Dietary NO3- does not enhance endothelial dependent cutaneous vascular conductance in older women.

Prior work has yet to determine whether the reduction of dietary nitrate (NO3-) to NO, via the enterosalivary pathway, may modify cutaneous vascular conductance (CVC) responses to local heating in older women. Changes occurring with the transition to menopause related to hormonal flux, increased adiposity, and/or decreased physical activity may further compound the negative influence of aging on nitric oxide (NO)-dependent CVC. Herein, we characterized changes in NO-dependent CVC following acute ingestion of 140 mL of NO3--rich beetroot juice in 24 older women (age: 65 ± 5 y, BMI: 31.2 ± 3.7 kg/m2). Red blood cell (RBC) flux was measured continuously via laser-Doppler flowmetry on the dorsal aspect of the forearm during local skin heating to 39 °C/44 °C before and 3 h after NO3- ingestion. NO-dependent changes in CVC were calculated as RBC flux/mean arterial blood pressure at 39 °C and normalized as a proportion of maximal CVC at 44 °C (%CVCmax). Changes (Δ) in fractional exhaled NO (FeNO) following NO3- ingestion were used an index of NO bioavailability. Despite increased FeNO (+81 ± 70 %, P < 0.001), %CVCmax at 39 °C was reduced (-16 ± 10 %, P < 0.001) following NO3- ingestion. A greater reduction in %CVCmax was weakly to moderately associated with higher body fat% (r = 0.45 [0.05-0.72], P = 0.029), central adiposity% (r = 0.50 [0.13-0.75], P = 0.012), neutrophil% (r = 0.42 [0.02-0.70], P = 0.041), and higher neutrophil to lymphocyte ratio (r = 0.49 [0.11-0.75], P = 0.016). These findings demonstrate a single dose of dietary NO3- does not promote CVC responses to local heating in sedentary older women with overweight and obesity. Correlation with multiple biomarkers suggest systemic inflammation may be involved.

Influence of nitrate supplementation on motor unit activity during recovery following a sustained ischemic contraction in recreationally active young males.

PURPOSE: Dietary nitrate (NO3-) supplementation enhances muscle blood flow and metabolic efficiency in hypoxia, however, its efficacy on neuromuscular function and specifically, the effect on motor unit (MU) activity is less clear. We investigated whether NO3- supplementation affected MU activity following a 3 min sustained ischemic contraction and whether this is influenced by blood flow restriction (BFR) during the recovery period. METHOD: In a randomized, double-blinded, cross-over design, 14 males (mean ± SD, 25 ± 6 years) completed two trials following 5 days of supplementation with NO3--rich (NIT) or NO3--depleted (PLA) beetroot juice to modify plasma nitrite (NO2-) concentration (482 ± 92 vs. 198 ± 48 nmol·L-1, p < 0.001). Intramuscular electromyography was used to assess MU potential (MUP) size (duration and area) and mean firing rates (MUFR) during a 3 min submaximal (25% MVC) isometric contraction with BFR. These variables were also assessed during a 90 s recovery period with the first half completed with, and the second half completed without, BFR. RESULTS: The change in MUP area and MUFR, did not differ between conditions (all p > 0.05), but NIT elicited a reduction in MUP recovery time during brief isometric contractions (p < 0.001), and during recoveries with (p = 0.002) and without (p = 0.012) BFR. CONCLUSION: These novel observations improve understanding of the effects of NO3- on the recovery of neuromuscular function post-exercise and might have implications for recovery of muscle contractile function. TRIAL REGISTRATION: The study was registered on clinicaltrials.gov with ID of NCT05993715 on August 08, 2023.

Moderate dose of dietary nitrate improves skeletal muscle microvascular function in patients with peripheral artery disease.

