alt Hacker News> Being generally active and eating fruits/vegetables is like 80% of the work for being healthy.
Except for the things that you get from sunlight, not diet.
> If everyone is deficient, then it must not be that important.
But nobody who lives in e.g. East Africa and spends a lot of time outdoors is deficient.
So it's actually pretty reasonable to say that a modern indoor lifestyle combined with long winters would truly lead most people in those regions to being deficient.
If everyone is deficient, how would you even establish a baseline of what counts as deficient and excessive? The way they do that is they sample the population and look at the ranges of the values and maybe look at when comorbitity issues arise within those ranges. But “everyone is deficient in X” is easily dismissed hokum.