO bioactivity, improve uteroplacental vascular function and increase fetal growth.

Effects of oral sodium nitrate on forearm blood flow, oxygenation and exercise performance during acute exposure to hypobaric hypoxia (4300 m).

A reduction in oxygen transport contributes to impaired exercise capacity at high altitude. Since blood flow is mediated, in part, by nitric oxide (NO), we hypothesized that sodium nitrate provided before forearm grip exercise performed at a simulated altitude of 4300 m (hypobaric hypoxia (HH)) would increase forearm blood flow and oxygenation, and decrease the decrement in grip performance. In a double-blind, randomized crossover study, 10 healthy subjects (9 males and 1 female) performed continuous (CGrip) and repeated rhythmic (RGrip) isometric forearm exercise until task failure in normobaric normoxia (NN), 2.5 h following consumption of placebo and sodium nitrate (15 mmol) in HH, and then again post-HH at sea-level pressure. Measurements included forearm blood flow (FBF) and anterior forearm tissue oxygenation (StO2), mean arterial blood pressure (MAP), arterial blood O2 saturation (SpO2), plasma NO reaction products (NOx) and nitrite, and exhaled NO (PENO). Compared to baseline testing in NN, performing CGrip and RGrip exercise in HH resulted in significant reductions in forearm blood flow, SaO2 and StO2, responses that were accompanied by significant performance decrements (∼10%) in both CGrip and RGrip exercise. In spite of a 10-fold increase in plasma NOx levels and a significant decrease in MAP during CGrip exercise following nitrate consumption, there were no significant main effects of treatment (placebo vs. sodium nitrate) for forearm blood flow, SpO2, StO2, or grip performance. PENO remained unchanged between NN, HH and post-HH conditions with placebo, but increased (∼24%) following nitrate supplementation in HH and post-HH. These data do not support a benefit in consuming a single dose of supplemental nitrate on forearm blood flow and isometric exercise in healthy adults at a simulated altitude of 4300 m.

Dose-dependent effects of dietary nitrate on the oxygen cost of moderate-intensity exercise: Acute vs. chronic supplementation.

PURPOSE: To investigate whether chronic supplementation with a low or moderate dose of dietary nitrate (NO3(-)) reduces submaximal exercise oxygen uptake (V˙O2) and to assess whether or not this is dependent on acute NO3(-) administration prior to exercise. METHODS: Following baseline tests, 34 healthy subjects were allocated to receive 3 mmol NO3(-), 6 mmol NO3(-) or placebo. Two hours following the first ingestion, and after 7, 28 and 30 days of supplementation, subjects completed two moderate-intensity step exercise tests. On days 28 and 30, subjects in the NO3(-) groups completed the test 2 h post consumption of a NO3(-) dose (CHR + ACU) and a placebo dose (CHR). RESULTS: Plasma nitrite concentration ([NO2(-)]) was elevated in a dose-dependent manner at 2 h, 7 days and 28-30 days on the CHR + ACU visit. Compared to pre-treatment baseline, 6 mmol NO3(-) reduced the steady-state V˙O2 during moderate-intensity exercise by 3% at 2 h (P = 0.06), 7 days and at 28-30 days (both P < 0.05) on the CHR + ACU visit, but was unaffected by 3 mmol NO3(-) at all measurement points. On the CHR visit in the 6 mmol group, plasma [NO2(-)] had returned to pre-treatment baseline, but the steady-state V˙O2 remained reduced. CONCLUSION: Up to ∼4 weeks supplementation with 6 but not 3 mmol NO3(-) can reduce submaximal exercise V˙O2. A comparable reduction in submaximal exercise V˙O2 following chronic supplementation with 6 mmol NO3(-) can be achieved both with and without the acute ingestion of NO3(-) and associated elevation of plasma [NO2(-)].

Sodium Nitrate Improves Oxidative Energy Contribution and Reduces Phosphocreatine Contribution During High-Intensity Intermittent Exercise.