Peripheral artery disease (PAD) is an atherosclerotic disease characterized by compromised lower-extremity blood flow that impairs walking ability. We showed that a moderate dose of dietary nitrate in the form of beetroot juice (BRJ, 0.11 mmol/kg) can improve macrovascular function and maximal walking distance in patients with PAD. However, its impacts on the microcirculation and autonomic nervous system have not been examined. Therefore, we investigated the impacts of this dose of dietary nitrate on skeletal muscle microvascular function and autonomic nervous system function and further related these measurements to 6-min walking distance, pain-free walking distance, and exercise recovery in patients with PAD. Patients with PAD (n = 10) ingested either BRJ or placebo in a randomized crossover design. Heart rate variability, skeletal muscle microvascular function, and 6-min walking distance were performed pre- and post-BRJ and placebo. There were significant group × time interactions (P < 0.05) for skeletal muscle microvascular function, 6-min walking distance, and exercise recovery, but no changes (P > 0.05) in heart rate variability or pain-free walking distance were noted. The BRJ group demonstrated improved skeletal muscle microvascular function (∆ 22.1 ± 7.5 %·min-1), longer 6-min walking distance (Δ 37.5 ± 9.1 m), and faster recovery post-exercise (Δ -15.3 ± 4.2 s). Furthermore, changes in skeletal muscle microvascular function were positively associated with changes in 6-min walking distance (r = 0.5) and pain-free walking distance (r = 0.6). These results suggest that a moderate dose of dietary nitrate may support microvascular function, which is related to improvements in walking distance and claudication in patients with PAD.

The effects of beetroot and nitrate supplementation on body composition: a GRADE-assessed systematic review and meta-analysis.

This systematic review and meta-analysis aimed to investigate the effects of beetroot (BR) or nitrate supplements on body composition indices. A systematic search was conducted for randomised controlled trials (RCT) published up to August 2022 among online databases including Scopus, PubMed/Medline, Web of Science and Embase. Meta-analyses were carried out using a random-effects model. The I2 index was used to assess the heterogeneity of RCT. A total of twelve RCT met the inclusion criteria for this meta-analysis. The pooled effect size of included studies indicated that BR or nitrate supplementation did not change body weight (weighted mean differences (WMD): -0·14 kg, 95 % CI -1·22, 1·51; P = 0·836; I2 = 0 %), BMI (WMD: -0·07 kg/m2, 95 % CI -0·19,0·03; P = 0·174, I2 = 0 %), fat mass (WMD: -0·26 kg, 95 % CI -1·51, 0·98; P = 0·677, I2 = 0 %), waist circumference (WMD: -0·28 cm, 95 % CI -2·30, 1·74; P = 0·786, I2 = 0 %), body fat percentage (WMD: 0·18 %, 95 % CI -0·62, 0·99; P = 0·651, I2 = 0 %), fat-free mass (WMD: 0·31 kg, 95 % CI -0·31, 1·94; P = 0·703, I2 = 0 %) and waist-to-hip ratio (WMD: 0, 95 % CI -0·01, 0·02; P = 0·676, I2 = 0 %). Subgroup analyses based on trial duration, BR or nitrate dose, study design, baseline BMI and athletic status (athlete v. non-athlete) demonstrated similar results. Certainty of evidence across outcomes ranged from low to moderate. This meta-analysis study suggests that BR or nitrate supplements cannot efficiently ameliorate body composition indices regardless of supplement dosage, trial duration and athletic status.

Moderate doses of dietary nitrate elicit greater effects on blood pressure and endothelial function than a high dose: A 13-week pilot study.

BACKGROUND & AIMS: Few studies have explored the prolonged effects of dietary nitrate on vascular health. This pilot study tested the effects of prolonged consumption (13 weeks) of a range of doses of dietary nitrate (NO3-), provided as beetroot juice (BJ), on blood pressure (BP) and endothelial function in overweight and obese older participants. METHODS AND RESULTS: Sixty-two overweight or obese older participants (60-75 years) were randomized to the following interventions: (1) high NO3- (2) medium NO3-, (3) low NO3-, or (4) placebo. Resting clinic and home BP were measured pre- and post-intervention. Laser Doppler iontophoresis was used to quantify changes in endothelial-dependent and independent microvascular blood flow. RESULTS: This pilot study showed that medium and low doses of NO3- were more effective in lowering resting-clinic SBP (P = 0.04 and, P = 0.03, respectively) than was PL. The lower doses of NO3- also resulted in significant increases in microvascular perfusion (medium, P = 0.02; low, P = 0.002) relative to baseline values. CONCLUSION: These findings indicate that supplementation with medium and low, but not high, doses of NO3- for 13 weeks had positive effects on BP and endothelial function in older overweight and obese adults. These findings require confirmation in larger studies.

