I am in the medical field and I would beg to differ on the "well tested" part of prescription drugs. Many of them were tested on male populations, some are fast tracked, and many of them seem to have side effects including death!?
Have you listened to the adds on some of these newer drugs. Your psoriasis will get better, maybe 70%, but your kidneys might fail and your immune system will be compromised, etc etc etc! There are studies done on many vitamins/minerals/natural supplements. Often these are done in other countries or Learning institutions because there is no money to be gained for big Pharma. They can't patent natural. No money means less studies and more synthetics.

So this means trust the FDA and other Gov. lobbied agencies selected stamp of approval as harmless? They rubber stamp them after testing and list the possible side effects that many say including death. Sure I'll try a over the counter vitamin over those first! Nothing works for everybody, so proven is all subject to the individual, not questionable single sided test polls.
We know many trained doctors have the same view of the drugs they prescribe, let's try it and see. That makes me a willing lab rat. Why? PAIN! Despite addiction being the biggest side effect.