Vitamin D is a fat-soluble hormone involved in the intestinal absorption of calcium and regulation of calcium. It plays a vital role in the formation and maintenance of strong, healthy bones. Vitamin D deficiency has long been associated with rickets in children and osteomalacia in adults, and long-term insufficiency of calcium and vitamin D leads to osteoporosis. However, in recent years, vitamin D levels has become known as an indicator of general health status, and there have been multiple publications linking insufficient levels of vitamin D to several disease states, such as cancer, cardiovascular, diabetes, and autoimmune diseases.1
1 Dietary Supplemental Fact Sheet: Vitamin D. Office of Dietary Supplements. National Institutes of Health. Updated 11/13/2009. Accessed 08/17/2010.