Dietary nitrate supplementation enhances heavy load carriage performance in military cadets.

PURPOSE: To determine the effects of dietary nitrate (NO3-) supplementation on physiological responses, cognitive function, and performance during heavy load carriage in military cadets. METHODS: Ten healthy males (81.0 ± 6.5 kg; 180.0 ± 4.5 cm; 56.2 ± 3.7 ml·kg·min-1 VO2max) consumed 140 mL·d-1 of beetroot juice (BRJ; 12.8 mmol NO3-) or placebo (PL) for six d preceding an exercise trial, which consisted of 45 min of load carriage (55% body mass) at 4.83 km·h-1 and 1.5% grade, followed by a 1.6-km time-trial (TT) at 4% grade. Gas exchange, heart rate, and perceptual responses were assessed during constant-load exercise and the TT. Cognitive function was assessed immediately prior to, during, and post-exercise via the psychomotor vigilance test (PVT). RESULTS: Post-TT HR (188 ± 7.1 vs. 185 ± 7.4; d = 0.40; p = 0.03), mean tidal volume (2.15 ± 0.27 vs. 2.04 ± 0.23; p = 0.02; d = 0.47), and performance (770.9 ± 78.2 s vs. 809.8 ± 61.4 s; p = 0.03; d = 0.63) were increased during the TT with BRJ versus PL. There were no effects of BRJ on constant-load gas exchange or perceptual responses, and cognitive function was unchanged at all time points. CONCLUSION: BRJ supplementation improves heavy load carriage performance in military cadets possibly as a result of attenuated respiratory muscle fatigue, rather than enhanced exercise economy.

Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men.

PURPOSE: Dietary nitrate (NO3-) supplementation can lower systolic blood pressure (SBP) and improve exercise performance. Salivary flow rate (SFR) and pH are key determinants of oral NO3- reduction and purported to peak in the afternoon. We tested the hypotheses that NO3--rich beetroot juice (BR) would increase plasma [nitrite] ([NO2-]), lower SBP and improve exercise performance to a greater extent in the afternoon (AFT) compared to the morning (MORN) and evening (EVE). METHOD: Twelve males completed six experimental visits in a repeated-measures, crossover design. NO3--depleted beetroot juice (PL) or BR (~ 13 mmol NO3-) were ingested in the MORN, AFT and EVE. SFR and pH, salivary and plasma [NO3-] and [NO2-], brachial SBP and central SBP were measured pre and post supplementation. A severe-intensity exercise tolerance test was completed to determine cycling time to exhaustion (TTE). RESULTS: There were no between-condition differences in mean SFR or salivary pH. The elevation in plasma [NO2-] after BR ingestion was not different between BR-MORN, BR-AFT and BR-EVE. Brachial SBP was unchanged following BR supplementation in all conditions. Central SBP was reduced in BR-MORN (- 3 ± 4 mmHg), BR-AFT (- 4 ± 3 mmHg), and BR-EVE (- 2 ± 3 mmHg), with no differences between timepoints. TTE was not different between BR and PL at any timepoint. CONCLUSION: Acute BR supplementation was ineffective at improving TTE and brachial SBP and similarly effective at increasing plasma [NO2-] and lowering central SBP across the day, which may have implications for informing NO3- supplementation strategies.

Relationship between the Consumption of Fermented Red Beetroot Juice and Levels of Perfluoroalkyl Substances in the Human Body's Fluids and Blood Parameters.

