Tuesday, February 5, 2013

With Beetroot Juice to the SuperBowl XLVIII: 490ml Beetroot Juice Will do the Ergogenic Trick in Team Sports. Plus: Brief Research Overview to Identify Who Else Will Benefit

There are a couple of important confounding factors which will determine whether or not you or anyone else can benefit from nitrate supplementation. Sex is yet - as far as I know know - not one of them... ah, by the way, there may be other benefits to nitrates that are "sex-specific", but in this case the semantics are somewhat different ;-)
You know that the SuppVersity is all about self-education (hence "-versity" as in University), so what would be better than using the publication of the latest paper on the purported ergogonic effects of nitrates as an incentive to "inform" you about the current state of the research? Sounds good? I would think so. Let's take a look, then. What's this nitrate business all about? Contrary to the argument many supplement vendors have been bringing forward to make muscleheads buy their products, the idea is not to use the vasodilating effects for cosmetic pumps that will make you feel - as Arnold said it - better than you felt last night with your significant other (or whom ever else you may have picked up). It's rather their purported effect on the VO2max, which is the maximal oxygen consumption during a workout and the downstream performance effects that puts scientists on -- scientists like Lee J. Wylie and colleagues from the department of Sport and Health Sciences at the University of Exeter, for example (Wylie. 2013).

The latest on dietary nitrate supplementation: Focus on team sport athletes

The paper we are taking a closer look at today has just been published ahead of print in the European Journal of Applied Physiology and investigated the acute effects 490 mL of concentrated, nitrate-rich beetroot juice (BR) and nitrate-depleted placebo juice (PL) had on the performance of fourteen male recreational team-sport players during a Yo–Yo intermittent recovery level 1 test (Yo–Yo IR1) that was performed ~30h after the ingestion of the purported ergogenic (the Yo-Yo IR1 test has been found to mirror the physical demands encountered during team sports, like soccer, football, basketball, rugby etc petty accurately.; cf. Atkins. 2006; Veale. 2010; Vernillo. 2012).
Would dosages as high as in the study at hand (or even higher) provide similar muscle gains, as they were observed with "real" nitrate in rodents (read more).
A note on the "optimal" dosage: The dosage that was used in the study at hand is equal to  ~29 mmol of nitrate, which is 4x more than the current recommended daily allowance in the UK and 6x more than what was most in the majority of previous. Aside from the subjects' training status, which has emerged as a possible confounding factor determining whether athletes will benefit from the consumption of beet-root juice / dietary nitrates, the dosage, as well as the plasma nitrate response (+400% vs. 50-150% in other trials), which was likewise much higher in the Wiley study than in most previous studies, could thus be another important, if not the most important confounding factor. Whether the "more helps more principle" actually holds, whether athletes need more than normalos and if / at which dosages negative side effects occur will yet still have to be elucidated in future trials.
As it was to be expected, the resting plasma nitrite concentration NO2(-) was ~400 % greater in the active compared to the passive trial of this double-blind, randomized cross-over trial (remember: Cross-over means, all participants completed two tests sessions on seperate occasions, one w/ the active, one with the placebo supplement).
Figure 1: Effects of 490ml beetroot juice on serum NO2/3(-) levels, performance and mean glucose concentration during the Yo-Yo R1 test (Wylie. 2013)
As you will learn from the comprehensive research overview further down, the fact that this increase in plasma NO2(-) did also translate into performance increases, on the other hand, was not really to be expected:
Betaine (TMG) increses IGF-1 & lowers cortisol (read more)
"Plasma [NO2 -] declined by 20 % in PL (P\0.05) and by 54 % in BR (P<0.05) from pre-exercise to end-exercise. Performance in the Yo–Yo IR1 was 4.2 % greater (P<0.05) with BR (1,704±304 m) compared to PL (1,636 ±288 m). Blood [lactate] was not different between BR and PL, but the mean blood [glucose] was lower (3.8 ±0.8 vs. 4.2±1.1 mM,P\0.05) and the rise in plasma [K+] tended to be reduced in BR compared to PL (P=0.08)." (Wylie. 2013)
That being said the study at hand confirms that the consumption of a significant bolus of nitrate with all the natural co-factors in beetroot, i.e. >20 betacyanins + derivatives, 11 betaxanthins, highly bioavailable folate, various carotenoids, and, of course betaine has beneficial ergogenic effects on the performance of recreationally active men (Nemzer. 2011). As we are about to see both, the training status of the subjects, as well as the nutrient combination (or absence of the latter) may be a confounding factor due to which this trial was a success whereas ostensibly similar ones were failures.

