[New performance series] Can beetroot juice enhance your performance?
With the Spring gradually giving way to Summer (it doesn’t look like, but Summer is only 2 weeks away), racing season is also heating up! If you have been following along, you remember that last week we briefly talked that performance in endurance events comes down to three key aspects: the ability to intake, distribute, and utilize oxygen (maximal oxygen consumption - VO2max), movement economy (the oxygen cost of exercise at a given intensity), and the lactate threshold (the intensity above which fatigue gradually starts to accumulate until we can’t or decide to not keep going). Over the next weeks we will discuss different strategies to improve each of these components and in turn, enhance performance. The previous post showed how smiling could assist in body relaxation and in turn reduce perception of effort and oxygen consumption. Now, let’s focus on something else where the mouth is also involved.
Dietary Supplementation and Improved Exercise performance
How does it work?
Beetroot juice supplementation as a performance enhancing tool grew in popularity in recent years. While the purple coloured drink is what we usually chug in the days and hours prior to a race or training session, what we are really aiming for is an increase in the levels of dietary nitrate. When consumed, nitrate (NO3-) is reduced to nitrite (NO2-) by bacteria in our saliva. Once we swallow our food, part of this nitrite is transported to other tissues in the body via circulation, where it can be further reduced to nitric oxide (NO). It is this nitric oxide that provides the performance enhancing benefits we see. Current evidence shows that NO has a positive impact on blood flow and mitochondrial function during exercise (mitochondria are the energy producing power houses of the body), among other effects, linking the increased availability of NO to better muscle function and performance.
Simple, huh? Eat more nitrate, it is eventually converted into nitric oxide, and performance improves! And increasing the consumption of dietary nitrate is quite simple, as nitrate levels are high in foods such as green leafy vegetables and root vegetables, such as beets. In fact, a study on moderately fit individuals showed that consumption of 200g of beetroot (which contains about 500mg of nitrate) improved 5k running performance by an average of 41 seconds. But if a hearty salad is not part of your routine, nitrate supplementation can also help. In fact, a single dose of dietary nitrate (via beetroot juice, for example) has been shown to substantially increase plasma nitrate and nitrite concentrations for up to 24h following ingestion.
So, remember your mom’s advice, eat your greens and other veggies, and perform better. Case closed, right? Well, not quite. There have been many details in research studies that showed the effectiveness (or lack of) of beetroot juice that are important to notice. Let’s get to them.
Beetroot, nitrate, performance…
First, take a look at the table below. You can see the fitness level of the participants, the supplementation protocol (if it was acute or if occurred over a few days, and the quantity that was ingested), the type of test and the mode it was performed, and the results.
So, what can we see? Let’s start with the testing protocols. Back in 2007, a study (Larsen et al., 2007) demonstrated that consumption of beetroot juice for 3 days before the test could improve the oxygen cost of exercise at submaximal intensities. A follow up study (Bailey et al, 2009) showed the same, meaning that you can maintain a higher intensity at a lower energy cost to your body, and thus, perform better. There is only caveat. Time to exhaustion tests, where individuals perform a task until they can’t keep going, don’t really translate to time-trial performances, where the aim is to complete a set distance as quickly as possible, as we do during our races.
But, have no fear. Further research assessed the role of nitrate supplementation via beetroot juice and found positive results (improvements in 2.6% and 2.7%) for 4km and 16.1km time trials, respectively. Similar results were reported on 10km time trial performance (+ 1.7%) in male cyclists and triathletes after a 6-day supplementation period (Cermak et al., 2012). However, if you look at the table, after this study, we come to a long list of studies that reported no benefits in time trial tests. What happened?
Well, the main difference lies in the participants’ fitness levels. Despite significant increases in plasma nitrate and nitrite concentration following supplementation, two studies (Bescos et al., 2012; Wilkerson et al., 2012) showed no improvements in performance in well-trained athletes. In addition, one of the studies (Wilkerson et al., 2012) revealed the existence of responders and non-responders, with the increases in nitrate and nitrite not being uniform between participants, with three individuals labeled as “non-responders”. Considering only the “responders”, performance in the 50-mile time trial would have consistently improved by 2%. Still, further studies corroborated the hypothesis that highly trained individuals don’t benefit as much from supplementation (Bescos et al., 2011; Cermak et al., 2012; Christensen et al., 2013; Hoon et al., 2014; Peacock et al., 2012).
