And indeed, it seems they did survey for sun exposure and include it in their analysis, and they caveat a lot of their references to other work in their introduction noting where other studies didn't.
https://www.naturalhealthresearch.org/wp-content/uploads/202...
The issue with this is that the amount of vitamin D someone might take is correlated with how much sun exposure is available. And the amount of available sun exposure can impact what is considered a little / a lot to each person.
> The issue with this is that the amount of vitamin D someone might take is correlated with how much sun exposure is available. And the amount of available sun exposure can impact what is considered a little / a lot to each person.
That could be case but not necessarily in this study.
This would immediately kill about half of the comments on any research article posted to HN.