How does that stuff actually work?

Before we go over to the comparison phase, let's yet briefly check out what the scientists have to say about the underlying mechanism(s) of the ergogenic effects they observed:
  • reduction of NO3(-) to NO2(-) and in (sub-)hypoxic or acidic conditions to NO (nitric oxide) - Based on their data, the researchers speculate that this it is likely that this reduction took place during the Yo-Yo  IR1 test (it''s about as likely in most similar high intensity exercise protocols). Base on previous data from Dreissigacker et al. who found signficantly higher baseline NO3(-) and NO2(-) levels in trained vs. untrained subjects an the results of Totzeck et al., who found that baseline NO2(-) correlates with lactate threshold and predicts exercise capacity during an incremental cycle test in highly trained athletes, Wiley and his colleagues argue that it is more than likely that the ability to produce more NO quasi 'on demand' is the underlying cause of the performance increases (Dreissigacker. 2010, Totzeck. 2012).
  • dietary nitrate supplementation can protect the phosphocreatine (PCr) stores from being depleted - With PCr being the most readily available energy source for short burst activities like sprinting the preservation of the PCr stores (similar to their "supercharging" via supplemental creatine; click here to learn all about creatine supplementation) would certainly explain why the nitrate supplement delay, what the scientists label as "the attainment of a ‘critical’ intramuscular environment"  and would thus "extend the tolerable duration of high-intensity constant-work-rate exercise". This hyptothesis woul be supporte by the fact that NO increases skeletal muscle glucose uptake, the correspondingly lower blood glucose levels the researchers observed in the active arm of the study and the fact that readily available glucose will spare the PCr stores.
  • decreased leakage of K+ (potassium) from the muscle - As the post hoc analysis revealed significantly lover plasma K+ levels during the beetroot juice condition of this double-blind ranomized cross-over study after 600 m of the test, a third mechanism by which the supplementation protocol could have postponed fatigue would thus be the preservation of the electrical potential which is established by the distribution of K and Na ions inside, respectively outside of the muscle cell.
  • increased oxidative capacity and consequent glucose sparing - Previous rodent studies have shown that nitrate supplementation increases blood flow and oxygenation of the muscle, the latter could translate into faster recovery of the glycogen content of the muscles in the short recovery phase.
  • increased force production due to increased sarcoplasmic reticulum calcium release and force production - The increase in force would likewise have an energy sparing effect as it would mean that at a given exercise intensity (in watts) a lower number of muscle fibers would have to be recruited to get the job done. As with the previous information on the oxygenation of the muscle, this is yet based on observations in rodents and warrants verification in human studies.

Irrespective of the underlying mechanisms, it's likewise necessary to put them into perspective before we freak out and start raving about a new "superstar supplement" being born. After all, the effect size was significant, but comparably modest. A 2011 study by Mohr et al. for example observed a +16% performance increase after the ingestion of 6mg/kg caffeine in a subsequent Yo–Yo IR2 test (Mohr. 2011) and the effect simple training (i.e. +29% for sprint-endurance training; cf. Mohr. 2007) has on the perfomance in the same test, is likewise nothing to sneeze at.

So what did previous studies show?

