In theory it is not outside the realm of conventional medicine to use vitamin supplements. However doctors get so little training in the use of supplements and most of that has to do with the RDA's which are based on the amount needed to prevent gross deficiency disease rather than optimal health. Then there are the issues involved with how well any person is able to absorb any given nutrient either from whole foods or from supplements, which tests are valid ways to measure a person's nutrient status, what form of the nutrient is the most bioavailable. Most conventional medicine doctors just are not trained to give this kind of advice. Just like with figuring out what foods to eat, I have found that I have to do my own research to try to determine what supplements, if any, to take. I have found this site to be helpful:

http://lpi.oregonstate.edu/mic

Still it's mostly guess work.

Jean