However, there is more to it. In addition to the higher fitness level of the participants, some of the tests were of longer duration and lower intensities, conditions that might not present the optimal environment for dietary nitrate to improve performance. You see, what I haven’t mentioned yet is that the pathway that turns the ingested nitrate into nitrite and then nitric oxide actually works better under conditions of low pH during exercise, which occurs with shorter duration, higher intensity exercises, but likely won’t happen with longer events. Still, the results of studies performed with highly trained athletes and short duration tests also present mixed results. One study (Christensen et al., 2013) had athletes performing repeated sprints (6 x 20s) after 6 days of beetroot ingestion, with no improvements reported, while another study (Hoon et al., 2014) had unclear results in a group of elite-level cyclists during a 4-min time trial. Contrary to these findings, using a similar 6-day supplementation protocol, rowing performance was improved in a test that included 6 sets of 500m of rowing, with improved maximal rowing ergometer performance across all repetitions (0.4%), particularly in the later stages of exercise (repetitions 4 – 6), with a 1.7% improvement in such sets.
Still, the results are inconsistent. So, where is the issue? Well, an inadequate amount of prescribed nitrate is a commonly cited reason in these studies. Indeed, a previous study (Wylie et al, 2013) performed on healthy males had demonstrated a dose-response relationship to nitrate supplementation, with nitrate and nitrite concentrations increasing in a dose-dependent manner in the three dosing protocols utilized, with the highest concentration demonstrated to be necessary to reduce the oxygen cost of moderate intensity exercise. As these results were demonstrated in healthy male adults, researchers were quick to point that perhaps highly trained athletes would need a greater acute concentration and / or longer supplementation period.
So, do they?
Well, the following studies (Hoon et al., 2014; Peeling, Cox, Bullock and Burke; 2015) showed that greater doses ingested for a longer period of time are more efficient in improving performance in highly trained athletes. Still, other studies with similar dosing protocols showed no significant improvements (Bescos et al., 2012; McQuillan et al., 2017; Peacock et al., 2012), Authors in these studies pointed out that the different intensities and durations of the testing protocols, and the mode of exercise (cycling, rowing, kayaking) are also to blame and highlighted that there must be an interaction between diverse factors that can prompt performance increases following nitrate supplementation.
By now, you are probably thinking that this is too complicated. After all, should we consume beetroot juice or not?
In short, the answer is yes (I could have saved you some reading time, right?). In a recent position statement on supplements, the International Olympic Committee highlighted dietary nitrate as only one of five supplements with good to strong evidence to improve performance (spoiler alert: the other ones are caffeine, creatine, sodium bicarbonate, and beta alanine – we’ll talk about them at a later time). In addition, a new study (Rokkedal-Lausch et al., 2019) showed that with the proper supplementation protocol and the right testing distance (10km in this case) even highly trained (and these were really highly trained athletes) can see benefits from it. We just have to temper our expectations depending on fitness level, dosing protocol, our mode of exercise, and the duration of it.
If you are a recreational athlete, your chances of seeing your performance improve are much greater. You can consume it acutely (approximately 2 - 3 hours before the event, to allow enough time for the nitrate to be processed in the body), in a manner that allows for a total consumption of 310 to 560mg of nitrate. No idea where that can come from? Well, that initial study that mentioned 200g of beets is a nice start. But honestly, beetroot juice might be your easier bet (you can even check the nitrate content in the label). You can also gradually increase your intake in the days prior to the event (most chronic protocols are usually 3 to 7 days) and can either consume more foods that are rich in nitrate (leafy green and root vegetables, including spinach, rocket salad, celery, and beetroot) or supplement with beetroot juice. Your performance will also be better if the event is of shorter duration (< 40min); and if the mode of exercise relies more heavily on fast (type II) muscle fibers – these are usually utilized in shorter duration, more intense events, and exercises that have a greater participation of the upper body, such as rowing and kayaking (which explains some of the results discussed above). And even though the end product is nitric oxide, know that direct ingestion of NO (it can be easily seen for sale in your nearest supplement store) is not effective.
So, considering all the available evidence, it appears that nitrate supplementation has the potential to increase endurance performance, being a great ergogenic aid particularly for recreational athletes. It will reduce your oxygen cost of exercise (improving your movement economy), and possibly reduces your perception of effort (at least early in your race). Just make sure that you don’t try anything new on race day. If you are looking for a performance booster, give it a try during a few training sessions beforehand. It is always better to get your stomach used to anything new before a race. The last thing you need prior to your race is showing off how great you are going to perform with a sprint to the nearest toilet.
