Let's face it - who would spend the money to fund a study on a substance that's been around for hundreds (thousands?) of years?
Probably if you're going to spend the money to investigate it, you expect some kind of return. So sadly, all these studies end up being funded by people with an interest in a positive outcome.
The bigger question to me is, does that immediately invalidate their results?
It warrants skepticism of the strongest variety unless the study can be reliably replicated under better circumstances. Don’t be shocked when it doesn’t happen though.
Like alcohol studies paid for by brewers, this is hard to accept at face value given the knowns. Even when money isn’t pulling the strings, nutrition studies are notoriously unreliable by dint of human variability and the nature of the studies themselves.
I wouldn't be surprised if around 90-95% of special interest funded studies that aim for a p value of <5% aren't published.
This is true of the majority of publicly-funded research, too.
How many times did they fund this study with different research groups, quietly round filing the results each time until they found a research group willing to p-hack a flattering result?
“You are young yet, my friend,” replied my host, “but the time will arrive when you will learn to judge for yourself of what is going on in the world, without trusting to the gossip of others. Believe nothing you hear, and only one half that you see."
Considering that most such research results are already non-reproducible and p-hacking, the added vested interests land this squarely in the crap category.
People like us nerds thinking it through strict logic ("still this does not necessarily invalidate") might reduce some false negatives, but it mostly just wastes our time and has us taken for suckers from industry/marketing con men. With this kind of "research" taking a shortcut in its evaluation is more productive.