It's possible that all these studies are wrong and that Vitamin D supplementation is pointless. Information is never perfect. But at this time, on the balance,

It's possible that all these studies are wrong and that Vitamin D supplementation is pointless. Information is never perfect. But at this time, on the balance, vit D supplementation seems like a pretty sensible bet for anyone living in far latitudes during winter, especially people with more pigmented skin. It looks like there's very little risk of harm, and it's cheap stuff.