Beetroot juice was claimed as the elixir of sporting life by some athletes at the London Olympics.

Paralympic superstar, David Weir, drank it during his winning wheelchair marathon race. But what’s the truth?

Andy Jones, professor at the sport and health sciences department at Exeter University, says the active ingredient is nitrate, a nutrient found in soil that helps build protein. This converts into nitrite in the body and then into nitric oxide, which has a “double whammy” effect, widening blood vesselsand increasing blood flow. it also reduces the oxygen needed by muscles, enabling them to work more efficiently.

Jones says, “We found this works most effectively in high-intensity exercise, typically races that last up to 30 minutes”. However, the average runner might feel the benefits of beetroot more than elite athletes whose muscles are already efficient.

So if you are far below top level, but still want to beat your personal best, try beetroot juice. Experts say the best way to get the benefits is to drink the juice.

“Shots” containing 7cl of concentrated juice, and 0.4g of nitrate, have been developed as a sports drink and for use in studies, by the James White drinks company in Ipswich. Managing director Lawrence Mallinson, who supplied shots to Team GB, says that beetroot juice now accounts for half of the firm’s £5 million turnover.

You would need to drink about 500ml (half a litre) of ordinary strength juice to get the same nitrate levels.