A large scale study of nearly 70,000 patients from the U.S. and Europe has found that taking both calcium and vitamin D supplements helps individuals reduce the incidence of bone fractures.

"What is important about this very large study is that goes a long way toward resolving conflicting evidence about the role of vitamin D, either alone or in combination with calcium, in reducing fractures," said study co-author John Robbins, professor of internal medicine at the University of California Davis.

Robbins and an international team of colleagues analyzed the results of seven large clinical trials from around the world to assess the effectiveness of vitamin D alone or with calcium in reducing fractures among people aged 70 years or older. The researchers could not identify any significant effects for people who only took vitamin D supplements.

"This study supports a growing consensus that combined calcium and vitamin D is more effective than vitamin D alone in reducing a variety of fractures," said Robbins. "This combination of supplements benefits both women and men of all ages, which is not something we fully expected to find. We now need to investigate the best dosage, duration and optimal way for people to take it."

Calcium and vitamin D are widely available in nutritional supplement form. Dietary sources that contain both nutrients include fortified dairy products like milk, cheese and yogurt as well as fortified orange juice and soy beverages.