That’s actually a tougher question than it might seem…
For starters, the effects of dietary nitrate on endurance exercise performance are rather small (~2%) , and seem to be reduced/absent the fitter you are. So, while, e.g., Kipchoge might tout the benefits of beetroot juice, it probably isn’t helping his marathon time any.
The effects of dietary nitrate on maximal neuromuscular power are clearly larger (i.e., 5-10%), and even trained athletes seem to benefit. Even so, I and others working in this area believe that the real target population for supplementation are individuals in whom nitric oxide bioavailability is reduced, e.g., patients with heart failure, elderly men and women.
As for the source, we just submitted a speculative mini-review titled “Beetroot juice and exercise performance: is there more to the story than just nitrate?”. The answer is, it isn’t clear, but all five of the exercise-related studies that have compared beetroot juice to a nitrate salt have reported that beetroot juice is superior in one way or another. Unfortunately, all of these studies suffer from significant limitations, such that it is difficult to draw any conclusion other than, “more research is needed”. We provided specific recommendations for how to improve studies of this issue in the summary (starting with actually measuring the nitrate concentration of the beetroot juice, something that far too few investigators actually do). (In terms of the blood pressure lowering effect, it seems to be all about the nitrate.)
I am not aware of any studies evaluating the ergogenic potential of organic nitrateS, i.e., drugs like TNG. However, they act via a different mechanism, so aside from accessibility, side effects, etc , really aren’t comparable to beetroot juice.
Finally, while there now a zillion products out there attempting to capitalize on the research that has been performed using beetroot juice, most don’t live up to their claims re. nitrate content. Thus, my standard advice for those who choose to supplement remains:
“Take two shots (of Beet It!) and call me in the morning.”
OTOH, my cardiologist colleague’s advice re. palatability is to treat it like a bad red wine: keep it really cold and drink it really fast.