Vitamin D might not lower the risk of bone fractures unless it's taken with calcium.
Previous research on vitamin D's effects have been conflicting. Some studies have found supplements reduce the risk of fractures, but others haven't. Researchers in Denmark analyzed seven studies on the question. The studies included a total of 68,517 people whose average age was 70.
The study concluded that vitamin D given alone in doses of 10 to 20 micrograms per day is not effective in fracture prevention. But when calcium and vitamin D were given together, the fracture rates were reduced.
The analysis, however, compared vitamin D with no treatment or vitamin D plus calcium versus no treatment. There was no direct comparison of vitamin D alone and vitamin D plus calcium.
The authors of the new study, published in the British Medical Journal, acknowledge that additional vitamin D studies are needed.