The present study aimed to verify the effect of acute nitrate supplementation on oxidative, phosphocreatine, and glycolytic energy contribution (COXI, CPCr, and CLAC, respectively) during a high-intensity intermittent exercise (HIIE). Fifteen physically active subjects were submitted to incremental running test on a treadmill and two random HIIE (10 × 1 min at maximal aerobic speed with 1 min of passive recovery) in the following conditions: sodium nitrate (SN) or Placebo (PL). Repeated measure ANOVA was used to compare COXI, and CPCr within the 10 efforts. Student t test was used to compare total COXI, CPCr, CLAC, as well oxidative and non-oxidative contribution. Considering the 10 efforts, COXI presented the main effect for condition (F = 16.7; p = .001; SN: 1.9 ± 0.1 L; PL: 1.6 ± 0.1 L), and no interaction effect (F = 0.9; p = .415), while CPCr presented effect for condition (F = 13.4; p = .003; SN: 1.2 ± 0.1; PL: 1.4 ± 0.8 L), and no interaction (F = 1.2; p = .317). Total oxidative contribution were higher (p < .001) after SN (19.1 ± 3.4 L) than Placebo (16.7 ± 3.1 L), while total CPCr were lower (p = .002) after SN (12.4 ± 2.5 L) than PL (14.1 ± 2.6 L). Total energy contribution were not different between trials. Acute dose of SN supplementation improved oxidative contribution during HIIE, and reduced CPCr. Higher COXI is likely related to increased oxygen kinetics, while the lower CPCr might be related to the improved energetic efficiency.

Seven-day dietary nitrate supplementation clinically significantly improves basal macrovascular function in postmenopausal women: a randomized, placebo-controlled, double-blind, crossover clinical trial.

Introduction: Cardiovascular disease (CVD) is the leading cause of death in women, with increased risk following menopause. Dietary intake of beetroot juice and other plant-based nitrate-rich foods is a promising non-pharmacological strategy for increasing systemic nitric oxide and improving endothelial function in elderly populations. The purpose of this randomized, placebo-controlled, double-blind, crossover clinical trial was to determine the effects of short-term dietary nitrate (NO3 -) supplementation, in the form of beetroot juice, on resting macrovascular endothelial function and endothelial resistance to whole-arm ischemia-reperfusion (IR) injury in postmenopausal women at two distinct stages of menopause. Methods: Early-postmenopausal [1-6 years following their final menstrual period (FMP), n = 12] and late-postmenopausal (6+ years FMP, n = 12) women consumed nitrate-rich (400 mg NO3 -/70 mL) and nitrate-depleted beetroot juice (approximately 40 mg NO3 -/70 mL, placebo) daily for 7 days. Brachial artery flow-mediated dilation (FMD) was measured pre-supplementation (Day 0), and approximately 24 h after the last beetroot juice (BR) dose (Day 8, post-7-day BR). Consequently, FMD was measured immediately post-IR injury and 15 min later (recovery). Results: Results of the linear mixed-effects model revealed a significantly greater increase in resting FMD with 7 days of BRnitrate compared to BRplacebo (mean difference of 2.21, 95% CI [0.082, 4.34], p = 0.042); however, neither treatment blunted the decline in post-IR injury FMD in either postmenopausal group. Our results suggest that 7-day BRnitrate-mediated endothelial protection is lost within the 24-h period following the final dose of BRnitrate. Conclusion: Our findings demonstrate that nitrate-mediated postmenopausal endothelial protection is dependent on the timing of supplementation in relation to IR injury and chronobiological variations in dietary nitrate metabolism. Clinical trial registration: https://classic.clinicaltrials.gov/ct2/show/NCT03644472.

Effects of acute beetroot juice intake on performance, maximal oxygen uptake, and ventilatory efficiency in well-trained master rowers: a randomized, double-blinded crossover study.

