There was an actual randomized trial that came out recently [1] where hospitalized patients were given extremely large doses of Vitamin D (explanation of equvalent doses [2]) and it dramatically reduced ICU admission.

This supports the idea that Vitamin D helping with COVID is probably causal rather than just a correlation.

[1] https://www.sciencedirect.com/science/article/pii/S096007602...

[2] https://chrismasterjohnphd.com/covid-19/finally-confirmed-vi...

One should not leave out the important part "pilot study". As said by the authors in the conclusions themselves, it still requires a larger one to give definite answer.

I agree that a larger N would be preferable, but the effect size was enormous, and so the P value was <.001. Therefore, IMO, it's very likely that Vitamin D has a causal effect. Given that Vitamin D has at least some causal effect, it's much more likely that the observational studies that show a correlation are due to causation.

I would be interested to know if supplementation with Vitamin D + Vitamin K2 is more effective in improving survivability.

They measure obesity and find it 0.02 vs 0.01 for vitamin d, which seems a decent enough proxy for lifestyle for this kind of study so your underlying point is valid here. Actually i think the biggest missing control is race.

I went in skeptical even though intuitively being deficient in vitamin d makes sense, this isn’t convincing but I agree with with their conclusion that it’s worth a bigger study.

If someone reading is wondering whether to maintain a healthy level of vitamin D to help if you get covid, yes you should. Should have done that before this study ofc.

Race can be a proxy for the amount of melatonin, which influences vitamin D. It can also be related to many other things. How would you use race to interpret the data?

control for it if you are making claims about vitamin d