Reuters Health—July 5, 2012
A new analysis of nearly a dozen studies testing vitamin D in older individuals has concluded that it takes a daily dose of at least 800 international units (IU) to consistently prevent broken bones.
A dose that high was found to reduce the risk of hip fracture by 30 percent and other breaks by 14 percent. Lower doses didn't have any effect.
The report, published in the New England Journal of Medicine, also suggests that too much calcium -- perhaps more than 1,000 milligrams (mg) per day -- can weaken the benefit.
The Institute of Medicine recommends that most adults get 1,000 to 1,200 mg of calcium per day and 600 to 800 IU of vitamin D. It sets a recommended upper limit at 2,000 mg of calcium and 4,000 IU of vitamin D.
Dr. Richard Bockman, a hormone expert at Hospital for Special Surgery in New York, said the findings are an important counterbalance to last month's widely-reported recommendation by the U.S. Preventive Services Task Force.
The government-backed task force advised against taking doses of less than 400 IU of vitamin D with 1,000 mg of calcium and concluded the evidence was unclear for higher doses.
Bockman said the best trial is a 2003 study, known as the Trivedi trial, in which volunteers received an average of 800 IU per day as a single 100,000 IU dose every four months.
"It clearly showed a reduction in fracture risk in people who were getting vitamin D," he said.
This story originally appeared at reuters.com.