[dcolkitt]

> Why not just tell people to supplement vitamin D instead?

One very consistent pattern with vitamin D research is that association studies will find a major relationship between serum vitamin D and some health outcome.[1] But an RCT using vitamin D supplementation will find no effect.[2]

That strongly suggests that serum vitamin D, at least as we measure it, is merely proxying for something else. The map is not the territory. There's an X-factor that's related to serum vitamin D, but is not just serum vitamin D. Artificial supplementation doesn't work. Since the vast majority of population vitamin D variance is related to sun exposure, that would strongly suggest that sun exposure is the X-factor that improves health.

[1]https://www.cambridge.org/core/journals/proceedings-of-the-n... [2]https://jamanetwork.com/journals/jamacardiology/article-abst...

[qvrjuec]

The only reasonable conclusion you can draw from the two studies linked is that vitamin D supplementation to increase serum levels does not significantly prevent CVD. I could just as easily hypothesize that the physical activity required to go outside both increases serum vitamin D and lowers CVD risk.

Just to be clear, I agree with your thought that sun exposure probably carries benefits beyond an increase in serum vitamin D based on anecdotal experience... I supplement vitamin D rigorously, but being in the sun just makes me feel better