Sunscreen. When? Why? Why not?

If you're worried about Vitamin D deficiency, it's quite easy to supplement. Why not do that (IF you're deficient) and wear sunscreen?

As someone who actually tries to follow dermatological recommendations for sunscreen use, it's pretty hard. You have to remember it every time you leave the house, be motivated enough to go through a tedious and bad-smelling task, cover *all* the exposed skin. If you're outside for a significant time, you have to remember to bring the sunscreen and reapply every hour. So, it's hard to believe that most people who spend time outside and wear sunscreen are actually doing it enough to avoid D exposure.

My read of the research is that the controllable risk factors for D deficiency are never going outside + poor diet + not supplementing, rather than overzealous sunscreen use.

A short answer is "Don't worry about Vitamin D unless you have a deficiency, avoiding UV damage to skin is more important". This doesn't necessarily mean sunscreen, could be taking a siesta during the peak UV times, wearing a proper hat and clothing etc. Something basic like staying out of the direct sunlight between 10am and 3pm ( more if you are in tropics or subtropics) would give you an approximate balance. If in doubt, there are plenty of UV meters on the market that would help you be more quantitative.

(fixed the formatting a bit. if you want to use the markdown editor, go to your settings and check the box for that, but by default you can just hover over text and click the link button to put a link behind some text.)

In the southern states, the sun feels hotter. People don't go out in the sun for a long time without sunscreen. In the northern states people think they are more fine. Consequently get more cancer. Also these results are slow to fruition because skin cancer takes a lifetime to develop.