Per- and polyfluoroalkyl substances (PFASs) are a group of fluorinated, organic, man-made chemicals; they do not occur naturally in the environment. This study aimed to determine the profile and content of PFASs in the volunteers' blood plasma and urine after the consumption of fermented red beetroot juice and then correlated it with the blood parameters. Over 42 days, 24 healthy volunteers ingested 200 mL/60 kg of body weight of fermented red beetroot juice. PFASs were analyzed using the micro-HPLC-MS/MS method. Five perfluoroalkyl substances were found in the volunteers' body fluids. After consuming the juice, it was discovered that regarding the perfluorocarboxylic acids, a downward trend was observed, while regarding the perfluoroalkane sulfonates, and their plasma content showed a statistically significant upward trend. Analysis of the hematology parameters indicated that the intake of fermented red beetroot juice showed a significant decrease in mean corpuscular volume (MCV), platelets concentration, mean platelet volume (MPV), platelet large cell ratio (P-LCR) at the significance level p < 0.01, and hematocrit (p < 0.05). On the other hand, the dietary intervention also indicated a significant (p < 0.01) increase in corpuscular/cellular hemoglobin concentration (MCHC). In the case of blood biochemistry, no significant change was observed in the blood samples after the intake of the fermented beetroot juice. However, a decreasing tendency of total cholesterol and low-density lipoprotein concentration (LDL-C) was observed. Based on the presented results, there is a need to analyze and monitor health-promoting food regarding undesirable substances and their impact on consumer health.

Influence of High-Pressure Homogenization on the Physicochemical Properties and Betalain Pigments of Red Beetroot (Beta vulgaris L.) Juice.

High-pressure homogenization (HPH) is considered an innovative and modern method of processing and preserving liquid and semi-liquid foods. The aim of this research was to examine the impact of HPH processing on the content of betalain pigments and physicochemical properties of beetroot juice. Combinations of the following HPH parameters were tested: the pressure used (50, 100, 140 MPa), the number of cycles (1 and 3) and the applied cooling or no cooling. The physicochemical analysis of the obtained beetroot juices was based on the determination of the extract, acidity, turbidity, viscosity and color values. Use of higher pressures and a greater number of cycles reduces the turbidity (NTU) of the juice. Moreover, in order to maintain the highest possible extract content and a slight color change of the beetroot juice, it was crucial to perform sample cooling after the HPH process. The quantitative and qualitative profiles of betalains have been also determined in the juices. In terms of the content of betacyanins and betaxanthins, the highest values were found in untreated juice at 75.3 mg and 24.8 mg per 100 mL, respectively. The high-pressure homogenization process resulted in a decrease in the content of betacyanins in the range of 8.5-20.2% and of betaxanthins in the range of 6.5-15.0%, depending on the parameters used. Studies have shown that that the number of cycles was irrelevant, but an increase in pressure from 50 MPa to 100 or 140 MPa had a negative effect on pigment content. Additionally, juice cooling significantly limits the degradation of betalains in beetroot juice.

Acute dietary nitrate supplementation does not change venous volume and compliance in healthy young adults.

In this crossover study, we investigated the influence of inorganic nitrate ([Formula: see text]) supplementation on venous volume and compliance in the resting forearm and calf. Twenty healthy young adults were assigned to receive an [Formula: see text]-rich beverage [beetroot juice (BRJ): 140 mL; ∼8 mmol [Formula: see text]] or an [Formula: see text]-depleted control beverage [prune juice (CON): 166 mL; < 0.01 mmol [Formula: see text]). Two hours after consuming the allocated beverage, each participant rested in the supine position for 20 min. Cuffs were then placed around the right upper arm and right thigh, inflated to 60 mmHg for 8 min, and then decreased to 0 mmHg at a rate of 1 mmHg/s. During inflation and deflation of cuff pressure, changes in venous volume in the forearm and calf were measured by venous occlusion plethysmography. Venous compliance was calculated as the numerical derivative of the cuff pressure-venous volume curve in the limbs. The plasma [Formula: see text] concentration was elevated by intake of BRJ (before, 15.5 ± 5.8 µM; after, 572.0 ± 116.1 µM, P < 0.05) but not by CON (before, 14.8 ± 7.2 µM; after, 15.3 ± 7.4 µM, P > 0.05). On the other hand, there was no significant difference in venous volume or compliance in the forearm or calf between BRJ and CON. These findings suggest that although acute inorganic NO3- supplementation may enhance the activity of nitric oxide (NO) via nitrite → NO pathway, it does not influence venous volume or compliance in the limbs in healthy young adults.

