Vitamin D, also known as the “sunshine vitamin”, is an essential fat-soluble vitamin for key functions in the body. Although we call it a vitamin, vitamin D is actually a hormone for regulating calcium and bone metabolism. Often recommended to people taking calcium supplements for growth spurts or old age, adequate vitamin D is necessary for calcium absorption and maintenance of healthy calcium plasma levels. Besides bone support, vitamin D also plays many other important roles in the body, including modulation of cell growth, neuromuscular and immune function and inflammatory support.†

So what type of vitamin D should you be having? Vitamin D as dietary supplements come in 2 forms: Vitamin D2 (synthetic ergocalciferol) and Vitamin D3 (natural cholecalciferol).

Despite an emerging body of evidence suggesting greater bioefficacy of vitamin D3, pharmaceutical prescriptions in North America is often vitamin D2. Clinical studies show vitamin D2 potency is less than one third that of vitamin D3 and has a shorter duration of activity. For example, 50,000 IU of vitamin D2 may be similar to a dose of 15,000 IU of vitamin D3. Vitamin D2 shouldn’t be thought the same as D3—there are big differences in their efficacy at raising serum 25-hydroxyvitamin D, reduced binding of vitamin D2 metabolites to vitamin D binding protein in plasma, and distinct differences in metabolism. Unless you are a strict vegan/vegetarian, vitamin D3 is the way to go.