What is Vitamin D

http://www.energyfirst.com/Vitamin-D : What is Vitamin D?  It is a fat-soluble vitamin which helps in the process of absorbing calcium.  It also helps with maintaining blood levels of calcium and phosphorus. Like all fat-soluble vitamins, A, D, E, and K, vitamin D is absorbed through the small intestines but unlike the others, D is also absorbed through the skin by the suns rays.