Vitamin D is a fat-soluble vitamin. This Vitamin is produced by our bodies from cholesterol via process that is activated by action of ultraviolet B rays from the sun on our skin. The following factors are taken into consideration when figuring out how much of Vitamin is our body producing: skin color, age, amount and time sun exposure, and geographic location. This important vitamin can play an important role in influences of control of cell cycles, brain, muscles, pancreas, cardiovascular and immune system, intestines and bones. Its primary functions are to maintain normal blood concentration of phosphorus and calcium and to support bone health.