There's reasons to believe the supposedly adequate levels of vitamin D according to authorities are way too low. Additionally, it seems the risks of overdosing

There's reasons to believe the supposedly adequate levels of vitamin D according to authorities are way too low. Additionally, it seems the risks of overdosing (for that particular vitamin) have been greatly exaggerated in two ways: not only are dangerous levels much higher than recognized, but the effects are milder. Other fat-soluble vitamins can be dangerous in high doses, which may be part of the reasons for this (likely) mistake. What we have is the typical conundrum of opportunity cost of not using vs. risks.