[jrpt]

I would like to know how regular sunlight compares to the combination of vitamin D supplementation and red light therapy. If you do both of those, is that equivalent or better since it doesn't have any damaging effects of the sun?

[setopt]

There are other benefits as well. For example, some eye exposure to violet or ultraviolet light have been shown to reduce myopia, which might be one reason why glasses usage has increased a lot. (Screen usage is a big myopia factor as well, but it’s not the whole story.)

There are also studies suggesting that low-level UV exposure lowers risk of death by more than what can be explained by serum vitamin D levels alone, suggesting other unknown mechanisms at play.

[cma]

Make sure the studies control for people bed bound for long times in the hospital or in home care, they are magnitudes more likely to die early and don't get as much sun as people doing sports etc. but the sun isn't likely to be the primary factor.

If they claim causation in the paper it is usually controlled for, if they just claim a link it might not be.

[mylifeandtimes]

something to think about here: Your body synthesizes vitamin D. That chemical reaction may have side-products which are not found in the supplements.

Biology is complex.