Medicine is going to become more and more personal as we enter the age of AI. Vitamin D may be beneficial for certain individuals but may not show any significance in major populations. The same thing as diets, certain drugs, and other vitamins/minerals. What I find saddening is that certain researchers will jump straight into a RCT of vitamin D for upcoming diseases as if that will do anything of significance. There are some devout vitamin D followers out there just like there were with vitamin C. One of the biggest risks of vitamins is contamination similar to the tryptophan incident in the 90s. Nobody has to prove safety or efficacy to sell them although they are generally safe to use until some accident happens and they aren’t.