Strategies targeting the NO pathway to counteract extra-pulmonary manifestations of COPD: A systematic review and meta-analysis.

The clinical symptoms of chronic obstructive pulmonary disease (COPD) disease are accompanied by severely debilitating extra-pulmonary manifestations, including vascular dysfunction and hypertension. This systematic review evaluated the current evidence for several therapeutic interventions, targeting the nitric oxide (NO) pathway on hemodynamics and, secondarily, exercise capacity in patients with COPD. A comprehensive search on COPD and NO donors was performed on online databases. Of 934 initially found manuscripts, 27 were included in the review, and 16 in the meta-analysis. The analysis indicated inconsistent effects of dietary nitrate supplementation on exercise tolerance in COPD patients. Dietary nitrate supplementation decreased systolic (-3.7 ± 4.3 mmHg; p = 0.10) and diastolic blood pressure (BP; -2.6 ± 3.2 mmHg; p = 0.05) compared with placebo. When restricted to acute studies, a clinically relevant BP lowering effect of nitrate supplementation during diastole was observed (-4.7 ± 3.2 mmHg; n = 5; p = 0.05). In contrast, inhaled NO (iNO) at doses <20 ppm (+9.2 ± 11.3 mmHg) and 25-40 ppm (-5±2 mmHg) resulted in inconsistent effects on PaO2 (p = 0.48). Data on the effect of iNO on exercise capacity were too limited and inconsistent, but preliminary evidence suggests a possible benefit of iNO on pulmonary vascular resistance during exercise in severe COPD patients. Overall, the effects of acute dietary nitrate supplementation on BP may be of clinical relevance as an adjunct therapy and deserve further investigation in large sample size studies of COPD patients with and without cardiovascular comorbidities. iNO exerted inconsistent physiological effects, with the use of high doses posing safety risks.

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

BACKGROUND: Nitrate (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. PURPOSE: To 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). METHODS: Sixteen 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. RESULTS: Plasma 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). CONCLUSIONS: These 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.

The effect of eight weeks beetroot juice supplement on aerobic, anaerobic power, and field performance of soccer players.

The purpose of the study investigated the effect of eight weeks of soccer training with beetroot juice supplement on aerobic power, anaerobic power, and field performance of soccer players. This is experimental research, by the control group in pre and post-test. The statistical population was male soccer players. Forty subjects were randomly divided into four groups including the exercise group (EX) the exercise group with beetroot juice supplement (EX&BRJS) the beetroot juice supplement group (BRJS), and the control group (C). Aerobic power, anaerobic threshold, and respiratory exchange ratio, measured by the gas analyser (Cosmed), anaerobic power (peak, mean power), and fatigue index, by Wingate cycle test (Monark, 839), and field performance by (Bangsbo, field test performance). The statistical methods include the Kolmogorov-Smirnov, Levin, covariance (ANCOVA), and pair comparison with Bonferroni test. The results showed eight weeks' of soccer training with beetroot juice supplement, significantly changed aerobic power, respiratory exchange ratio, anaerobic threshold, anaerobic power, field performance, and fatigue index (P ≤ 0.05). Additionally, in all variables, the paired comparison showed that the EX&BRJS group progressed more than all other condition groups. The soccer athletes may use beetroot juice supplements along with soccer exercises to improve aerobic and anaerobic power and field performance.

Body mass-normalized moderate dose of dietary nitrate intake improves endothelial function and walking capacity in patients with peripheral artery disease.