As I have already hinted at in the red infobox a couple of paragraphs above, the dosage alone may explain why Wiley et al. did observe beneficial effects of nitrate / beetroot juice supplementation, while previous studies have shown very mixed results. Two other factors, I have highlighted in the following mini-overview (in bold and w/ an underline) that are probably relevant, are the training status of the study participants and the duration of the supplementation:
The combination of beta-alanine an baking soda (esp. the latter) may serve as a viable alternative for those trainees who are "too advanced" for nitrates to do the trick (read more)
You should by now be aware that orally ingested arginine does not induce significant NO boosts or performance increases, but did you know that it could help you get shredded? (read more)
  • recreationally active and trained but sub-elite subjects, short-term dietary nitrate supplementation: 
    • increased exercise tolerance at a fixed sub-maximal work rate (Bailey. 2009, 2010; Lansley. 2011b)
    • increased power output during self-paced endurance exercise leading to improved cycle time-trial performance (Cermak.2012a; Lansley. 2011a).
  • well-trained subjects (details in brackets) short-term dietary nitrate supplementation:
    • higher mean power output in HIIT 6 x 500m rowing trial (rowers, Bond. 2012)
    • little / no effect in endurance trained athletes in their respective disciplines (Besco. 2012; Cermak. 2012b; Christensen. 2013; Peacock. 2012; Wilkerson. 2012) 
  •  recreationally active no regular, planned exercise, regimen chronic nitrate supplementation:
    • reduced BP and the O2 cost of submaximal exercise are maintained over 15d supplementation period (Vanhatalo. 2010)
The number of studies investigating the long-term effects of nitrate supplementation is to low to make a definite statement about whether or not it may be likely that short-term supplementation studies, in the course of which the researchers did not observe any ergogenic benefits of supplemental nitrate, would have yielded different results, if the supplementation had lasted for a couple of days or weeks.

Did you know that the scientists adjusted the comparatively high dosage of dietary nitrate the subjects received in the study at hand to the levels you would get, if you followed the anti-hypertensive DASH (Dietary Approaches to Stop Hypertension) diet? Obviously not an there is a good reason I am telling you that, 'cause this means that a paleo-ish high greens diet could in fact bring your nitrate levels into the same range as those of the subjects in the active trial of the study at hand - without having to spend a single buck on extra supplements, of course.
Nevertheless, the results Vanhatalo et al. present, namely that the effects persist in recreationally active subjects over 15 days of continuous supplementation, do actually stand in line with the hypothesis that the low / non-existent response in highly trained athletes could be due to their higher baseline NO3(-) and NO2(-) levels. I have invoked the latter in the discussion of the possible beneficial effects of NO generation in the previous discussion of the underlying mechanisms, already. If we assume that there is some sort of a saturation level and/or at least a logarithmic response to nitrate supplementation, where high baseline levels require even higher amounts of supplemental NO3(-) in order to bump the levels further up, we would have to conclude that
  • highly trained athletes won't benefit from nitrate supplementation at all, because their blood NO3(-) levels are "saturated" and don't respond to supplementation
  • highly trained athletes need way more nitrate to see a minimal increase in their NO3(-) levels
If the former was the case, nitrate supplementation would not make sense at all for highly trained athletes, if the latter was the case, it could produce benefits, but those would be much less pronounced than those observed in the study at hand or similar studies with recreationally active or even previously sedentary individuals.

Bottom line: I seriously can't tell you whether you will see significant performance increases from dietary nitrate supplementation. Unfortunately, especially those of you for whom even small increases in performance count, namely people with years of training under their belt, are probably the ones who benefit least. That being said, nitrates are probably not going to make it into the SuppVersity "must have" supplement list (read more about those in Part II of my recent interview w/ Sean Casey). The fact that they can have ergogenic effects, especially for HIIT and other "endurance-like" exercises with non-aerobic elements in themm is yet obviously indisputable. Whether they are worth the money effective dosages would cost you is yet highly questionable.... When I think about all the rest of purported ergogenics you can buy all over the Internet, a nitrate supplement or a 6-pack of beetroot juice are yet probably still better investments than 90% of the other "auxiliary" revenue,... ah pardon me, I mean "performance enhancers" the supplement market has to offer  ;-)

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