The Effects of Four Doses of Vitamin D Supplements on Falls in Older Adults

Randomized, two-stage dose-finding and confirmatory study in community-dwelling adults aged 70 years and older at elevated fall risk with low serum 25-(OH)D. Participants were recruited from two Maryland sites, Hagerstown and Woodlawn, and followed for fall and hospitalization outcomes over 2 years.

Oral vitamin D3 (cholecalciferol) was tested at 200, 1000, 2000, and 4000 IU daily for up to 2 years. The 200 IU/d regimen served as the control dose during the dose-finding stage, and participants in the noncontrol groups were later switched to 1000 IU/d as the best-dose regimen.

Vitamin D3 supplementation at 1000 IU/d or higher did not reduce falls compared with 200 IU/d in this older, fall-prone population. In the primary comparison, time to first fall or death was not improved with 1000 IU/d versus 200 IU/d: HR = 0.94 (CI 0.76-1.15), P = 0.54. Higher-dose regimens raised safety concerns, with more first serious falls (HR = 1.87 [1.03-3.41]) and more first falls with hospitalization (HR = 2.48 [1.13-5.46]) versus 200 IU/d. Mean total 25-(OH)D at 3 months increased across dose groups to 67.1, 80.3, 87.3, and 119.2 nmol/L, but this biochemical response did not translate into fall prevention benefit.

The trial used a complex two-stage design with dose switching, which makes long-term dose comparisons less straightforward. Baseline demographic and lifestyle details were largely cohort-wide rather than arm-specific, and the findings come from a specific high-risk older adult sample at two Maryland sites, limiting generalizability.