Vitamin D is essential for the proper absorption of dietary phosphorus and calcium. This absorption influences the bone mineral density that is directly responsible for fractures and osteoporosis.

The experts collected data from 11 double-blind randomized, controlled trials of oral vitamin D supplementation with or without calcium in contrast to placebo or only calcium in volunteers aged 65 years or above.
Researchers collected from 31,022 volunteers with 3770 cases of non-vertebral fractures and 1111 incidents of hip fractures. They compared and analyzed the occurrence of hip and non-vertebral fractures among the treatment group, with actual vitamin D consumption, and the control group.
An important finding of the study was that the volunteers who randomly received vitamin D showed non-significant reduction of 10 percent in the risk of hip fracture and a reduction of 7 percent in risk of non-vertebral fracture.
The benefits of high level of vitamin D intake were seen to remain consistent in the subgroups defined by dwelling type, age group, calcium intake and baseline 25-hydroxyvitamin D level.
Another important point highlighted was the role of 25-hydroxyvitamin D level above 60 nmol per liter in the prevention of fractures.
Reference:
A Pooled Analysis of Vitamin D Dose Requirements for Fracture Prevention; Heike Bischoff et al; N Engl J Med 2012; 367:40-49