High-Dose Vitamin D: Helpful or Harmful?

If the optimal serum 25(OH)D level for skeletal health is 30 ng/mL or greater, then vitamin D insufficiency is widespread, affecting about 75% of adults based on a recent survey of more than 20,000 Americans. However, after a comprehensive analysis of existing research studies, the Institute of Medicine recently concluded that nearly all individuals are vitamin D replete when their 25(OH)D levels are 20 ng/mL or greater. Furthermore, two recent publications challenge the belief that 25(OH)D levels greater than 30 ng/mL are optimal for bone health. In a randomized, placebo-controlled trial, high-dose, once-yearly vitamin D therapy increased the incidence of fractures and falls. The second study reported that high-dose vitamin D did not reduce levels of parathyroid hormone or bone resorption among adults with 25(OH)D levels less than 32 ng/mL at baseline. It is time to question whether serum 25(OH)D levels of 30 ng/mL or greater are necessary for all individuals.