9. High-dose vitamin D supplementation in the elderly

Abstract

The vast majority of studies assessing the effect of vitamin D on a range of outcomes, provide doses of <25 μg/day to older adults. Because of the potential for enhanced convenience or compliance, there has been an interest in higher doses, though availability of high dose products in many parts of the world, particularly Australia and North America, has limited their clinical applicability. Since the middle of the last decade, there has been a rapid expansion of data surrounding efficacy and safety of high-dose interventions, in elderly and in other population groups. Such regimens include weekly or monthly doses, and larger doses administered seasonally, annually, or as loading doses to rapidly boost vitamin D status. The efficacy of high-dose vitamin D supplementation over lower-dose preparations depends on the 25-hydroxyvitamin D response to vitamin D supplementation. An examination of data surrounding the pharmacodynamic effect of oral vitamin D shows that the dose-response is highly variable and depends on factors such as basal vitamin D status, body composition, the type of vitamin D provided and the dose itself. Controlled interventions examining the efficacy of high doses in elderly have mainly investigated musculoskeletal outcomes. Evidence of high-dose vitamin D efficacy is inconclusive for fracture-and falls-risk, their musculoskeletal determinants in this population group, and for other outcomes. Whilst most studies that provide high doses of vitamin D and report follow-up measurements of calcaemic effects find little evidence of increased hypercalcemia, hypercalciuria or renal stones, relative to control groups, there are a lack of adverse effect data from large controlled investigations. A cautious approach to administering loading doses ≥7.5 mg of vitamin D might be warranted since two recent studies have shown modestly increased risk of falls and hip fractures.