Most of you who know me, may recall how often I am promoting the use of Raw Beetroot, as a means of dealing w/ fatigue by obtaining more energy...
Explaining precisely "How & Why" Raw Beetroot delivers beneficial outcomes for some, while NOT in others, unfortunately still remains a mystery to this intrepid, curious mind...
However, & not to be deterred, Please feel FREE to scan over and into this entire research STUDY, as it once more confirms that which I am already very well aware of... Raw Beetroot (Nectar & powdered extract), have the ability to enhance endurance levels during exercise...
Apparently, the raw Nitric oxide (NO3), helps to open the flow within our arteries, and this in turn delivers ever greater amounts of Oxygen into our blood stream & muscles, providing greater levels of energy...
There is some suggestion that this works best for those of us who are NOT, (I repeat – ARE NOT), elite athletes...
That simply means I am covered by this finding... YAY!!!
Ideally, I like to drink my 300-500ml 60-90mins' before exercise, & to take my drink every day is when it seems to work best of all... When I skip a couple of days, well I can really feel the difference in my overall lack of energy and general disposition etc.
Anyways, each of you must decide if this works for you... I am simply trying to share some of my knowledge on the subject of Raw Beetroot...
Naturally, I shall be interested to learn if any of you, (like me), have discovered the ongoing merits of Raw Beetroot...
Best wishes all...
Steve
ABBREVIATIONS:
GXT:
graded exercise test
IGXT:
intermittent graded exercise test
ITT:
intermittent time-trial
ITTE:
intermittent time to exhaustion
k:
number of trials
km:
kilometre
n:
sample size
NO2 - :
nitrite
NO3 - :
nitrate
PL:
performance level
Qb :
between-group Q-statistic
SMD:
standardised mean difference (Hedge’s g)
TT:
time-trial
TTE:
time to exhaustion
BACKGROUND:
Nitric oxide (NO) is a signalling molecule that is involved in numerous physiological processes including skeletal muscle contraction [1], endothelial function [2], mitochondrial biogenesis and respiration [3], muscle repair [4] and antioxidant defences [5,6,7]. Given these functions are important during exercise, particularly aerobic exercise, there has been considerable interest in enhancing NO production to improve endurance exercise performance. Specifically, increased synthesis of NO is proposed to reduce the oxygen cost of ATP resynthesis, lower the ATP cost of cross-bridge formation and promote vasodilation, thereby enhancing skeletal muscle blood flow and oxygen perfusion which may speed oxygen uptake kinetics [8]. These effects may translate to increased endurance exercise performance by improving exercise efficiency, decreasing the oxygen deficit at exercise onset and reducing the V̇O2 slow component [9].
NO is synthesised through two pathways, one of which is nitric oxide synthase (NOS)-dependent and one which is independent of NOS. NO is synthesised via the NOS-dependent pathway from L-arginine and oxygen in a reaction that is catalysed by various NOS enzymes, including endothelial nitric oxide synthase (eNOS). L-citrulline, an α-amino acid, also contributes to NO synthesis through this NOS-dependent pathway via its conversion to L-arginine. Polyphenols may enhance NO production by increasing eNOS expression and activity [10] and promote NO bioavailability via their antioxidant effects protecting NO from breakdown by reactive oxygen species (ROS). Within the NOS-independent pathway, nitrate (NO3-) is reduced to nitrite (NO2-) and then NO. Thus, it is proposed that NO availability may be improved by increasing the availability of NO3-, NO2-, L-arginine, L-citrulline, or polyphenols. Such changes in NO bioavailability are typically evaluated by plasma or urine NO3- and NO2-, as these are end products of endogenous NO production, but can also be inferred via measures of vascular function such as flow-mediated dilation (FMD).
In addition to the effects of polyphenols on NO synthesis via the NOS-independent pathway, their antioxidant properties have also been proposed to promote exercise performance by helping to maintain redox balance [11]. While the increase in ROS during exercise is an important signalling component that can facilitate acute responses and chronic adaptations to exercise, an imbalance between oxidative stress and antioxidant capacity may lead to impairment in blood flow, calcium handling and sensitivity, and central neural drive [11,12,13]. These derangements may contribute to the development of fatigue during exercise, so increasing antioxidant capacity may assist in inhibiting the onset of fatigue and enhance athletic performance. Thus, increased consumption of dietary polyphenols may enhance endurance exercise performance through effects on the NOS-dependent pathway and antioxidant capacity during exercise.
Augmentation of NO synthesis and bioavailability has been attempted by increasing the dietary intake of NO precursors. NO3- is abundant in beetroot and green leafy vegetables such as lettuce and spinach [14] and L-arginine is found in seafood, nuts, seeds, soy protein isolate and watermelon. Watermelon is also a rich source of L-citrulline, while fruits, vegetables, tea, coffee and cocoa are rich sources of polyphenols [15]. NO2-can be found in some fruits and vegetables, with more pronounced concentrations found in processed meats where it is used as an additive [16]. Many foods contain a combination of these nitric oxide precursors, as well as other antioxidant components such as vitamins, minerals and carotenoids, with interactions between these various phytochemicals and food sources potentially resulting in varied responses to specific foods and/or combinations of foods [17,18,19].
