There is a pretty fair amount of anecdotal evidence that vegetable oils, because the fats become part of our mitochondria cell walls, subject a person to sun burn more than if a person eats mostly or only animal fats for fat consumption. I am one of those anecdotes and have noticed that I really just don't get sunburned as easily as I would have in the past.

I agree with you on the nudity and exposure. It really only takes a half hour or maybe an hour of summer sun on most of the body to get tons of vitamin D. During the 3-4 months we are in Bonaire in the winter I will sit in my speedo out on a beach chair for a half hour. Here at home in the summer I often keep covered up with a long sleeve shirt and long pants. So in all reality, I probably get more vitamin D from the sun during the winter months than in the summer here at home. But I think ideal would be a half hour in the morning sun (relative low angle so different UVA vs UVB) mostly naked.

Some doctors think there may be benefit from sun exposure that we just don't yet know about completely independent of vitamin D.

People have been made afraid of sun exposure because of skin cancer. Yet there have been multiple studies that show that people that tend to be outside more (more sun exposure) actually have longer life spans and lower rates of skin cancer than people that tend to be inside more. Of course there could be many confounding cofactors to studies like that, but an interesting observation nonetheless. 

One piece of information I ran across about sunscreen was that it blocked out the rays that gave us vitamin D yet let the harmful rays pass through. So there was question if there was even a benefit. I can never remember which is the harmful one as far as exposure and skin cancer goes, UVA or UVB. Would not be the first time we were led astray by lots of advertising and bad information. Wife and I completely quit using sunscreen shortly after we went low carb (and cut out the vegetable oils) and have not found the need for it since. But that is just our experience. Others experience may vary.