My understanding is that it’s extremely hard to get large scale controlled studies on sun exposure vs vitimin d supplementation, so there is lots of uncertainty still on relative efficacy. I wouldn’t say certainly that it’s inferior to sun exposure, but sun exposure can clearly have many more effects than just stimulating production of vitimin d that could then appear to correlate with D serum levels.

Some more reading specifically on vitimin D:

https://ods.od.nih.gov/factsheets/VitaminD-health%20Professi...