BACKGROUND: Beetroot juice (BRJ) intake has been considered a practical nutritional strategy among well-trained athletes. This study aimed to assess the effects of BRJ intake on performance, cardiorespiratory and metabolic variables during a simulated 2000-meter rowing ergometer test in well-trained master rowers. METHOD: Ten well-trained male master rowers (30-48 years) participated in a randomized, double-blind, crossover design for 3 weeks. In the first week, a researcher explained all the experimental procedures to the participants. In the next two weeks, the participants were tested in 2 rowing ergometer sessions, separated from each other by a 7-day washout period. In both strictly identical sessions, the participants randomly drank BRJ or placebo (PL) 3 hours before the start of the tests. Subsequently, the participants carried out the 2000-meter rowing ergometer tests. Oxygen saturation and blood lactate measurements were performed before starting (pretest) and at the end of the test (posttest). Performance parameters and cardiorespiratory variables were recorded during the rowing ergometer test. RESULTS: An improvement in time trial performance was observed, with a mean difference of 4 seconds (90% confidence limits ± 3.10; p ≤ 0.05) compared to PL. Relative and absolute maximaloxygenuptakeV˙O2max increased (mean difference of 2.10 mL·kg-1·min-1, 90% confidence limits ± 1.80; mean difference of 0.16 L·min-1 90% confidence limits ± 0.11, respectively; p ≤ 0.05) compared to PL. No ergogenic effect was observed on ventilatory efficiency and blood lactate concentrations after BRJ intake. CONCLUSION: Acute BRJ intake may improve time trial performance as well as V˙O2max in well-trained master rowers. However, BRJ does not appear to improve ventilatory efficiency.

Effects of short-term dietary nitrate supplementation on exercise and coronary blood flow responses in patients with peripheral artery disease.

Background: Peripheral arterial disease (PAD) is a prevalent vascular disorder characterized by atherosclerotic occlusion of peripheral arteries, resulting in reduced blood flow to the lower extremities and poor walking ability. Older patients with PAD are also at a markedly increased risk of cardiovascular events, including myocardial infarction. Recent evidence indicates that inorganic nitrate supplementation, which is abundant in certain vegetables, augments nitric oxide (NO) bioavailability and may have beneficial effects on walking, blood pressure, and vascular function in patients with PAD. Objective: We sought to determine if short-term nitrate supplementation (via beetroot juice) improves peak treadmill time and coronary hyperemic responses to plantar flexion exercise relative to placebo (nitrate-depleted juice) in older patients with PAD. The primary endpoints were peak treadmill time and the peak coronary hyperemic response to plantar flexion exercise. Methods: Eleven PAD patients (52-80 yr.; 9 men/2 women; Fontaine stage II) were randomized (double-blind) to either nitrate-rich (Beet-IT, 0.3 g inorganic nitrate twice/day; BRnitrate) or nitrate-depleted (Beet-IT, 0.04 g inorganic nitrate twice/day, BRplacebo) beetroot juice for 4 to 6 days, followed by a washout of 7 to 14 days before crossing over to the other treatment. Patients completed graded plantar flexion exercise with their most symptomatic leg to fatigue, followed by isometric handgrip until volitional fatigue at 40% of maximum on day 4 of supplementation, and a treadmill test to peak exertion 1-2 days later while continuing supplementation. Hemodynamics and exercise tolerance, and coronary blood flow velocity (CBV) responses were measured. Results: Although peak walking time and claudication onset time during treadmill exercise did not differ significantly between BRplacebo and BRnitrate, the diastolic blood pressure response at the peak treadmill walking stage was significantly lower in the BRnitrate condition. Increases in CBV from baseline to peak plantar flexion exercise after BRplacebo and BRnitrate showed a trend for a greater increase in CBV at the peak workload of plantar flexion with BRnitrate (p = 0.06; Cohen's d = 0.56). Conclusion: Overall, these preliminary findings suggest that inorganic nitrate supplementation in PAD patients is safe, well-tolerated, and may improve the coronary hyperemic and blood pressure responses when their calf muscles are most predisposed to ischemia.Clinical trial registration:https://clinicaltrials.gov/, identifier NCT02553733.

Factors that Moderate the Effect of Nitrate Ingestion on Exercise Performance in Adults: A Systematic Review with Meta-Analyses and Meta-Regressions.

