Here is an article from Dr. Mercola on some of the latest studies on Vitamin D.
If You Take Oral Vitamin D You MUST Avoid Making This
Serious Mistake
By Dr. Mercola
Did you know there are two types of vitamin D, and they are NOT
interchangeable?
In fact, taking the wrong one could do you more harm than good… Drisdol is a synthetic form of vitamin D2—made by irradiating fungus and plant matter—and is the form of vitamin D typically prescribed by doctors. This is not the type produced by your body in response to sun or safe tanning bed exposure, which is vitamin D3.
A recent meta-analysis by the Cochrane Database looked at mortality rates
for people who supplemented their diets with D2 versus those who did so with D3, the form naturally produced by your body, highlighting the significant differences between the two.