Vitamin D, which we produce naturally from sun exposure, is essential to the healthy functioning of every organ in the body. Vitamin D deficiency has become an epidemic of modern indoor living, so a supplement is necessary. Look for naturally sourced (from lanolin or fish liver oil) Vita min D3 (cholecalciferol) , which is the type of Vitamin D made in skin in response to sunlight. It is more biologically active than Vitamin D2 ( ergocalciferol ). However, it is NOT vegetarian. Vegetarians should use Vitamin D2, which is derived from plant sources and will be labeled "vegetarian vitamin D." For the latest research on Vitamin D, go to .