Living in the southern hemisphere (the one with the bigger ozone hole) and being an import from dark cold places I turn into a lobster with moderate sun exposure. It doesn't always get better heading away from the equator here due to ozone depletion.

Adding computers, air conditioned comfort and a complete disinterest in outdoor activities to the mix and I doubt if I get enough vitamin D to last me through the winter. Skin cancer avoidance is well understood here and drilled into kids from pre-school age but lifestyle changes may be putting some people into other risk areas.

Curiously, I have a skin condition that is treatable by UV exposure, topical vitamin D analogues and generally improves in summer yet as far as I know there is no clinical evidence that vitamin D supplements have any benefit.