Comparing the segment of the general population with the lowest vitamin D to the highest, the odds ratio for all-cause mortality is 1.9[1]. In other words peopl

Comparing the segment of the general population with the lowest vitamin D to the highest, the odds ratio for all-cause mortality is 1.9[1]. In other words people with low vitamin D are almost twice as likely to die as those with high vitamin D. That means that at least from an association standpoint, vitamin D deficiency is as predictive of poor health as smoking vs. non-smoking status.[2] Imagine the existence of a health intervention that is just as effective as stopping smoking, that consisted of a $0.10 pill taken once a day. It's worth shouting from the rooftops. Now there are certainly reasons for apprehension. And of course correlation does not always mean causation. In particular supplementation does not seem to directly lower mortality. However sun exposure does seem to directly lower mortality. That suggests the possibility of an unidentified sub-type of vitamin D or other micronutrient related to sun exposure that is driving lower mortality. (In which case serum vitamin D would be acting as a proxy for sun exposure.) [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4103214/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4103214/ [2] https://www.ncbi.nlm.nih.gov/pubmed/22688992 https://www.ncbi.nlm.nih.gov/pubmed/22688992