Does vitamin D3 dosing schedule influence treatment efficacy in nursing home residents with vitamin D deficiency?

Vitamin D deficiency is a common problem among elderly nursing home residents. In this Practice Point commentary, I discuss the findings and limitations of a randomized, controlled trial by Chel et al. that evaluated the effect of equivalent oral doses of vitamin D3 given as 600 IU daily, 4,200 IU weekly or 18,000 IU monthly. Regardless of the dosing schedule, oral administration of vitamin D3 was associated with increased levels of serum 25-hydroxyvitamin D and reduced levels of parathyroid hormone in the study cohort. Daily administration of vitamin D3 was found to be more effective than either weekly or monthly administration. The addition of calcium supplementation for a 2-week period did not appreciably augment the effects of vitamin D3 supplementation. Here, I highlight the issues to consider when interpreting studies of vitamin D3 supplementation, its effect on vitamin D status, and the consequences for calcium and bone metabolism.