Then again, there have been several studies [0] that show that many people in the northern hemisphere are deficient in vitamin D and that the deficiency could be the root of serious health problems.
True, for example half of Finns receive less than recommended amount of vitamin D. To combat this dairy and edible fat products have received vitamin D supplements since 2003. For example skimmed milk (the most popular one) would otherwise have very little D because it gets removed in the process along with fat. First you take it out, then put it back in...
[0] E.g. http://www.ncbi.nlm.nih.gov/pubmed/21310306