Vitamin D, also known as the ﬁsunshine vitaminﬂ is an essential vitamin that plays many important roles in the proper functioning of the body. Though classified as a vitamin, vitamin D is actually a key regulatory hormone for calcium and bone metabolism. Adequate vitamin D status is essential for ensuring normal calcium absorption and maintenance of healthy plasma calcium levels. Besides bone support, vitamin D has many other roles in the body, including modulation of cell growth, neuromuscular and immune function. Numerous scientists now feel that supplementation with vitamin D at levels greater than previously thought necessary is critical to helping maintain healthy bone remodeling and healthy vitamin D plasma levels.