If your an athlete that wants a boost in performance, particuarly endurance you may want to experiment with beetroot juice. A study in 2009 by Bailey et al. in the Journal of Applied Physiology showed that participants supplementing with .5 liters of beetroot juice for 6 days experienced a remarkable increase in perfromance.
The study measured 8 males cyclist’s time to exhaustion during intensive cycling and found that the participants who used beetroot vs the placebo were able to ride for 92 seconds longer. Also when they exercised at moderate intensity the amount of oxygen they used was decreased by 19 percent. The researchers believe beetroot juice’s high level of nitrates may be converted to nitric oxide in the body allowing better blood flow to skeletal muscles.
Like all studies there could be a number of flaws, and there is a large confounding variable. My advice would be to experiment with beetroot juice before a week of heavy training, and see if it helps. Take one cup of beetroot juice daily for a week. During this time make sure you record if your making progress, and mentally note whether it has any negative gastrointestinal effects. If you don’t mind the taste or the purple color it turns your feces, then feel free to use this drink in moderation.