Beetroot juice boosts stamina, new study shows August 6th, 2009 Image: Wikimedia Commons
(PhysOrg.com) -- Drinking beetroot juice boosts your stamina and could help you exercise for up to 16% longer. A University of Exeter led-study, published today, shows for the first time how the nitrate contained in beetroot juice leads to a reduction in oxygen uptake, making exercise less tiring. The study reveals that drinking beetroot juice reduces oxygen uptake to an extent that cannot be achieved by any other known means, including training.
The research team believes that the findings could be of great interest to endurance athletes. They could also be relevant to elderly people or those with cardiovascular, respiratory or metabolic diseases.
The research team conducted their study with eight men aged between 19 and 38. They were given 500ml per day of organic beetroot juice for six consecutive days before completing a series of tests, involving cycling on an exercise bike. On another occasion, they were given a placebo of blackcurrant cordial for six consecutive days before completing the same cycling tests.
After drinking beetroot juice the group was able to cycle for an average of 11.25 minutes, which is 92 seconds longer than when they were given the placebo. This would translate into an approximate 2% reduction in the time taken to cover a set distance. The group that had consumed the beetroot juice also had lower resting blood pressure.
The researchers are not yet sure of the exact mechanism that causes the nitrate in the beetroot juice to boost stamina. However, they suspect it could be a result of the nitrate turning into nitric oxide in the body, reducing the oxygen cost of exercise.
The research was carried out by the University of Exeter and Peninsula Medical School and published in the Journal of Applied Physiology. The research team now hopes to conduct further studies to try to understand in more detail the effects of nitrate-rich foods on exercise physiology.
Corresponding author of the study, 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 of this research. 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."
This study follows research by Barts and the London School of Medicine and the Peninsula Medical School (published in February 2008 in the American Heart Association journal Hypertension), which found that beetroot juice reduces blood pressure.
A new study from the UK suggests that beetroot juice boosts stamina and could help you exercise for 16 per cent longer because the nitrate it contains reduces oxygen uptake which make exercise less tiring. The scientists believe the finding will be of interest not only to athletes but also to elderly people and those with metabolic, respiratory or cardiovascular diseases.
The study was led by researchers from the University of Exeter and is published in the 6 August issue of the Journal of Applied Physiology.
Professor Andy Jones of the University of Exeter's School of Sport and Health Sciences and colleagues found that drinking beetroot juice reduces oxygen uptake more than can be achieved by any other known means, including training.
Jones told the media that:
"Our study is the first to show that nitrate-rich food can increase exercise endurance."
For the double-blind, placebo-controlled, crossover study they recruited 8 men aged from 19 to 38.
The men consumed 500 ml a day of beetroot juice for six consecutive days; during the last three days they underwent a series of 'step' moderate-intensity and severe-intensity exercise tests involving riding an exercise bike.
Then on a separate occasion the men went through the same process except they consumed a blackcurrant cordial placebo instead of beetroot juice.
The men also gave blood samples and were monitored throughout the trial.
The beetroot juice contained 11.2 ± 0.6 mM of nitrate while the placebo blackcurrant juice had a negligible nitrate content.
Double-blind means neither the participants nor the administrators they interacted with knew which of the two agents was being tested, the beetroot juice or the blackcurrant cordial.
The results showed that: On days 4-6 plasma [nitrite] was significantly higher in the beetroot juice phase than in the placebo phase.
Systolic blood pressure was also significantly reduced in the beetroot juice phase (other studies have shown that beetroot juice reduces blood pressure).
During moderate exercise the oxygen uptake in the beetroot juice phase went down (the researchers estimated muscle fractional O2 extraction using near infra-red spectroscopy).
The gain of increase in lung intake of oxygen (pulmonary VO2) after starting moderate exercise was 19 per cent lower when the men consumed beetroot juice than when they consumed placebo.
Also, during severe exercise, the slow component of VO2 was lower and the time to exhaustion was higher when they took beetroot juice compared to when they took placebo. Jones and colleagues concluded that:
"The reduced O2 cost of exercise following increased dietary nitrate intake has important implications for our understanding of the factors which regulate mitochondrial respiration and muscle contractile energetics in humans."
The men were able to cycle for an average of 11.25 minutes or 92 seconds longer when they took beetroot juice which translates to about 2 per cent reduction in the time taken to cover a set distance.
Jones and colleagues aren't sure how the nitrate in the beetroot juice boosts stamina, but they suspect it is because the nitrate turns into nitric oxide in the body (hence the measure for plasma nitrite), which in turn reduces the oxygen cost of exercise.
They now hope to do more tests to understand the effect of nitrate-rich foods on what happens in the body during exercise.
Jones said they were "amazed" by the effect of beetroot juice on oxygen uptake, especially as they know of no other means that can achieve this big a difference, even training.
"I am sure professional and amateur athletes will be interested in the results of this research," said Jones.
"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," he added.
"Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans." Stephen J. Bailey, Paul Winyard, Anni Vanhatalo, Jamie R. Blackwell, Fred J. DiMenna, Daryl P. Wilkerson, Joanna Tarr, Nigel Benjamin, and Andrew M. Jones Journal of Applied Physiology (August 6, 2009). DOI:10.1152/japplphysiol.00722.2009
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