To identify how variables such as exercise condition, supplementation strategy, participant characteristics and demographics, and practices that control oral microbiota diversity could modify the effect of inorganic nitrate ingestion (as nitrate salt supplements, beetroot juice, and nitrate-rich vegetables) on exercise performance, we conducted a systematic review with meta-analysis. Studies were identified in PubMed, Embase, and Cochrane databases. Eligibility criteria included randomized controlled trials assessing the effect of inorganic nitrate on exercise performance in healthy adults. To assess the variation in effect size, we used meta-regression models for continuous variables and subgroup analysis for categorical variables. A total of 123 studies were included in this meta-analysis, comprising 1705 participants. Nitrate was effective for improving exercise performance (standardized mean difference [SMD]: 0.101; 95% CI: 0.051, 0.151, P <0.001, I2 = 0%), although nitrate salts supplementation was not as effective (P = 0.629) as ingestion via beetroot juice (P <0.001) or a high-nitrate diet (P = 0.005). Practices that control oral microbiota diversity influenced the nitrate effect, with practices harmful to oral bacteria decreasing the ergogenic effect of nitrate. The ingestion of nitrate was most effective for exercise lasting between 2 and 10 min (P <0.001). An inverse dose-response relation between the fraction of inspired oxygen and the effect size (coefficient: -0.045, 95% CI: -0.085, -0.005, P = 0.028) suggests that nitrate was more effective in increasingly hypoxic conditions. There was a dose-response relation for acute administration (P = 0.049). The most effective acute dose was between 5 and 14.9 mmol provided ≥150 min prior to exercise (P <0.001). An inverse dose-response for protocols ≥2 d was observed (P = 0.025), with the optimal dose between 5 and 9.9 mmol·d-1 (P <0.001). Nitrate, via beetroot juice or a high-nitrate diet, improved exercise performance, in particular, in sessions lasting between 2 and 10 min. Ingestion of 5-14.9 mmol⋅d-1 taken ≥150 min prior to exercise appears optimal for performance gains and athletes should be aware that practices controlling oral microbiota diversity may decrease the effect of nitrate.

Optimal Nitrate Supplementation in Phaeodactylum tricornutum Culture Medium Increases Biomass and Fucoxanthin Production.

Phaeodactylum tricornutum is a model diatom with numerous potential applications in the industry, including the production of high-value carotenoid pigments such as fucoxanthin. This compound is a potent antioxidant currently extracted mainly from brown macroalgae. Fucoxanthin exhibits several biological properties with well-known beneficial effects in the treatment and prevention of lifestyle-related diseases. P. tricornutum offers a valuable alternative to macroalgae for fucoxanthin production as it has a specific productivity that is 10-fold higher as compared with macroalgae. However, production processes still need to be optimised to become a cost-effective alternative. In this work, we investigated the optimal supplementation of nitrate in a cultivation medium that is currently used for P. tricornutum and how this nitrate concentration affects cell growth and fucoxanthin production. It has previously been shown that the addition of sodium nitrate increases productivity, but optimal conditions were not accurately determined. In this report, we observed that the continuous increase in nitrate concentration did not lead to an increase in biomass and fucoxanthin content, but there was rather a window of optimal values of nitrate that led to maximum growth and pigment production. These results are discussed considering both the scale up for industrial production and the profitability of the process, as well as the implications in the cell's metabolism and effects in fucoxanthin production.

The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis.

BACKGROUND: Nitrate supplementation is thought to improve performance in endurance sports. OBJECTIVE: To meta-analyze studies evaluating the effect of nitrate supplementation on endurance sports performance among adults. DATA SOURCES: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science and CINAHL without language restrictions. METHODS: We included studies that: 1) compared nitrate supplementation with placebo; 2) enrolled adults engaging in an endurance-based activity; and 3) reported a performance measure or surrogate physiologic outcome. We evaluated risk of bias using the Cochrane Collaboration tool and pooled data with a random-effects model. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to evaluate confidence in estimates. RESULTS: We included 73 studies (n = 1061). Nitrate supplementation improved power output (MD 4.6 watts, P < 0.0001), time to exhaustion (MD 25.3 s, P < 0.00001), and distance travelled (MD 163.7 m, P = 0.03). We found no significant difference on perceived exertion, time trial performance and work done. Nitrate supplementation decreased VO2 (MD - 0.04 L/min, P < 0.00001) but had no significant effect on VO2max or blood lactate levels. CONCLUSION: The available evidence suggests that dietary nitrate supplementation benefits performance-related outcomes for endurance sports.

The Effect of Beetroot Supplementation on High-Intensity Functional Training Performance.

