Vitamin D is a fat-soluble vitamin that comes in two forms: cholecalciferol (vitamin D3) and ergocalciferol (vitamin D4) (vitamin D2). Vitamin D is added to a variety of meals, including milk and cereal. Other dietary sources include fish liver oils, fatty fish, and vitamin D-supplemented eggs from hens. The changes in chemical structure between the two forms of vitamin D have no effect on metabolism or clinical reactions once activated within the body. Although animal research have shown that vitamin D3 is less harmful than vitamin D2, human studies have proven inconsistent. 1 Vitamin D is necessary for optimal bone growth and mineralization and is essential for proper calcium and phosphate balance. Patient-specific dose can be estimated by testing serum 25-hydroxyvitamin D [25(OH)D] concentrations, which represent all vitamin D sources (e.g., sunlight and dietary or from supplements). Although cholecalciferol is approved for use in a variety of diseases, its principal application is vitamin D replenishment, as well as the prevention and treatment of vitamin D insufficiency and rickets.

NOTE: Nutraceuticals are promoted in the United States under the Dietary Supplement and Health Education Act of 1994. (DSHEA). As a result, nutraceuticals are not subject to the same regulations as medicines; scientific evidence supporting stated benefit(s) is not always accessible for nutraceuticals. Consumers should also be aware that strict quality control requirements are not necessary for nutraceuticals, and significant fluctuation in both potency and purity can occur.