Abstract:Background
Dietary inorganic nitrate (NO3−) is a polyatomic ion, which is present in large quantities in green leafy vegetables and beetroot, and has attracted considerable attention in recent years as a potential health-promoting dietary compound. Numerous small, well-controlled laboratory studies have reported beneficial health effects of inorganic NO3− consumption on blood pressure, endothelial function, cerebrovascular blood flow, cognitive function, and exercise performance. Translating th… Show more
“…Health status: The expert panel agreed that chronic dietary nitrate supplementation was ergogenic in healthy individuals, but did not reach consensus for acute supplementation being ergogenic in this population. The expert panel also felt that there was insufficient evidence, or were unable to reach consensus, for acute or chronic dietary nitrate supplementation being ergogenic in clinical populations, which is consistent with the mixed findings reported in the current literature for these cohorts (for a review, see [ 71 ]). It is important to highlight that only 58% of the expert panel reported having experience of using dietary nitrate with clinical populations, compared with 100% of the panel having experience with healthy or sporting populations.…”
Section: Discussionmentioning
confidence: 79%
“…Although these changes in the oral microbiome composition occurred alongside marked increases in NO biomarkers, it is important to note that the net oral nitrite production is influenced by a complex interplay between various nitrate- and nitrite-reducing microorganisms in the oral cavity. The influence of chronic dietary nitrate consumption on nitrate-reduction capacity of the oral microbial community in response to acute nitrate ingestion, and the impact of potential changes in relation to health and exercise performance, requires further exploration [ 71 ]. One recent study has shown positive associations between oral nitrate-reducing capacity and markers of aerobic fitness [ 80 ].…”
Section: Discussionmentioning
confidence: 99%
“…Similarly, they agreed that chronic dietary nitrate supplementation in dosages up to ~ 16 mmol/day does not increase risk of methaemoglobinaemia or hypotension. However, given that few studies have explored the long-term health (or other) effects of nitrate, additional well-controlled longitudinal studies are required to support these views [ 71 ]. A consensus was not reached for whether chronic supplementation increases risk of cancer or renal injury, the former of which has been a subject of much debate in the extant literature [ 71 ].…”
Introduction
Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be recommended as an ergogenic aid. Moreover, there is no consensus on the safe administration of dietary nitrate as an ergogenic aid. This study aimed to address these research gaps.
Methods
The modified Delphi technique was used to establish the views of 12 expert panel members on the use of dietary nitrate as an ergogenic aid. Over three iterative rounds (two via questionnaire and one via videoconferencing), the expert panel members voted on 222 statements relating to dietary nitrate as an ergogenic aid. Consensus was reached when > 80% of the panel provided the same answer (i.e. yes or no). Statements for which > 80% of the panel cast a vote of insufficient evidence were categorised as such and removed from further voting. These statements were subsequently used to identify directions for future research.
Results
The 12 panel members contributed to voting in all three rounds. A total of 39 statements (17.6%) reached consensus across the three rounds (20 yes, 19 no). In round one, 21 statements reached consensus (11 yes, 10 no). In round two, seven further statements reached consensus (4 yes, 3 no). In round three, an additional 11 statements reached consensus (5 yes, 6 no). The panel agreed that there was insufficient evidence for 134 (60.4%) of the statements, and were unable to agree on the outcome of the remaining statements.
Conclusions
This study provides information on the current expert consensus on dietary nitrate, which may be of value to athletes, coaches, practitioners and researchers. The effects of dietary nitrate appear to be diminished in individuals with a higher aerobic fitness (peak oxygen consumption [V̇O2peak] > 60 ml/kg/min), and therefore, aerobic fitness should be taken into account when considering use of dietary nitrate as an ergogenic aid. It is recommended that athletes looking to benefit from dietary nitrate supplementation should consume 8–16 mmol nitrate acutely or 4–16 mmol/day nitrate chronically (with the final dose ingested 2–4 h pre-exercise) to maximise ergogenic effects, taking into consideration that, from a safety perspective, athletes may be best advised to increase their intake of nitrate via vegetables and vegetable juices. Acute nitrate supplementation up to ~ 16 mmol is believed to be safe, although the safety of chronic nitrate supplementation requires further investigation. The expert panel agreed that there was insufficient evidence for most of the appraised statements, highlighting the need for future research in this area.