Peripheral artery disease (PAD) is characterized by the accumulation of atherosclerotic plaques in the lower extremity conduit arteries, which impairs blood flow and walking capacity. Dietary nitrate has been used to reduce blood pressure (BP) and improve walking capacity in PAD. However, a standardized dose for PAD has not been determined. Therefore, we sought to determine the effects of a body mass-normalized moderate dose of nitrate (0.11 mmol nitrate/kg) as beetroot juice on serum nitrate/nitrite, vascular function, walking capacity, and tissue oxygen utilization capacity in patients with PAD. A total of 11 patients with PAD received either nitrate supplement or placebo in a randomized crossover design. Total serum nitrate/nitrite, resting BP, brachial and popliteal artery endothelial function (flow-mediated dilation, FMD), arterial stiffness (pulse-wave velocity, PWV), augmentation index (AIx), maximal walking distance and time, claudication onset time, and skeletal muscle oxygen utilization were measured pre- and postnitrate and placebo intake. There were significant group × time interactions (P < 0.05) for serum nitrate/nitrite, FMD, BP, walking distance and time, and skeletal muscle oxygen utilization. The nitrate group showed significantly increased serum nitrate/nitrite (Δ1.32 µM), increased brachial and popliteal FMD (Δ1.3% and Δ1.7%, respectively), reduced peripheral and central systolic BP (Δ-4.7 mmHg and Δ-8.2 mmHg, respectively), increased maximal walking distance (Δ92.7 m) and time (Δ56.3 s), and reduced deoxygenated hemoglobin during walking. There were no changes in PWV, AIx, or claudication (P > 0.05). These results indicate that a body-mass normalized moderate dose of nitrate may be effective and safe for reducing BP, improving endothelial function, and improving walking capacity in patients with PAD.

Multiple-day high-dose beetroot juice supplementation does not improve pulmonary or muscle deoxygenation kinetics of well-trained cyclists in normoxia and hypoxia.

Dietary nitrate (NO3-) supplementation via beetroot juice (BR) has been reported to lower oxygen cost (i.e., increased exercise efficiency) and speed up oxygen uptake (VO2) kinetics in untrained and moderately trained individuals, particularly during conditions of low oxygen availability (i.e., hypoxia). However, the effects of multiple-day, high dose (12.4 mmol NO3- per day) BR supplementation on exercise efficiency and VO2 kinetics during normoxia and hypoxia in well-trained individuals are not resolved. In a double-blinded, randomized crossover study, 12 well-trained cyclists (66.4 ± 5.3 ml min-1∙kg-1) completed three transitions from rest to moderate-intensity (~70% of gas exchange threshold) cycling in hypoxia and normoxia with supplementation of BR or nitrate-depleted BR as placebo. Continuous measures of VO2 and muscle (vastus lateralis) deoxygenation (ΔHHb, using near-infrared spectroscopy) were acquired during all transitions. Kinetics of VO2 and deoxygenation (ΔHHb) were modeled using mono-exponential functions. Our results showed that BR supplementation did not alter the primary time constant for VO2 or ΔHHb during the transition from rest to moderate-intensity cycling. While BR supplementation lowered the amplitude of the VO2 response (2.1%, p = 0.038), BR did not alter steady state VO2 derived from the fit (p = 0.258), raw VO2 data (p = 0.231), moderate intensity exercise efficiency (p = 0.333) nor steady state ΔHHb (p = 0.224). Altogether, these results demonstrate that multiple-day, high-dose BR supplementation does not alter exercise efficiency or oxygen uptake kinetics during normoxia and hypoxia in well-trained athletes.

Marching to the Beet: The effect of dietary nitrate supplementation on high altitude exercise performance and adaptation during a military trekking expedition.

