Beetroots are rich in nitrate and anthocyanins. Both provide health benefits but it's primarily the nitrates that give the performance benefits.
Once ingested, the nitrate is converted in the mouth by the local bacteria into nitrite.
In the acidic conditions of the stomach, the nitrite is then converted to nitric oxide, which is absorbed into the bloodstream.
Nitric oxide dilates blood vessels, which delivers oxygen more quickly to the muscles, so energy can be burned to fuel the exercising muscles.
The result is that less energy is used for performance, which means it takes longer to tire.
The Australian Institute of Sport (AIS) has assessed beetroot and classified it as a Group A supplement. This means there is strong scientific evidence for use in specific situations in sport