Scientists found that athletes who drank the juice before exercise could increase their stamina by up to 20 per cent.
The discovery could revolutionise endurance sports and boost the chances of Britain’s 2012 Olympic hopefuls.
It could also be important for the elderly and people with heart or lung disease.
Researchers at the University of Exeter asked eight men aged between 19 and 38 to drink half a litre of organic beetroot juice every day for six days, before completing a series of exercise bike tests. On another occasion they were asked to carry out the same tests, having swapped the juice for blackcurrant cordial.
After they were given beetroot juice, the men were able to cycle flat-out for an average of 11.25 minutes – 92 seconds longer than when they drank the blackcurrant. This translated to a reduction in the time taken to cover a set distance of about two per cent. Drinking beetroot juice also led to a lower resting blood pressure.
It is thought that high levels of nitrate in the juice turn into nitric oxide in the body. This means less oxygen is needed to keep the muscles going, therefore boosting endurance.
Professor Andy Jones, of the University of Exeter’s School of Sport and Health Sciences, said: “Our study is the first to show that nitrate-rich food can increase exercise endurance. We were amazed by the effects of beetroot juice on oxygen uptake because these effects cannot be achieved by any other known means, including training.
“I am sure professional and amateur athletes will be interested in the results.
“I am also keen to explore the relevance of the findings to those people who suffer from poor fitness and may be able to use dietary supplements to help them go about their daily lives.”
The study is published in the Journal of Applied Physiology.
Nitrate can be found in other foods, particularly leafy vegetables, but beetroot can be juiced, which is the best way to ingest large amounts.