Great point about the UVB index—that would be super useful info to have during winter!

I hear you on sun being the best source. The problem for those of us up north is that above ~35° latitude, the sun's angle in winter literally can't produce vitamin D, even on sunny days. The UVB rays just don't penetrate at that angle. So it's basically sun in summer, supplements in winter, or risk deficiency.

Haven't looked into the fructose/vitamin D connection—that's interesting though! Got any studies on that? Sounds like a potential rabbit hole.

Thanks for the comment!