The article opens with the observation that southern states had lower cancer rates due to solar irradiance. But then we intervene by taking pills. Why not try to absorb through the skin, even if it means something like a tanning bed?
Nobody will run that trial though because we've spent decades telling people the sun is dangerous and gives you cancer (both things can be true of course). Putting people in the sun every day would not pass ethics tests.
Also you cannot sell sunlight.
Don't give them ideas.
Australia has tried to explain sun safety here, taking into account that Vitamin D is best obtained from sunlight:
https://www.cancer.org.au/cancer-information/causes-and-prev...
I'd be interested to know a curve, i.e. at UV index 8, 3 minutes exposure, at index 6, 10 minutes exposure, etc. Maybe with a scaling for skin tone. It seems like either this kind of study has never been done (perhaps for ethical reasons) or else the information is not being disseminated. The latter seems to happen often in the medical space for paternalistic reasons, which honestly make sense for the broad public but it should be available for people to find who are motivated and have a deeper interest anyway.