Graphical Abstract
“…Health status: The expert panel agreed that chronic dietary nitrate supplementation was ergogenic in healthy individuals, but did not reach consensus for acute supplementation being ergogenic in this population. The expert panel also felt that there was insufficient evidence, or were unable to reach consensus, for acute or chronic dietary nitrate supplementation being ergogenic in clinical populations, which is consistent with the mixed findings reported in the current literature for these cohorts (for a review, see [ 71 ]). It is important to highlight that only 58% of the expert panel reported having experience of using dietary nitrate with clinical populations, compared with 100% of the panel having experience with healthy or sporting populations.…”
Section: Discussionmentioning
confidence: 79%
“…Although these changes in the oral microbiome composition occurred alongside marked increases in NO biomarkers, it is important to note that the net oral nitrite production is influenced by a complex interplay between various nitrate- and nitrite-reducing microorganisms in the oral cavity. The influence of chronic dietary nitrate consumption on nitrate-reduction capacity of the oral microbial community in response to acute nitrate ingestion, and the impact of potential changes in relation to health and exercise performance, requires further exploration [ 71 ]. One recent study has shown positive associations between oral nitrate-reducing capacity and markers of aerobic fitness [ 80 ].…”
Section: Discussionmentioning
confidence: 99%
“…Similarly, they agreed that chronic dietary nitrate supplementation in dosages up to ~ 16 mmol/day does not increase risk of methaemoglobinaemia or hypotension. However, given that few studies have explored the long-term health (or other) effects of nitrate, additional well-controlled longitudinal studies are required to support these views [ 71 ]. A consensus was not reached for whether chronic supplementation increases risk of cancer or renal injury, the former of which has been a subject of much debate in the extant literature [ 71 ].…”
Introduction
Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be recommended as an ergogenic aid. Moreover, there is no consensus on the safe administration of dietary nitrate as an ergogenic aid. This study aimed to address these research gaps.
Methods
The modified Delphi technique was used to establish the views of 12 expert panel members on the use of dietary nitrate as an ergogenic aid. Over three iterative rounds (two via questionnaire and one via videoconferencing), the expert panel members voted on 222 statements relating to dietary nitrate as an ergogenic aid. Consensus was reached when > 80% of the panel provided the same answer (i.e. yes or no). Statements for which > 80% of the panel cast a vote of insufficient evidence were categorised as such and removed from further voting. These statements were subsequently used to identify directions for future research.
Results
The 12 panel members contributed to voting in all three rounds. A total of 39 statements (17.6%) reached consensus across the three rounds (20 yes, 19 no). In round one, 21 statements reached consensus (11 yes, 10 no). In round two, seven further statements reached consensus (4 yes, 3 no). In round three, an additional 11 statements reached consensus (5 yes, 6 no). The panel agreed that there was insufficient evidence for 134 (60.4%) of the statements, and were unable to agree on the outcome of the remaining statements.
Conclusions
This study provides information on the current expert consensus on dietary nitrate, which may be of value to athletes, coaches, practitioners and researchers. The effects of dietary nitrate appear to be diminished in individuals with a higher aerobic fitness (peak oxygen consumption [V̇O2peak] > 60 ml/kg/min), and therefore, aerobic fitness should be taken into account when considering use of dietary nitrate as an ergogenic aid. It is recommended that athletes looking to benefit from dietary nitrate supplementation should consume 8–16 mmol nitrate acutely or 4–16 mmol/day nitrate chronically (with the final dose ingested 2–4 h pre-exercise) to maximise ergogenic effects, taking into consideration that, from a safety perspective, athletes may be best advised to increase their intake of nitrate via vegetables and vegetable juices. Acute nitrate supplementation up to ~ 16 mmol is believed to be safe, although the safety of chronic nitrate supplementation requires further investigation. The expert panel agreed that there was insufficient evidence for most of the appraised statements, highlighting the need for future research in this area.
