Vitamin D: Bolus Is Bogus—A Narrative Review

In this review we summarize the impact of bolus versus daily dosing of vitamin D on 25(OH)D and 1,25(OH)(2)D levels, as well as on key countervailing factors that block vitamin D functions at the cellular level. Further, we discuss the role of bolus versus daily dosing of vitamin D for several health outcomes, including respiratory infections and coronavirus disease 2019 (COVID‐19), rickets, falls and fractures, any cancer, and cancer‐related mortality. This discussion appears timely because bolus doses continue to be tested for various disease outcomes despite a growing amount of evidence suggesting lack of efficacy or even detrimental effects of bolus dosing of vitamin D for outcomes where daily dosing at modest levels was effective in the vitamin D deficient. As a result, these discordant results may bias health recommendations for vitamin D if the recommendations are based on meta‐analyses combining both daily and bolus dosing trials. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.