I’ve heard loads of good things about FCLO.
I thought this program was about feeding yourself what you crave, and not putting anything on the “no-no” list. So, if it makes you feel good, that’s good enough for me – I don’t think it can hurt, for sure.
I’m also in a northern climate, and definitely feel better when I take loads of Vit D – right now I’m finishing off some Carlson Vit D drops, but might switch it up to a D/K combo next, I hear they do better together.