I don’t know if vitamin D prevents cancer, but I’ll tell you something I learned when I moved up north: don’t ever let your body run low on vitamin D, because when you do, you feel like death is imminent. I mean literally! You feel like dying. It’s all shades of terrible.
When it happened to me, I even told my kids I thought it was the end of the road for me and they should prepare. Then I went see the doctor, got my blood levels checked, and he said “Of course you feel like shit! Your vitamin D level are way down.”
Long story short, after 3 days of taking 100µg vitamin D supplements, it completely disappeared.
Don’t do like I did: don’t ever run low on vitamin D: you won’t know what’s happening to you if you don’t know the signs and it feels horrible.