PURPOSE: The aim was to investigate the effect of dietary nitrate supplementation (in the form of beetroot juice, BRJ) for 20 days on salivary nitrite (a potential precursor of bioactive nitric oxide), exercise performance and high altitude (HA) acclimatisation in field conditions (hypobaric hypoxia). METHODS: This was a single-blinded randomised control study of 22 healthy adult participants (12 men, 10 women, mean age 28 ± 12 years) across a HA military expedition. Participants were randomised pre-ascent to receive two 70 ml dose per day of either BRJ (~12.5 mmol nitrate per day; n = 11) or non-nitrate calorie matched control (n = 11). Participants ingested supplement doses daily, beginning 3 days prior to departure and continued until the highest sleeping altitude (4800 m) reached on day 17 of the expedition. Data were collected at baseline (44 m altitude), at 2350 m (day 9), 3400 m (day 12) and 4800 m (day 17). RESULTS: BRJ enhanced the salivary levels of nitrite (p = 0.007). There was a significant decrease in peripheral oxygen saturation and there were increases in heart rate, diastolic blood pressure, and rating of perceived exertion with increasing altitude (p=<0.001). Harvard Step Test fitness scores significantly declined at 4800 m in the control group (p = 0.003) compared with baseline. In contrast, there was no decline in fitness scores at 4800 m compared with baseline (p = 0.26) in the BRJ group. Heart rate recovery speed following exercise at 4800 m was significantly prolonged in the control group (p=<0.01) but was unchanged in the BRJ group (p = 0.61). BRJ did not affect the burden of HA illness (p = 1.00). CONCLUSIONS: BRJ increases salivary nitrite levels and ameliorates the decline in fitness at altitude but does not affect the occurrence of HA illness.

The benefits and risks of beetroot juice consumption: a systematic review.

Beetroot juice (BRJ) has become increasingly popular amongst athletes aiming to improve sport performances. BRJ contains high concentrations of nitrate, which can be converted into nitric oxide (NO) after consumption. NO has various functions in the human body, including a vasodilatory effect, which reduces blood pressure and increases oxygen- and nutrient delivery to various organs. These effects indicate that BRJ may have relevant applications in prevention and treatment of cardiovascular disease. Furthermore, the consumption of BRJ also has an impact on oxygen delivery to skeletal muscles, muscle efficiency, tolerance and endurance and may thus have a positive impact on sports performances. Aside from the beneficial aspects of BRJ consumption, there may also be potential health risks. Drinking BRJ may easily increase nitrate intake above the acceptable daily intake, which is known to stimulate the endogenous formation of N-nitroso compounds (NOC's), a class of compounds that is known to be carcinogenic and that may also induce several other adverse effects. Compared to studies on the beneficial effects, the amount of data and literature on the negative effects of BRJ is rather limited, and should be increased in order to perform a balanced risk assessment.

Dietary nitrate prevents progression of carotid subclinical atherosclerosis through blood pressure-independent mechanisms in patients with or at risk of type 2 diabetes mellitus.

AIMS: To test if 6 months' intervention with dietary nitrate and spironolactone could affect carotid subclinical atherosclerosis and stiffness, respectively, vs. placebo/doxazosin, to control for blood pressure (BP). METHODS: A subgroup of participants in our double-blind, randomized-controlled, factorial VaSera trial had carotid imaging. Patients with hypertension and with/at risk of type 2 diabetes were randomized to active nitrate-containing beetroot juice or placebo nitrate-depleted juice, and spironolactone or doxazosin. Vascular ultrasound for carotid diameter (CD, mm) and intima-media thickness (CIMT, mm) was performed at baseline, 3- and 6-months. Carotid local stiffness (CS, m/s) was estimated from aortic pulse pressure (Arteriograph) and carotid lumen area. Data were analysed by modified intention to treat and using mixed-model effect, adjusted for confounders. RESULTS: In total, 93 subjects had a baseline evaluation and 86% had follow-up data. No statistical interactions occurred between the juice and drug arms and BP was similar between the juices and between the drugs. Nitrate-containing vs. placebo juice significantly lowered CIMT (-0.06 [95% confidence interval -0.12, -0.01], P = .034), an overall difference of ~8% relative to baseline; but had no effect on CD or CS. Doxazosin appeared to reduce CS from baseline (-0.34 [-0.62, -0.06]) however, no difference was detected vs. spironolactone (-0.15 [-0.46, 0.16]). No differences were detected between spironolactone or doxazosin on CIMT and CD. CONCLUSIONS: Our results show that 6 months' intervention with dietary nitrate influences vascular remodelling, but not carotid stiffness or diameter. Neither spironolactone nor doxazosin had a BP-independent effect on carotid structure and function.

