Earlier quoted context omitted.
In the UK you can easily get all your vitamin D from sunlight for 6 months of the year[0,1]. That said, more and more foods are being vitamin supplemented, or available in fortified versions, especially for children (eg milk, yoghurts). I doubt it'll become "standard" like thiamin and others in flour (in the UK at least) because you can overdose. [0] http://www.bad.org.uk/for-the-public/skin-cancer/vitamin-d (footnot…
I recently read this paper. It says there was a major mathematical error in the meta study used to dictate the Vitamin D standards for many countries: https://www.ncbi.nlm.nih.gov/m/pubmed/28768407/
The major finding is the original targets are based on the average response (so up to 50% still in deficiency), not getting 97% to a base level.
However only being able to use 10 papers and without their data (only standard deviations) hamstrung their ability to peg a better range. More, their approach requires a normal distribution and a solid link between input and output levels, neither of which really exist here. Random error scuppers their analysis.
Again, this is not to say there isn't something here, it just needs more work, especially when recommending people take 2-3 times the current max tolerable limit.