Vitamin D is a fat soluble vitamin and comes in twp relevant forms of vitamin D - D2 and D3. D3 is produced by your body after exposure to ultraviolet B light (either natural or artificial). It can be found in foods such as fatty fish, eggs, and some meats. When metabolized by the body it is used to help the body control levels of calcium and phosphate, growth and rebuilding of bone, and defending the body against some microbial invaders (germs). Some recent research also suggest that vitamin D may provide protection from high blood pressure, certain forms of cancers, certain autoimmune diseases, and possibly osteoporosis.