CRD Summary: This well-conducted review found that high-dose (at least 400 IU/day) vitamin D supplementation reduces fractures in people aged 65 or older but lower doses are not effective. The authors' conclusions follow from the high quality evidence presented and are likely to be reliable.

[Randomised controlled trials (RCTs) with a minimum follow-up of 1 year that compared oral vitamin D (cholecalciferol or ergocalciferol) supplementation (with or without calcium) with placebo or calcium alone were eligible for the review.]

CRD Commentary: Inclusion criteria were clear. The authors searched a number of databases without language restrictions and made some attempt to locate unpublished studies. Risk of publication bias was assessed. Validity was not assessed, but some quality features were used as inclusion criteria for the main analysis. Relevant details of included studies were presented. Appropriate methods were used to minimise errors and bias in data extraction, although it is unclear whether similar methods were used in study selection. Studies were pooled by meta-analysis and sources of heterogeneity were extensively analysed. The authors' conclusions follow from the evidence presented and are likely to be reliable for the population included in the trials (mainly elderly women).