Nitrate supplementation (NO3 -) has been shown to improve athletic performance for short-duration, vigorous activity, as well as long-duration, aerobic activity. The purpose was to explore the effects of beetroot supplementation (BR) on high-intensity functional training (HIFT) performance. Twenty-four HIFT participants (25 ± 6.5 years, 175.17 ± 8.1 cm, 84.94 ± 12.09 kg), who attended HIFT classes at least 3 days per week for the past 3 months, performed a benchmark performance test (5 rounds of a 400-m run followed by 15 overhead squats with a 95-lb (for males)/65-lb (for females) barbell). In a randomized order, 72 hrs apart, participants were tested under a control session and once after consuming 70 mL beetroot nitrate supplement, Beet It®, 2 hours prior to beginning the assigned benchmark test. For both benchmark tests, time to completion, pre- and post-exercise blood lactate levels, RPE, and pre-, during, and post-exercising heart rates were measured. There was no significant difference (p < 0.05) between the control (930 ± 192.6 sec) and supplement (952.8 ± 205.8 sec) on time to complete the performance test. Post-exercise blood lactate (11.14 ± 2.84 mm/dL) was not significantly different (p < 0.05) than the control (12.00 ± 2.53 mm/dL). Additionally, mean RPE for BR supplement (14.78 ± 2.50) was not significantly different (p < 0.05) than the control (14.92 ± 2.12). The short duration and high intensity of the workout, which included both anaerobic and aerobic components, may have mitigated the cardiovascular effect of beetroot nitrates unlike previous research that found significant positive effects between beetroot nitrates and exercise performance.

Role of Oral and Gut Microbiota in Dietary Nitrate Metabolism and Its Impact on Sports Performance.

Nitrate supplementation is an effective, evidence-based dietary strategy for enhancing sports performance. The effects of dietary nitrate seem to be mediated by the ability of oral bacteria to reduce nitrate to nitrite, thus increasing the levels of nitrite in circulation that may be further reduced to nitric oxide in the body. The gut microbiota has been recently implicated in sports performance by improving muscle function through the supply of certain metabolites. In this line, skeletal muscle can also serve as a reservoir of nitrate. Here we review the bacteria of the oral cavity involved in the reduction of nitrate to nitrite and the possible changes induced by nitrite and their effect on gastrointestinal balance and gut microbiota homeostasis. The potential role of gut bacteria in the reduction of nitrate to nitrite and as a supplier of the signaling molecule nitric oxide to the blood circulation and muscles has not been explored in any great detail.

Dietary nitrate reduces blood pressure and cerebral artery velocity fluctuations and improves cerebral autoregulation in transient ischemic attack patients.

Accentuated blood pressure (BP) fluctuation and low cerebral blood flow (CBF) response to CO2 increase the risk of transient ischemic attack (TIA) recurrence and stroke in TIA patients. Improving cardio- and cerebrovascular function may reduce stroke risk. We found dietary nitrate lowered dynamic blood pressure variability (BPV) in rats and improved cerebrovascular CO2 reactivity in healthy individuals. In 30 TIA patients, 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 study design. We hypothesized that 7-day dietary nitrate supplementation would decrease variabilities in BP and CBF and improve CBF-CO2 slope and cerebral autoregulation (CA). We assessed beat-to-beat middle cerebral artery blood velocity (MCAv; index of CBF) and BP at rest and during CO2 breathing. Transfer function analysis was performed on beat-to-beat MCAv and BP to determine CA parameters (gain, phase, and coherence). Irrespective of treatment, high- and low-frequency BP-MCAv gain and MCAv-CO2 slope increased 7 days following TIA onset, while low-frequency BPV decreased (P < 0.05 vs. baseline). At follow-up, dietary nitrate elevated plasma nitrate concentration by ~547% (P < 0.001) and moderately lowered BPV (d = 0.6, P = 0.011), MCAv variability (d = 0.7, P = 0.018), and BP-MCAv coherence (d = 0.7, P = 0.008) in the very-low-frequency range (0.02-0.07 Hz), while MCAv-CO2 slope and arterial stiffness were unaffected (P > 0.05). Concurrent with standard treatment, dietary nitrate supplementation reduces BP and CBF fluctuation and improves cerebral autoregulation in TIA patients, without affecting cerebrovascular CO2 reactivity.NEW & NOTEWORTHY We found dietary nitrate supplementation reduced blood pressure and brain blood flow fluctuations and improved the relationship between blood pressure and brain blood flow in transient ischemic attack patients. Meanwhile, dietary nitrate had no effects on the brain blood vessels' response to CO2. We attribute the improved brain blood flow stability to the improved myogenic control of blood pressure with dietary nitrate. Our findings indicate that dietary nitrate could be an effective strategy for stabilizing blood pressure and brain blood flow following transient ischemic attack.

