The specific compound to use for vitamin D supplementation is often ambiguous. The term ‘supplementation’ has been used in relation to cholecalciferol, ergocalciferol, calcidiol, and calcitriol. But which is the ‘real’ vitamin D? An article in the European Journal of Clinical Nutrition clarifies just that.
The natural form of vitamin D is cholecalciferol, also known as vitamin D3. In contrast, ergocalciferol, also known as vitamin D2, is primarily a synthetic and less stable product which is less potent per microgram than cholecalciferol. Calcidol is the major circulating metabolite of cholecalciferol, while calcitriol is the hormone that upregulates the transport of calcium from the gut, and suppresses parathyroid hormone secretion.
“Nutrition policy papers and guidelines generally do not state that calcidiol and calcitriol are not nutrients, and that those metabolites are not pertinent to food fortification or dietary supplementation,” said author Reinhold Vieth, from the Department of Laboratory Medicine and Pathobiology, and Department of Nutritional Sciences at the University of Toronto.
“It must be concluded that cholecalciferol is the only form of vitamin D that should be considered in the context of the nutritional functions of fortification and supplementation,” he said.