The purple root vegetable contains high levels of chemicals called nitrates, which have been shown to boost exercise performance.

Researchers at St. Louis University in America found athletes were able to run five kilometers faster after eating beetroot than after eating cranberries.

It follows other studies that have shown beetroot juice can increase stamina and make muscles more efficient.

The St. Louis team recruited 11 fit and healthy men and women and asked them to run five kilometers on a treadmill, twice.

Before the first run, the volunteers consumed a portion of baked beetroot, of about 200g, or 7oz., of beetroot just over an hour before hitting the treadmill.

Before the second run, they ate an equivalent amount of cranberry relish, chosen because it has a similar calorific content to beetroot but without the same nitrate levels.

The results, published in the Journal of the Academy of Nutrition and Dietetics, showed that after eating the cranberry relish, the runners averaged a speed of 11.9 kilometers per hour.

However, after consuming beetroot, their average speed went up to 12.3 kilometers per hour.

Researchers said runners appear to be able to speed up in the last section of the run after eating beetroot.

In a report on their findings, they said, "During the last 1.1 miles of the run, speed was 5% faster in the beetroot trial."

Lead author Margaret Murphy wrote in the journal, "Consumption of nitrate-rich, whole beetroot improves running performance in healthy adults.

"Because whole vegetables have been shown to have health benefits, whereas nitrates from other sources may have detrimental health effects, it would be prudent for individuals seeking performance benefits to obtain nitrates from whole vegetables, such as beetroot."

It follows previous research on the benefits of beetroot juice carried by out Peninsula Medical School in Exeter.

One published in the Journal of Applied Physiology in 2010, found that after drinking the juice participants muscles were more efficient and used less oxygen while walking.

Katie Lansley, a PhD student from the university’s Sport and Health Sciences department and lead author of the study, said, “As you get older, or if you have conditions which affect your cardiovascular system, the amount of oxygen you can take in to use during exercise drops considerably. This means that, for some people, even simple tasks like walking may not be manageable.

“What we’ve seen in this study is that beetroot juice can actually reduce the amount of oxygen you need to perform even low-intensity exercise. In principle, this effect could help people do things they wouldn’t otherwise be able to do.”

Beetroot juice seemed to widen blood vessels, reducing blood pressure and allowing more blood flow and affected muscle reducing the amount of oxygen needed during activity.

In 2009, Peninsula researchers found drinking beetroot juice could have a powerful effect on stamina and endurance, as well as lower blood pressure.

The researchers, from the University of Exeter and the Peninsula Medical School, also in Exeter, recruited eight healthy young men to complete a series of cycling tests.

They took them twice -- after drinking beetroot juice once a day for six days and after drinking blackcurrant cordial.

When tasked with cycling at an easy pace, the men used less oxygen after drinking beetroot, suggesting their muscles were able to do the same amount of work while spending less energy.

When they were asked to cycle for as long as they could before stopping, the beetroot juice allowed them to pedal an extra minute-and-a-half before running out of energy.

This 16% increase in endurance could mean someone who normally runs out of steam after jogging for an hour would be able to keep going for an extra 10 minutes.

 From the April 26, 2012, Prepared Foods’ Daily News