Acute beetroot juice supplementation does not attenuate knee extensor exercise muscle fatigue in a healthy young population.

PURPOSE: The effect of acute nitrate supplementation on muscle fatigue is largely unknown. This study aimed to evaluate the effect of acute nitrate supplementation on muscle fatigue. METHODS: Thirty-five recreationally active subjects consumed 140 ml of beetroot (BR) juice (nitrate: 8 mmol·d-1) or placebo (PL) 12 and 2.5 hours before two exercise sessions. Peak torque was measured during 50 repetitions, at maximal effort, and during concentric knee extensions at 90°·s-1. Blood pressure (BP) was recorded pre- and post-exercise. RESULTS: Peak torque, maximum work, rate of fatigue, and rate of work fatigue were similar between the BR and PL conditions. Post-exercise diastolic BP (BR: 67.2 ± 9.8 vs. PL: 64.5 ± 7.9 mmHg, p < 0.05) and mean arterial pressure (BR: 91.6 ± 9.3 vs. PL: 88.8 ± 8.2 mmHg, p < 0.05) were higher with BR supplementation. CONCLUSION: These findings suggest that the acute intake of BR juice had no effect on knee extensor muscle strength or fatigue but increased BP in a healthy recreationally active population.

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.

Temporal stability of the rumen microbiota in beef cattle, and response to diet and supplements.

BACKGROUND: Dietary intake is known to be a driver of microbial community dynamics in ruminants. Beef cattle go through a finishing phase that typically includes very high concentrate ratios in their feed, with consequent effects on rumen metabolism including methane production. This longitudinal study was designed to measure dynamics of the rumen microbial community in response to the introduction of high concentrate diets fed to beef cattle during the finishing period. A cohort of 50 beef steers were fed either of two basal diet formulations consisting of approximately 10:90 or 50:50 forage:concentrate ratios respectively. Nitrate and oil rich supplements were also added either individually or in combination. Digesta samples were taken at time points over ~ 200 days during the finishing period of the cattle to measure the adaptation to the basal diet and long-term stability of the rumen microbiota. RESULTS: 16S rRNA gene amplicon libraries were prepared from 313 rumen digesta samples and analysed at a depth of 20,000 sequences per library. Bray Curtis dissimilarity with analysis of molecular variance (AMOVA) revealed highly significant (p < 0.001) differences in microbiota composition between cattle fed different basal diets, largely driven by reduction of fibre degrading microbial groups and increased relative abundance of an unclassified Gammaproteobacteria OTU in the high concentrate fed animals. Conversely, the forage-based diet was significantly associated with methanogenic archaea. Within basal diet groups, addition of the nitrate and combined supplements had lesser, although still significant, impacts on microbiota dissimilarity compared to pre-treatment time points and controls. Measurements of the response and stability of the microbial community over the time course of the experiment showed continuing adaptation up to 25 days in the high concentrate groups. After this time point, however, no significant variability was detected. CONCLUSIONS: High concentrate diets that are typically fed to finishing beef cattle can have a significant effect on the microbial community in the rumen. Inferred metabolic activity of the different microbial communities associated with each of the respective basal diets explained differences in methane and short chain fatty acid production between cattle. Longitudinal sampling revealed that once adapted to a change in diet, the rumen microbial community remains in a relatively stable alternate state.

Non-lethal nitrate supplementation enhances photosystem II efficiency in mixotrophic microalgae towards the synthesis of proteins and lipids.

