There's a decent chance you'll be reading about diet soda studies until the day you die. The odds are exceedingly good it won't be the soda that kills you. But here's why the studies are unlikely to end.
If it's artificial, it's bad
People suspect that things created in a lab cannot be good. But everything is a chemical, including dihydrogen monoxide (water). Some ingredients occur naturally, and some are coaxed into existence. That doesn't inherently make one better than another.
Soda is an easy target
No one "needs" soda. We also don't need ice cream or pie, but for a lot of people, life would be less enjoyable without those things. None of this should be taken as a license to drink cases of soda. A lack of evidence of danger at normal amounts doesn't mean that consuming any one thing in huge amounts is a good idea. Moderation matters.
Publish or perish
Scientists need funding to survive, and you need to publish to get funding. Often, the easiest step is to take a large data set and publish an analysis showing a correlation between some factor and outcome.
Prestige and the press
Gathering data is more expensive and time-consuming. Thus, a few universities produce a disproportionate amount of research. They also tend to be the ones with the most resources, the most recognizable names — and get the most attention. If the research is from a super-respected institution, it must be important.
The limits of observation
For reporting on hundreds of thousands of people, observational studies are generally the only realistic option. But they usually tell us only if two things are related, not whether one is to blame (as opposed to randomized control trials).
