[marcosdumay]

> It's a classic p-hacking trick

It's a hypothesis seeking study. It just invalidated 8 of them and picked 1 ok-ish candidate to run an actual study in.

The only thing wrong here is there's only one format for submitting a paper.

[medymed]

And if the 1 ok-ish candidate study turns out to have significant results, publication bias has to be considered: that dozens or more other studies of vitamin D (or whatever) may have not found significant results of previously ok-ish hypothesis candidates and those negative studies are often not published.

I think this is quite the case for vitamin D which has multiple physiologic roles and is studied extensively for relation to many categories of health issues. One more reason why it can be stunningly impressive when something/anything health-related is eventually proven.

[dlcarrier]

Vitamin D is a also an indicator for sun exposure, which has a myriad of health effects, so vitamin D levels are often correlated with a lot of unrelated variables that need to be accounted for.

[Aurornis]

> It's a hypothesis seeking study.

No, it was not.

It was a post-hoc analysis of a different study:

> This is a post hoc secondary analysis of the blinded, placebo-controlled Copenhagen Prospective Studies on Asthma in Childhood 2010 RCT conducted from March 4, 2009, to November 17, 2010.

Also to address this point:

> It just invalidated 8 of them and picked 1 ok-ish candidate to run an actual study in.

I don't quite know what you're talking about, since there were 11 measures looked at in this analysis and many of those measures were somewhat overlapping (various memory tests), so it's dubious to claim that the 1 significance they found means something as opposed to being an outlier they cooked up after shaking up the study data enough different ways.