Mark – also worth mentioning is that cholesterol is a precursor to vitamin D production, which is another reason that the demonization of cholesterol is misguided.

surplusj: I would ditch the SPF 15 in winter unless you live on the equator or something. I don’t think you need it. (Good luck finding sunscreen-free moisturizer, though. I gave up makeup, except for special occasions, because they all have sunscreen.) I’m hesitant to comment further on sunlight and skin cancer, though. And I remember learning from my high school earth science classes twenty years ago that UV rays do not pass through glass, which is why you can’t get a sunburn from sitting in a sunny window. Plants don’t use UV rays; they use, IIRC, red and blue wavelengths, which do pass through glass.

So what do I do if I want vitamin D, but also want to protect my pale, pale skin from the skin cancer that two of my grandparents have developed (and, okay, also from wrinkles)?

YES. UVA rays promote melanin production that gives our skin that tanned look. UVB rays stimulate vitamin D production, but too much exposure burns the skin. Virtually all sunscreens block UVB (SPF rating reflects UVB protection), friend of vitamin D, and full-spectrum sunscreens also block UVA.

Also, since plants can get what they need from the sun through windows, can we get some of the benefits that way, too? We have a big sunny kitchen at work, but at street level (NYC) there isn’t much that makes it through the tall buildings.