The combination marginally reduces the risk of some types of bone fractures, but the effect appears only in those who live in nursing homes or other institutions.
"Frail older people confined to institutions appear to experience a reduction in hip and other non-vertebral fractures if given vitamin D with calcium supplements," write Alison Avenell, of the University of Aberdeen, Scotland, and her colleagues.
Vitamin D alone and calcium alone does not appear to have any effect on reducing the risk of fracture, said the authors, in contrast to a review in last May's Journal of the American Medical Association. This report suggested a benefit from vitamin D alone for hip or non-spinal fractures.
But Avenell and colleagues, writing in the current issue of The Cochrane Library, say their conclusion showing a benefit only from a combination of vitamin D and calcium is based on a much larger number of patients and on the fact that in some cases, the other study included trials of vitamin D with and without calcium.
The current review found evidence in 38 randomized or quasi-randomized trials that the risk of fractures of the hip and other non-spinal bones was reduced slightly if vitamin D and calcium were given. However, the risk of spinal fractures did not appear to be reduced.
Synthetic vitamin D in drugs such as calcitriol (Rocaltrol) did not appear to have any advantage in preventing bone fracture and may be more likely to cause adverse reactions than natural vitamin D, they added.