2.2 Vitamin D Metabolism and Sources of Vitamin D for Infants: The Canadian Scenario Endogenously synthesized vitamin D is in the form of cholecalciferol (vitamin D3). Most food sources and supplements in Canada have this mammalian form, but some contain the plant form, ergocalciferol (vitamin D2). Vitamin D3 is estimated to be approximately 9.5 times more potent than vitamin D2 (12).