Objectives: to determine whether vitamin D supplementation reduces the risk of fracture or falls in elderly people in care home accommodation.

Design: a randomised controlled trial of cluster design.

Setting and subjects: 223 residential units (mainly identical 30-bedded units), within 118 homes for elderly people throughout Britain, with 3,717 participating residents (76% women, average age 85 years). The units provided mainly or entirely residential care (35% of residents), nursing care (42%) or care for elderly mentally infirm (EMI) residents (23%).

Methods: participants were randomly allocated by residential unit (cluster design) to a treated group offered ergocalciferol 2.5 mg every 3 months (equivalent to a daily dose of 1,100 IU), or to a control group. Fractures were reported by staff and confirmed in hospital, and routinely collected data on reported falls were obtained.

Results: after median follow-up of 10 months (interquartile range 7–14 months), 64 (3.6%) of 1,762 vitamin D-treated residents and 51 (2.6%) of 1,955 controls had one or more non-vertebral fractures, and 24 (1.3%) and 20 (1.0%), respectively, had a hip fracture. The proportion reporting at least one fall was 44% in vitamin D-treated and 43% in control residents. The differences between the vitamin D and control groups were not statistically significant. The incidence of all non-vertebral fractures in the care homes (3.2% per year) and of hip fractures (1.1% per year) was low, similar to rates in elderly people in sheltered accommodation, and the pre-treatment serum 25-hydroxy vitamin D concentration was high [median 47 nmol/l, measured in a 1% (n = 18) sample].

Conclusions: we found no evidence that vitamin D prevents fractures or falls in elderly people in care home accommodation.