Another Comparison of Vitamin D₂ and Vitamin D₃ Supplementation

Vitamin D that is produced naturally from sunlight exposure is vitamin D₃. However, both D₃ (cholecalciferol) and D₂ (ergocalciferol) are available as supplements. In the U.S., supplemental vitamin D₂ is usually a 50,000 IU prescription medication, whereas D₃ is available over-the-counter in various doses. With D₃ supplementation, essentially all measured serum 25-hydroxyvitamin D (25[OH]D) is hydroxylated D₃. In contrast, with D₂ supplementation, total serum 25(OH)D is the sum of supplemental D₂ plus endogenous D₃. Some, but not all, studies have suggested that supplemental D₃ raises total serum 25(OH)D more than supplemental D₂ does (NEJM JW Gen Med Apr 26 2011).

Researchers randomized 107 healthy volunteers in a northern German community …