"How does who funded it affect the outcome?"
That's exactly what Mr AGreeable is shouting about. I want to know where he's found the info as google/PubMed/J App Phys isn't directly giving that info. (don't have acces to the full paper at home).
As an academic scientist myself, I'm well aware of the many claims that funding affects the outcome (i.e. test with a big pharma company's new drug is funded by them and is positive outcome, lots of shouting that the scientists wouldn't upset their sponsor by reporting negatively).
In the case of beetroot juice however the only likely sponsors I can think of are the National Agriculture lot, or a company that sells beetroot juice. Neither are likely to have the pull of a big pharma company to 'influence' results.