A performance-enhancing product is available in every health-food shop: ordinary beetroot juice. Drink half a litre of the stuff two hours before cycling or running and, according to a human study from the University of Exeter, you'll improve your time by nearly three percent.
The ergogenic effect of beetroot juice has nothing to do with a special vitamin analogue, or an obscure flavonoid or alkaloid. It's due to a substance that ten to twenty years ago nutritionists warned not to eat too much of: nitrate. Today, however, it seems that the risks of nitrate found in food are not so high after all, and some research has even shown that nitrates have health benefits. After all, they are precursors of a substance you're probably familiar with – nitrogen monoxide or NO for short.
NO is a 'good' free radical. For strength athletes NO is a substance that tells young muscle cells they have to grow into mature muscle cells; for endurance athletes NO is a substance that widens blood vessels and therefore increases the supply of oxygen to muscle cells. And endurance athletes that keep up with science news may also know of a study done by the same Brits, which showed that NO helps muscles cells to use oxygen more sparingly during intensive endurance exercise. [J Appl Physiol. 2009 Oct; 107(4): 1144-55.] This is because NO induces muscle cells to get more energy out their creatine and ATP, and delays the moment at which muscle cells start to burn carbohydrates.
[And while we're on the subject, it occurs to us: if a bodybuilder were to drink beetroot juice before doing supersets – would that boost his EPOC?]
In the study that was recently published in Medicine & Science in Sports & Exercise, the researchers gave nine well-trained cyclists half a litre of beetroot juice and got them to do a four-kilometre timed ride two hours later. The researchers then repeated the procedure, but gave the cyclists nitrate-free beetroot juice [PL]. The figures below show that beetroot juice [BR] reduced the cyclists' time for the 4-km ride by 2.8 percent and increased their power output and the ratio of the power output to oxygen expenditure.
The researchers also obtained similar results when they got the cyclists to do a 16-km timed ride.
"It should be recognized that the relationship between dietary nitrate intake and human health is controversial", the researchers conclude in their study. "Although increased consumption of nitrate-rich natural vegetable products is unlikely to be harmful to health, presently little is known about the effects of chronic ingestion of nitrate at high doses."
Med Sci Sports Exerc. 2011 Jun;43(6):1125-31.