Apparently, many such coffee studies are sponsored by firms with an interest in publicizing coffee's benefits. It doesn't mean the science necessarily isn't good. Although, consider the opportunity cost: we could instead be researching many other things that don't carry as high a cost as coffee (in terms of production labor, refining, and transportation), and may commute even greater benefits. Of course, we shouldn't expect big corporations to sponsor that kind of research, because it's not in their interest.

It is decidedly in the interest of coffee conglomerates to demonstrate that coffee is good for society, because it justifies the great fiscal and human expenses they go to, to bring fresh coffee to your breakfast table. Not passing judgement either way, it's just an interesting lens to consider.

There was a nice article in the new yorker a couple months ago on the subject of society's shifting moods towards coffee, and how it's materialized in the literature and science. https://www.newyorker.com/magazine/2020/04/27/the-war-on-cof.... One of the reviewed books: https://www.amazon.com/Coffeeland-Mans-Empire-Making-Favorit....

Edit: oh boy. I misread the parent comment. I thought they had declared a conflict of interest. Sorry. I didn't intend for my comment to read as a corporate-research apologia.