A research team at the University of Exeter has just published results of a study which shows (1) that drinking beetroot juice may help boost stamina and help individuals to exercise for up to 16% longer than they are normally able to, this may be down to the nitrate content of the beetroot juice.  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, which can relax blood vessels and increase blood flow.

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.

This was a very small, preliminary study which took place in men (1).  The participants were given 500ml of organic beetroot juice each day for 6 days before completing a series of tests involving cycling on an exercise bike – the exercise tests ranged from moderate-intensity to severe-intensity.  On a separate occasion the same men were given a blackcurrant cordial drink for six consecutive days before completing the same cycling tests.  After drinking beetroot juice the group was able to cycle for significantly longer than when they were given the placebo blackcurrant drink.  The men also gave blood samples throughout the trial.

The beetroot juice contained around 11.2 mM of nitrate while the placebo blackcurrant juice had a negligible nitrate content.  The study was performed ‘double blind’ which means that 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.

On days 4-6 the blood plasma nitrite levels were significantly higher in the beetroot juice phase than in the placebo phase and the blood pressure of participants was also significantly reduced in the beetroot juice phase (other studies have shown that beetroot juice can reduce blood pressure).  The authors are not 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.  The research team now hopes to conduct further studies to try to understand in more detail the effects of different nitrate-rich foods on exercise physiology.  Nitric oxide in the body helps to relax blood vessels and increase blood flow, hence can be important for reducing blood pressure, in the body.

One of the study authors said in a press release (2): "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." 

Arginine supplements are available to buy and have been shown to be useful to increase nitric oxide levels in the body.  The amino acid, Arginine, is a powerful vasodilator (blood vessel relaxer) and may help to support and maintain healthy blood flow and circulation. Arginine is also an antioxidant and helps support healthy arteries.  Beetroot drinks and supplements are also available to by but it is important to remember that supplements should not be viewed as a substitute for a healthy balanced diet and lifestyle.  Beetroot is also rich source of vitamins, minerals, antioxidant bioflavonoids (bioactive plant compounds) and fibre and would certainly be a good vegetable to include as part of a varied and balanced diet.

(1)Wilkerson DP et al.  2009.  Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans.  Journal of Applied Physiology (August 6, 2009).  DOI:10.1152/japplphysiol.00722.2009
(2) University of Exeter Press release.  Beetroot juice boosts stamina, new study shows http://www.exeter.ac.uk/news/featurednews/title,37371,en.php

Written by Ani Kowal