Consider that while you are one person, a doctor sees many patients. They see that prescribing Vitamin D helps almost none of their patients in the short term,

Consider that while you are one person, a doctor sees many patients. They see that prescribing Vitamin D helps almost none of their patients in the short term, and they can only rely on research for the long term (i.e. they are not seeing the same patient over decades). Doctors run the whole gamut. There certainly are doctors who will recommend Vitamin D for any issue under the sun. I've been subjected to that, and it totally didn't impact the issues I was going to the doctor to see. At the other end you'll get doctors who will stick to the official guideline (as long as your Vitamin D levels are "normal"). And you have those in between, who will discuss it with you, give you the pros and cons, and will support you in your decision. I've had enough doctors recommend treatments that have little backing that I'll happily take the risk and stick to the studies. ("No thanks, I won't go for that surgery which studies have not shown tackle the problem" (an assessment the doctor admitted to only when I asked him directly)). I know I'll be wrong on occasion, but I suspect I'll be wrong more often if I follow the other path. Still, you'll get all sorts of doctors, and it shouldn't be hard to find one who will happily reflect back to you whatever you want to hear. As for 30 years, the major study associating Vitamin D with mortality came out about 15 years ago.