In the endurance sport world, we’re always looking for easy ways to improve our performance. Consequently, there are an ever-growing number of supplements claiming to help us go faster without having to train any harder. Of course, nothing beats committed training, but do any of these supplements actually produce the ‘marginal gains’ that they say they do?
One product which has gained interest over the last few years is beetroot juice. In fact, during the road cycling world championships in 2012, the local supermarket in the small race town sold out of the drink, such was its popularity among the cyclists. This is interesting, because rather than a chemical concoction manufactured by scientists, beetroot is a common food which we are all familiar with.
The attraction of beetroot juice comes from its high nitrate concentration. Nitrates are a chemical compound which are not that useful to performance on their own, but once ingested, are converted to one of the key signalling molecules in the body, Nitric Oxide (NO). Among its numerous actions, NO allows the blood vessels to dilate and constrict, thereby controlling the rate of blood flow through the body. Because oxygen is carried in the blood, this also affects how quickly oxygen can be delivered from the lungs to the muscles, and how many of the smaller blood vessels surrounding the muscles are filled with blood. NO may also improve the efficiency of mitochondria (the cell components which use oxygen to make energy), so that less oxygen is required to produce a certain amount of energy and perform exercise of a particular intensity.
From a scientific point of view, the ability of beetroot juice to improve performance seems plausible, but does this work in real life. Firstly, we’ll look at the typical ‘weekend warrior’ type athletes. In these individuals, the evidence that beetroot juice has an impact is pretty strong. Numerous studies, primarily conducted at the University of Exeter, have shown a reduction in the amount of oxygen needed to bike at a particular power output (of submaximal intensity) when beetroot juice was consumed either in one large dose several hours before the exercise, or for several days prior. Importantly, this improved performance in a following higher intensity time trial or ‘time to exhaustion’ protocol. This suggests that the lower oxygen requirement of the initial exercise allowed better performance in the subsequent performance test.
However, as with a number of dietary interventions, beetroot juice does not tend to have much of an effect when given to elite or highly-trained athletes. While these athletes still show an increase in blood markers of NO production, they rarely have any changes in their oxygen consumption or exercise performance, even when very large quantities of beetroot juice are ingested. This is probably due to the increased blood vessels, mitochondria, and internal NO production that these athletes already have as a result of their large training volumes. This means they already have a greater capacity to transport oxygen than an average athlete, so the extra Nitric Oxide does not produce as much (or any) effect.
So is beetroot juice worth taking? If you’re a highly-trained athlete, probably not. But if you’re a weekend warrior looking for a boost in your next endurance event, it’s worth a try. The key points to remember if you’re going to try beetroot juice are:
• Look for a juice which is as close to 100% beetroot as you can find. Alternatively, there are various beetroot ‘shots’ on the market, which provide a more concentrated source of nitrates. Scientific research has shown improvements in exercise performance with 0.5L of pure beetroot juice (equivalent to about 5.5mmol nitrate).
• Drink the juice about 2.5 hours before your event. The peak blood concentration of nitrates following beetroot juice consumption occurs between 2-3 hours.
• Avoid mouthwash and chewing gum when taking beetroot juice. These products kill bacteria on the tongue which are necessary for the conversion of nitrate to nitric oxide.
• Test it out before race day. While most studies have not reported any side effects from drinking large quantities of beetroot juice (apart from ‘beeturia’ or purple urine!), it’s always best to make sure a supplement is not going to cause you gastrointestinal distress.
Emma Crum
Sport Scientist
Performance Advantage
e.crum@massey.ac.nz
