The effects of multi-day vs. single pre-exercise nitrate supplement dosing on simulated cycling time-trial performance and skeletal muscle oxygenation
Link to research paper
What is the deal with nitrates?
You have probably heard from someone or from somewhere the benefits of beets or beetroot powder supplements. Nowadays, more and more athletes are picking up on the benefits of beets/beetroot powder. Why? Well, beets contain nitrates, and these nitrates are receiving a lot of attention in the research literature. There are actually very, very few supplements/substances that have any real research backing them up (disappointing, I know). Caffeine and creatine are two of the most well studied and evidence-backed supplements out there with REAL performance benefits. Nitrate supplementation, however, has quite a bit of research to back it up, with study after study showing that nitrates have a beneficial effect on endurance performance. Previous research has found that supplementing one's diet with nitrates (often from beet/beetroot powder supplements) has a beneficial effect on endurance performance. Nitrates, when consumed from food or supplements, are converted to nitrites in the body, and further converted to nitric oxide (NO) when the body is placed under metabolic stress (exercise is one way to place the body under metabolic stress). Why is NO important you may ask? Well, NO acts as a vasodilator (opens up and expands blood vessels) and helps to regulate blood flow throughout the body. Higher levels of NO in the body have been shown to improve the efficiency of aerobic metabolism (very, very important metabolic process for endurance athletes) as well as improve overall exercise economy (essentially the efficiency of your movement). These are some pretty big potential benefits, and research has shown that supplementation of one's diet with nitrates improves time trial performance in endurance activities (most studies focus on cycling or running time trial performance). However, how long does one need to supplement with nitrates to get a performance benefit? Does one get an immediate performance benefit from taking a nitrate supplement? Or does one need to consume a nitrate supplement over a prolonged period of time to reap the rewards? These are questions that this recent study investigated.
What did the researchers study?
The primary purpose of this study was to investigate the effects of long-term vs. single dosing nitrate supplementation on cycling time trial performance. To answer this question, researchers randomly assigned healthy, recreationally active men and women to either a long-term nitrate supplementation group (14 days of supplementation) or a single dosing nitrate supplementation group (1 day of supplementation). A total of 14 participants were assigned to the long-term supplementation group and 15 assigned to the single dosing group. Participants in both groups performed a pre-intervention 5-mile cycling time trial immediately upon enrollment into the study and then proceeded to take either 14 days of nitrate supplementation in the long-term supplementation group (500 mg nitrate per daily dose) or 14 days of a placebo pill in the single dosing group (no nitrate). Both groups then took a nitrate supplement 2 hours before the post-intervention cycling time trial performance.
What are the major findings?
Interestingly, the 14-day nitrate supplementation improved cycling time trial performance (less time to complete, improved average power output and speed), whereas the single dosing group did not see any performance benefit. Performance improved by ~4-5% in those taking the nitrate supplement for 14 days.
What do these findings mean to YOU as an endurance athlete or coach?
There is an increasingly larger and larger body of evidence to support the potential benefits of nitrate supplementation for endurance athletes, and this study helped demonstrate that long-term nitrate supplementation may be most effective in improving time trial performance. Why? Well, nitrate consumption needs to be done on a daily, long-term basis in order to increase nitrite stores in the body. A single dose of nitrates before exercise will not be enough to increase nitrite stores over time. It is the increase in nitrite stores that allows your body to produce more NO during exercise, which I mentioned before improves the efficiency of the body's aerobic metabolic pathway and improves overall exercise economy. These benefits may be of importance to athletes participating in endurance events. The majority of research has looked at short duration endurance events such as 5-10K cycling time trials and running time trials. Research has yet to suggest if the benefits extend to athletes participating in very prolonged events such as marathons and Ironman-distance races. My take on this research is this: If you participate in endurance events (regardless of the distance) and are serious about improving your performance with the little 1-2% difference maker, it may be worth trying out nitrate supplementation or aiming to consume foods high in nitrates as there seems to be some evidence to support its benefits for endurance performance. At the very least, there are other health benefits of nitrates even if you don't get a performance boost and, if don't like it or don't feel like it helps you, then you can simply stop taking it!
Now, you are probably wondering what the heck you can buy or eat/drink that has nitrates in it? Well, first of all, you want to make sure you consume ~500 mg of nitrates on a daily basis over time because research tends to show this is an effective dose for performance enhancement. Anything drastically less than this and taken inconsistently over time may not yield any performance benefit. To get 500 mg of nitrates, you could drink ~2 cups of beet juice, eat 3-4 cup of raw spinach (dark, leafy greens also have a high nitrate content), or take a beetroot supplement.
Now, I'm not a Registered Dietician and usually not a fan of taking supplements as most supplements are not really going to be doing much for you other than sucking money out of your wallet, and most beetroot supplements will be doing just this. Most beetroot extract supplements contain far too little beetroot extract to contain a sufficient quantity of nitrates. Buying beetroot supplements is tricky as it can be hard to find the dosage of beetroot listed on the label, and when you do find it, you might have to do a bit of converting to figure out how much nitrate is actually in the supplement, because after all, you really care about the nitrate content and not the beetroot. Most supplements out there contain 500-2000 mg of beetroot extract, and unfortunately this is nowhere near 500 mg (or 5-9 mmol) of nitrates that research demonstrates is effective. So, food might be the better option for obtaining nitrates. Remember, just 3-4 cups of spinach could get you close to that target 500 mg of nitrates, so it's not just beets.
I do have to say that the science of nitrate supplementation is ever-evolving, and there is research to suggest that effective doses of nitrates ranges a bit. If you want to read a bit more into the effects of nitrate supplementation (there are other benefits outside of improved time trial performance), the link below will take you to an evidence-based educational organization's website that independently examines nutrition and supplement research. They are a great resource for anyone wanting to learn more about evidence-based supplements, and sure enough, they did an independent investigation into the effects of nitrate supplementation. This page may provide you with even more information than I have provided here as they looked at and summarized a lot of literature surrounding nitrate supplementation: https://examine.com/supplements/nitrate/.
I hope you enjoyed this piece! If you have any comments or questions, drop them in the comments section below and let's get a discussion started.
Happy training and racing!
-Ryan Eckert, MS, CSCS
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