Interested in knowing more about it? Check any of the papers below:
Bailey, S. J., Fulford, J., Vanhatalo, A., Wyniard, P. G., Blackwell, J. R., DiMenna, F. J., … & Jones, A. M. (2010). Dietary nitrate supplementation enhances muscle contractile efficiency during knee extensor exercise in humans. Journal of Applied Physiology, 109 (1): 135 – 148. http://dx.doi.org/10.1152/japplphysiol.00046.2010
Bescos, R., Rodriguez, F. A., Iglesias, X., Ferrer, M. D., Iborra, E., & Pons, A. (2011). Acute administration of inorganic nitrate reduces VO2peak in endurance athletes. Medicine and Science in Sports and Exercise, 43 (10): 1979 – 1986.
Bescos, R., Ferrer-Roca, V., Galilea, P. A., Roig, A., Drobnic, F., Sureda, A., … & Pons, A. (2012). Sodium nitrate supplementation does not enhance performance of endurance athletes. Medicine and Science in Sports and Exercise, 44 (12): 2400 – 2409. http://dx.doi.org/10.1249/MSS.0b013e3182687e5c
Bond, H., Morton, L., & Braakhuis, A. J. (2012). Dietary nitrate supplementation improves rowing performance in well-trained rowers. International Journal of Sports Nutrition and Exercise Metabolism, 22 (4): 251 – 256.
Cermak, N. M., Gibala, M. J., & van Loon, L. J. C. (2012). Nitrate supplementation’s improvement of 10-km time-trial performance in trained cyclists. International Journal of Sport Nutrition and Exercise Metabolism, 22 (1): 64 – 71.
Cermak, N. M., Res, P., Stinkens, R., Lundberg, J. O., Gibala, M. J., & van Loon, L. J. C. (2012). No improvement in endurance performance after a single dose of beetroot juice. International Journal of Sport Nutrition and Exercise Metabolism, 22 (6): 470 – 478.
Christensen, P. M., Nyberg, M., & Bangsbo, J. (2013). Influence of nitrate supplementation on VO2 kinetics and endurance of elite cyclists. Scandinavian Journal of Medicine & Science in Sports, 23 (1): e 21 – e31. http://dx.doi.org/ doi: 10.1111/sms.12005
Hoon, M. W., Hopkins, W. G., Jones, A. M., Martin, D. T. Halson, S. L., West, N. P., … & Burke, L. M. (2014). Nitrate supplementation and high-intensity performance in competitive cyclists. Applied Physiology, Nutrition, and Metabolism, 39 (9): 1043 – 1049. http://dx.doi.org/10.1139/apnm-2013-0574
Hoon, M. W., Jones, A. M., Johnson, N. A., Blackwell, J. R., Broad, E. M., Lundy, B., … & Burke, L. M. (2014). The effect of variable doses of inorganic-rich beetroot juice on simulated 2000m rowing performance in trained athletes. International Journal of Sports Physiology and Performance, 9: 615 – 620. http://doi.org/10.1123/ijspp.2013-0207
McQuillan, J. A., Dulson. D. K., Laursen, P. B., Kilding, A. E. (2017). Dietary nitrate fails to improve 1 and 4km cycling performance in highly trained cyclists. International Journal of Sports Nutrition and Exercise Metabolism, 27 (3): 255 – 263.
Peacock, O., Tjonna, A. E., James, P., Wisloff, U., Welde, B., Bohlke, N., … & Sandbakk, O. (2012). Dietary nitrate does not enhance running performance in elite cross-country skiers. Medicine and Science in Sports and Exercise, 44 (11): 2213 – 2219. http://dx.doi.org/10.1249/MSS.0b013e3182640f48
Peeling, P., Cox, G. R., Bullock, N., & Burke, L. M. (2015). Beetroot juice improves on-water 500m time trial performances, and laboratory-based paddling economy in national and international level kayak athletes. International Journal of Sports Nutrition and Exercise Metabolism, 25: 278 – 284.
Sandbakk, S. B., Sandbakk, O., Peacock, O., James, P., Welde, B., …, & Tjonna, A. E. (2015). Effects of acute supplementation of L-arginine and nitrate on endurance and sprint performance in elite athletes. Nitric Oxide, 48 (8): 10 – 15. http://dx.doi.org/10.1016/j.niox.2014.10.006
Wilkerson, D. P., Hayward, G. M., Bailey, S. J., Vanhatalo, A., Blackwell, J. R., & Jones, A. M. (2012). Influence of acute dietary nitrate supplementation on 50-mile time trial performance in well-trained cyclists. European Journal of Applied Physiology, 112 (12): 4127 – 4134. http://dx.doi.org/10.1007/s00421-012-2397-6