Objective: To determine the effect of four monthly vitamin D supplementation on the rate of fractures in men and women aged 65 years and over living in the community.

Design: Randomised double blind controlled trial of 100 000 IU oral vitamin D₃ (cholecalciferol) supplementation or matching placebo every four months over five years.

Setting and participants: 2686 people (2037 men and 649 women) aged 65-85 years living in the general community, recruited from the British doctors register and a general practice register in Suffolk.

Main outcome measures: Fracture incidence and total mortality by cause.

Results: After five years 268 men and women had incident fractures, of whom 147 had fractures in common osteoporotic sites (hip, wrist or forearm, or vertebrae). Relative risks in the vitamin D group compared with the placebo group were 0.78 (95% confidence interval 0.61 to 0.99, P=0.04) for any first fracture and 0.67 (0.48 to 0.93, P=0.02) for first hip, wrist or forearm, or vertebral fracture. 471 participants died. The relative risk for total mortality in the vitamin D group compared with the placebo group was 0.88 (0.74 to 1.06, P=0.18). Findings were consistent in men and women and in doctors and the general practice population.

Conclusion: Four monthly supplementation with 100 000 IU oral vitamin D may prevent fractures without adverse effects in men and women living in the general community.

Vitamin D and calcium supplements are effective in preventing fractures in elderly women

Whether isolated vitamin D supplementation prevents fractures is not clear

Four monthly oral supplementation with 100 000 IU vitamin D reduces fractures in men and women aged over 65 living in the general community

Total fracture incidence was reduced by 22% and fractures in major osteoporotic sites by 33%