In a recent study, cyclists drank beet juice or a placebo for six days. The next day they rode for an hour and then raced a 10-K time trial. Those who drank beet juice rode faster, cycled harder, and used less oxygen during the trial. Researchers credit the athletic boost to nitrate found in beet juice, which indirectly increases blood flow.
A recent study found drinking two cups of beet juice (which has a high nitrate level) daily for six days may decrease the oxygen your muscles need, thus improving endurance.