You can divide vitamin D supplements into two basic types. Natural ones are D3 and they contain the same vitamin D your body makes when exposed to sunshine.

However, nearly all the prescription-based supplements do not contain vitamin D3: They use vitamin D2 which is not the same. This new study from the American Journal of Clinical Nutrition encourages experts to seriously reevaluate using D2 and remove it from supplements.

Vitamin D2 was first produced in the 1920s through ultraviolet exposure of foods. The process was patented and licensed to drug companies for use in prescription vitamins. In case you didn't know, the vitamin D that is added to milk is NOT D3 but the highly inferior vitamin D2.

The important factor to remember is that vitamin D2 is only about twice as active as vitamin D3. Once either vitamin is in your body, however, it needs to be converted to the more active form and vitamin D3 is converted 500 percent faster than vitamin D2.

To learn even more about all the good vitamin D can do for your health, I urge you take this "test" developed by Dr. John Cannell. Also, with colder weather and shorter days coming soon, one of your best sources for getting the vitamin D you need is a high quality cod liver oil.

American Journal of Clinical Nutrition, Vol. 84, No. 4, October 2006: 694-697