Vitamin D won’t get drug company attention because no one can patent it and charge billions, but research has emerged in recent years showing a wide variety of positive effects for Vitamin D, and it’s especially important for those in the winter at northern latitudes, who are often deficient.
The medical community at large has been slow to take this up, do your own research here, you might like what you find. The Vitamin D Council is one credible resource.
I use a Vitamin D spray offered by Dr. Joe Prendergast (I buy it, no free samples or relationship there). I don’t know if the spray is sold to the public at large via mail, but you can try. I’ve also used the capsules from Bio Tech Pharmaceuticals. I'm rarely sick anymore, and I think the Vitamin D contributes to my health. I’m a natural skeptic of most supplements, but Vitamin D3 is one that has me convinced of its value.