The current study is aimed at understanding the effect of two different concentrations of nitrate (NaNO3) i.e., 2.94 mM (1X) and 8.82 mM (3X) on the productivity of Scenedesmus sp. in terms photosynthetic efficiency, growth, biomass and protein/lipid synthesis. The experiments were conducted by growing the microalgae in mixotrophic mode with a fixed dissolved organic carbon (110 mM). Chlorophyll a fluorescence fast kinetics parameter such as FV/FM, FM/FO, Pi_Abs, TRo/RC and ABS/RC depicted an improved PSII efficiency in 3X conditions. Higher nitrate concentration in BBM medium favored better assimilation of chlorophyll pigments, carbohydrates (160 mg/g), proteins (524 mg/g) and total lipids along with higher biomass (11.4 g/L). The microalgae cell growth, biomass and biochemical composition are significantly influenced by excess nitrates supplementation in the growth medium.

Effect of beetroot juice supplementation on 10-km performance in recreational runners.

The purpose of this study was to investigate the effects of chronic beetroot juice (BRJ) supplementation on 10-km running performance in recreational runners. In a double-blind, placebo-controlled, crossover-designed study, 14 male recreational runners (age, 27.8 ± 3.4 years) performed three 10-km running tests, at baseline and under the conditions of BRJ supplementation and placebo (PLA). Supplementation was administered for 3 days, and on the days of the assessments, the ingestion occurred 2 h before the test and consisted of a dose of 420 mL of BRJ in natura (8.4 mmol inorganic nitrate (NO3-)·day-1) or PLA with depleted NO3- (0.01 mmol NO3-·day-1). The mean velocity (MV) was calculated, and the following variables were determined: maximal heart rate, maximal rating of perceived exertion, blood glucose concentration (analyzed before and after the test), and lactate peak. There was no main effect between conditions regarding 10-km running time performance (BRJ: 50.1 ± 5.3 min; PLA: 51.0 ± 5.1 min; P = 0.391) and total MV (BRJ: 12.1 ± 1.3 km·h-1; PLA: 11.9 ± 1.2 km·h-1; P = 0.321) or in the other analyzed variables. The time to complete the first half of the test (5 km) was statistically lower in the BRJ group than in the PLA group (P = 0.027). In conclusion, chronic supplementation with BRJ increased MV in the first half of the test and improved the final test times of 10 of the 14 runners, although we did not find a statistically significant difference in the performance of the 10-km run.

Long-term effects of NO3- on the relationship between oxygen uptake and power after three weeks of supplemented HIHVT.

The aim of this study was to investigate the later effects of daily NO3- supplementation over 3 wk of training on the relationship between O2 uptake and power at different intensities with an incremental test (IT), a double-wingate test (WT), and an endurance capacity test at 80% Wmax (ECT) before and after the supplementation period. Seventeen male recreational athletes participated in this double-blind placebo (PL)-controlled study. Subjects participated in a 3-wk intermittent high-intensity, high-volume training period with 45 intervals of Wmax - 10 W and an active recovery period of 10 W in between with dietary NO3- (NaNO3) or placebo supplementation (NaCl) (both 8.5 mg·kg-1·day-1) on a cycle ergometer. During a training session, plasma [ NO3- ] ( P < 0.001) and plasma [ NO2- ] ( P < 0.01) were higher in nitrate (N), whereas in pre- and posttests mean plasma [ NO3- ] and [ NO2- ] were not different between groups. In the WT [48 h after cessation of supplementation (C)], the ratio between V̇o2 and power decreased in N ( P < 0.01) with no changes in PL. Endurance capacity (4-5 days after C) similarly increased in both groups ( P < 0.01). However, the total oxygen consumption decreased by 5% ( P < 0.01) in N, with no change in PL. The slope of V̇o2·W-1 in IT (5-7 days after C) decreased in N ( P < 0.01), whereas no changes were found in PL. During low- and moderate-intensity workloads, no changes and differences in V̇o2 could be detected. We conclude that nitrate supplementation causes a sustaining reduction of the oxygen cost per watt during exercise with a large recruitment of type II muscle fibers without affecting endurance capacity. NEW & NOTEWORTHY Because most studies focused on the acute effects of NO3- supplementation on exercise performance during a supplementation period, the sustainability of the effects of the NO3- supplementation remain unknown. We followed the development of V̇o2/W at different intensities during the first week after cessation of daily NO3- supplementation over 3 wk. The results indicate that NO3- supplementation has a long-term effect for at least 7 days after cessation during heavy all-out workloads without affecting endurance capacity.