I am a bit perplexed. Haven't almost all randomized/controlled trials shown (e.g. [1]) that there is basically no measurable effect for healthy people? All "positive" stories are relying on observational studies with the usual confounders, right?

EDIT: Look at figure 2 in the Paper. Looks pretty random to me. Result is almost exclusively driven by 4-5 small (<250 participants) and old studies.

[1] https://www.vox.com/2018/10/4/17933880/vitamin-d-health-sun-...