There appear to be considerable inter-individual differences in bioavailability in response to consumption of polyphenols [20] and NO3- [21, 22]. Several factors may influence the content and bioavailability of polyphenols in foods, such as storage and processing methods [23], the food matrix, and in particular, the profile of specific polyphenol subclasses (e.g. anthocyanidins vs quercetin) which vary significantly in their absorptive characteristics [20, 24]. Bioavailability is also affected by background diet, genetic factors, and particularly intestinal microbiota, as most polyphenols are catabolised by bacteria in the large intestine and the catabolites then enter the circulation and exert antioxidant effects [19, 25]. Similarly, the composition of NO3--rich food sources and microflora of the oral and gut microbiome may impact the bioavailability of NO3- from NO3--rich foods [22]. While increasing NO production may improve endurance exercise performance, performance effects may also be influenced by sex and fitness-related differences in NO synthesis [26, 27], vascular function [28, 29] and oxidative damage [30, 31]. Thus it is important to evaluate whether the effects of consuming foods that increase NO production on endurance exercise performance are influenced by these individual factors, as well as other parameters such as type of exercise performance test performed, the intensity at which the test is performed, and the dose and duration of consumption of NO precursors.
The primary aim of this systematic review and meta-analysis was to evaluate whether consumption of foods rich in precursors of NO synthesis improves endurance exercise performance. A secondary aim was to determine the effect of dose and duration of consumption of foods rich in NO precursors, participant characteristics (fitness and sex) and exercise test parameters (type and intensity) on exercise performance.
ARTICLE CONCLUSION (Verbatim):
Consumption of foods rich in NO3- and polyphenols may provide trivial beneficial effects for endurance exercise performance, while consumption of foods rich in L-citrulline, currently limited only to studies of watermelon juice, does not appear to affect performance.
Beetroot juice has been extensively studied and its NO3- content confers ergogenic effects in various exercise types in populations that are not considered well-trained.
Other food sources of NO3- require further investigation of their ergogenic capacity. Food-derived polyphenols appear to have the potential to enhance TT performance to a similar extent as beetroot juice, although more research is needed regarding its efficacy for use in highly trained athletes.
No effects were evident for the consumption of polyphenols from New Zealand blackcurrant, cocoa, ginseng, green tea and raisins, but significant benefits were shown for the consumption of grape, beetroot (NO3--depleted), French maritime pine, Montmorency cherry and pomegranate across multiple studies.
However, caution should be exercised in translating these ergogenic effects to other food sources of polyphenols, as there seems to be considerable variation in the effects between foods that cannot be attributed to differences in total phenolic content or key polyphenolic compounds.
Distinct responses to NO3- and polyphenol supplementation were also observed between males and females, with females not demonstrating any benefit for exercise performance. This may be due to sex-based differences in nitric oxide synthesis, vascular function and oxidative stress, and/or the limited number of female studies and the training status of the participants.
Future studies should evaluate effects of NO3- and polyphenol consumption on training performance and adaptations, as well as optimising protocols for consuming polyphenol-rich foods, and establishing the individual and test-related (e.g. intensity) factors that influence the ergogenic response to consuming NO3- and polyphenol-rich foods.NO3--rich food consumption increases nitric oxide synthesis, and its physiological effects are more clearly linked to increases in muscle oxygen delivery and exercise efficiency, whereas polyphenol-rich foods have less clearly established effects on nitric oxide synthesis, vascular function and physiological variables during exercise.
Nitrate
Findings and proposed mechanisms
This meta-analysis provided evidence that consumption of dietary NO3-, particularly via consumption of beetroot, provided trivial but significant benefits for endurance exercise performance. This finding corresponds with other reviews that have investigated the ergogenic potential of NO3-, despite some differences in eligible performance measures (e.g. minimum performance duration, inclusion of non-locomotor performance) and the inclusion of non-food-derived sources such as sodium and potassium NO3- [165, 166]. Within this review, NO3- consumption displayed significant, small benefits for TTE performance and trivial benefits for TT, GXT performance, with effect sizes aligned with those of McMahon et al. [165]. This review also assessed the effects of NO3- on intermittent performance tests, which are more relevant for team-sport athletes given the intermittent nature of their competition, and trivial benefits were found for ITT and IGXT performance. Consistent with Campos et al. [165], we found that effects of NO3- on exercise performance are reduced in more highly conditioned athletes. Sub-group analyses indicated that while no effects were evident for athletes with higher V̇O2max values (>65 ml.kg.min-1), there were significant small and trivial benefits from NO3- consumption in males with a V̇O2max of 45-55 and 55-65 ml.kg.min-1, respectively.
Overall, these results suggest that beetroot juice may confer the greatest benefit in males of lower fitness, particularly during TTE tests.
The improvements in exercise performance may have resulted from increases in nitric oxide synthesis and vascular function, as inferred via elevated levels of NO3-and nitrite, and reductions in systolic blood pressure (Additional Material 3), which enhance oxygen delivery and exercise efficiency [8]. These exercise effects were most apparent in less-trained individuals, who demonstrated more frequent reductions in submaximal oxygen consumption and augmentation of tissue oxygenation and oxygen uptake kinetics following NO3- supplementation (Additional Material 3). Improvements in exercise performance with NO3- intake are believed to be a result of improved mechanical efficiency and V̇O2 kinetics that derive from effects on fast-twitch muscle fibres [8], such as enhancement of excitation-contraction coupling. However, the reduced percentage of fast-twitch fibres and increased expression of calcium handling proteins [167] in elite endurance athletes, may limit these effects, in addition to their increased levels of endogenous nitric oxide synthesis [168, 169], vascular function [26, 29] and habitual dietary NO3- intake [170].
REFERENCE
Noah M. A. d'Unienville et al, 2021. "Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials", Journal of the International Society of Sports Nutrition (2021). DOI: 10.1186/s12970-021-00472-y
Medical Express (News Article) URL
https://medicalxpress.com/news/2022-06- ... y-nwletter
