High-Dose Vitamin D Supplementation: Too Much of a Good Thing?

Many randomized controlled trials indicate that vitamin D will reduce falls and fractures. Therefore, the hypothesis in the study by Sanders et al¹ in this issue of JAMA, that a single annual 500 000-IU oral dose of cholecalciferol (vitamin D₃) would be effective in reducing falls and fractures in older women with 1 or more risk factors for falling was a reasonable one. However, not only was this regimen not effective in lowering risk, it also increased risk of falls and fractures, with the greatest increase occurring during the first 3 months after dosing. An increase in fractures but not falls was reported in another trial in which high-dose ergocalciferol was given intramuscularly each year to men and women 75 years or older.²