Graphical Abstract
“…Dietary nitrate therefore has the mechanistic potential to influence brain functions; however, observational and clinical trials, overall, have contrasting results (19,49) . A meta-analysis conducted in 2018 exploring the effects of dietary nitrate supplementation on cognition and CBF (19) found a lack of evidence for the benefits of dietary nitrate on both outcomes.…”
Section: Dietary Nitrate and Brain Healthmentioning
Dementia is a significant public health priority with approximately 55 million cases worldwide, and this number is predicted to quadruple by 2050. Adherence to a healthy diet and achieving optimal nutritional status are vital strategies to improve brain health. The importance of this area of research has been consolidated into the new term ‘nutritional psychiatry’. Dietary nitrate, closely associated with the intake of fruits and vegetables, is a compound that is increased in dietary patterns such as the Mediterranean and MIND diets and has protective effects on cognition and brain health. Nitrate is characterised by a complex metabolism and is the precursor of the nitrate–nitrite–nitric oxide (NO) pathway contributing to systemic NO generation. A higher intake of dietary nitrate has been linked to protective effects on vascular outcomes including blood pressure and endothelial function. However, the current evidence supporting the protective effects of dietary nitrate on brain health is less convincing. This article aims to provide a critical appraisal of the current evidence for dietary nitrate supplementation for improving brain health and provide suggestions for future research.
“…During the last decade, there has been an increased interest in investigating the health aspects of dietary nitrate supplementation (aimed to increase NO bioactivity) with a particular focus on cardiovascular regulation and exercise performance [3,4,11,12]. With this in mind, we previously hypothesized that dietary nitrate supplementation may be of benefit in boosting the activity of the nitrate-nitrite-NO pathway, thus restoring NO bioactivity in adult HD patients [10].…”
Nitric oxide (NO) contributes to maintaining normal cardiovascular and renal function. NO is generally formed enzymatically by NO synthase in the vascular endothelium. NO bioactivity can also be attributed to dietary intake of inorganic nitrate, which is abundant in our diet, especially in green leafy vegetables and beets. Ingested nitrate is reduced to nitrite by oral commensal bacteria and further to NO systemically. Previous studies have shown that dialysis, by means of removing nitrate and nitrite from the body, can reduce NO bioactivity. Hence, dietary intervention approaches aimed to boost the nitrate–nitrite–NO pathway may be of benefit in dialysis patients. The purpose of this study was to examine the kinetics of plasma nitrate and nitrite after a single intake of nitrate-rich concentrated beetroot juice (BJ) in adult hemodialysis (HD) patients and in healthy volunteers (HV). Eight HD patients and seven HV participated in this single center, randomized, single-blind, placebo-controlled, crossover study. Each participant received a sequential single administration of active BJ (70 mL 400 mg nitrate) and placebo BJ (70 mL 0 mg nitrate) in a random order separated by a washout period of seven days. For the kinetic analysis, blood samples were collected at different time-points before and up to 44 h after BJ intake. Compared with placebo, active BJ significantly increased plasma nitrate and nitrite levels both in HD patients and HV. The area under the curve and the maximal concentration of plasma nitrate, but not of nitrite, were significantly higher in HD patients as compared with HV. In both groups, active BJ ingestion did not affect blood pressure or plasma potassium levels. Both BJs were well tolerated in all participants with no adverse events reported. Our data provide useful information in planning dietary nitrate supplementation efficacy studies in patients with reduced NO bioactivity.
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