Effects of acute dietary nitrate supplementation on cold-induced vasodilation in healthy males.

PURPOSE: Cold-induced vasodilation (CIVD) is a paradoxical rise in blood flow to the digits that occur during prolonged cold exposure. CIVD is thought to occur through active vasodilation and/or sympathetic withdrawal, where nitric oxide (NO) may play a key role in mediating these mechanisms. Beetroot juice (BRJ) is high in dietary nitrate (NO3-) which undergoes sequential reduction to nitrite (NO2-) and subsequently NO. Using a double-blind, randomized, crossover design, we examined the effect of acute BRJ supplementation on the CIVD response in 10 healthy males. METHODS: Participants had a resting blood pressure measurement taken prior to ingesting 140 mL of nitrate-rich BRJ (13 mmol NO3-) or a NO3--free placebo (PLA). After 2 h, participants immersed their hand in neutral water (~ 35 °C) for 10 min of baseline before cold water immersion (~ 8 °C) for 30 min. Laser-Doppler fluxmetry and skin temperature were measured continuously on the digits. RESULTS: Compared to PLA (100 ± 3 mmHg), acute BRJ supplementation significantly reduced mean arterial pressure at -30 min (96 ± 2 mmHg; p = 0.007) and 0 min (94 ± 2 mmHg; p = 0.008). Acute BRJ supplementation had no effect on Laser-Doppler fluxmetry during CIVD (expressed as cutaneous vascular conductance) measured as area under the curve (BRJ: 843 ± 148 PU mmHg-1 s; PLA: 1086 ± 333 PU mmHg-1 s), amplitude (BRJ: 0.60 ± 0.12 PU mmHg-1; PLA: 0.69 ± 0.14 PU mmHg-1), and duration (BRJ: 895 ± 60 s; PLA: 894 ± 46 s). CONCLUSION: Acute BRJ supplementation does not augment the CIVD response in healthy males.

Influence of Dietary Nitrate Supplementation on High-Intensity Intermittent Running Performance at Different Doses of Normobaric Hypoxia in Endurance-Trained Males.

This study investigated whether supplementation with nitrate-rich beetroot juice (BR) can improve high-intensity intermittent running performance in trained males in normoxia and different doses of normobaric hypoxia. Eight endurance-trained males (V˙O2peak, 62 ± 6 ml·kg-1·min-1) completed repeated 90 s intervals at 110% of peak treadmill velocity, from an initial step incremental test, interspersed by 60 s of passive recovery until exhaustion (Tlim). Participants completed the first three experimental trials during days 3, 5, and 7 of BR or nitrate-depleted beetroot juice (PLA) supplementation and completed the remaining experimental visits on the alternative supplement following at least 7 days of washout. The fraction of inspired oxygen during visits 1-3 was either 0.209, 0.182, or 0.157, equivalent to an altitude of 0, 1,200, and 2,400 m, respectively, and this order was replicated on visits 4-6. Arterial oxygen saturation declined dose dependently as fraction of inspired oxygen was lowered (p < .05). Plasma nitrite concentration was higher pre- and postexercise after BR compared with PLA supplementation (p < .05). There was no difference in Tlim between PLA and BR at 0 m (445 [324, 508] and 410 [368, 548] s); 1,200 m (341 [270, 390] and 332 [314, 356] s); or 2,400 m (233 [177, 373] and 251 [221, 323] s) (median and [interquartile range]; p > .05). The findings from this study suggest that short-term BR supplementation does not improve high-intensity intermittent running performance in endurance-trained males in normoxia or at doses of normobaric hypoxia that correspond to altitudes at which athletes typically train while on altitude training camps.