Vitamin D supplementation has for some time been suggested as a falls prevention strategy for older people, but there remains an evidence gap with respect to the best dosing approach: researchers have recently compared the effects of four different doses of vitamin D3 supplements on falls. Nearly 700 people aged 70 years and older, with elevated fall risk and a serum 25-hydroxyvitamin D [25-(OH)D] level of 25 to 72.5 nmol/L were randomly assigned to receive a daily dose of 200 IU (control), 1000 IU , 2000 IU , or 4000 IU of vitamin D3, with a dose-finding stage, to determine the best non-control dose for preventing falls. After dose finding, participants previously assigned to receive non-control doses received the best dose, and new enrollees were randomly assigned to receive 200 IU/d or the best dose. The primary outcome was time to first fall or death over two years.

During the dose-finding stage, the primary outcome rates were higher for the 2000- and 4000-IU/d doses than for those receiving the 1000-IU/d dose. In the confirmatory stage, event rates were not significantly different between participants with experience receiving the best dose (events and observation time limited to the period they were receiving 1000 IU/d; n = 308) and those randomly assigned to receive 200 IU/d (n = 339) (hazard ratio [HR], 0.94 [95% CI, 0.76 to 1.15]; P = 0.54). Analysis of falls with adverse outcomes suggested greater risk in the experience-with-best-dose group versus the 200-IU/d group (serious fall: HR, 1.87 [CI, 1.03 to 3.41]; fall with hospitalization: HR, 2.48 [CI, 1.13 to 5.46]). The researchers conclude that for older people with elevated fall risk and low serum 25-(OH)D levels, vitamin D3 supplementation at doses of 1000 IU/d or higher did not prevent falls compared with 200 IU/d. Moreover, there were safety concerns with doses of 1000 IU/d. In this case, perhaps less is better? See the details for this study here.