A Harvard study suggests that higher levels of vitamin D protect against hip fractures By CHRISTINE GORMAN. TIME Magazine (online)
Does taking extra vitamin D decrease your risk of breaking a hip? Over the past ten years medical researchers have published several clinical trials that tried to determine whether vitamin D could protect middle-aged and elderly folks against hip fractures. But the results have been mixed. Some studies found a modest benefit from vitamin D supplementation while others didn't. In addition, most of the studies didn't have that many participants so the conclusions weren't always something you'd want to stake your life on. What do scientists do when several seemingly well-conducted studies don't agree with each other? They perform what's called a meta-analysis in which they pool the data from all the best studies they can find.
After a group of researchers at Harvard and the Brigham and Women's Hospital in Boston conducted just such a meta-analysis, they concluded that vitamin D offers some protection against broken hips and other bones in the elderly but only when folks took between 700 international units (IU) and 800 IU per day. Taking just 400 IU a day—what current U.S. guidelines suggest for men and women between the age of 51 and 70—was not enough. That result may explain why previous studies couldn't agree on the benefits of vitamin D. Some studies looked at a lower amount of vitamin D and others looked at a higher amount. Interestingly, the benefit from the higher dose of vitamin D started showing up after just three months.
There are still plenty of unanswered questions. Since most of the studies in the meta-analysis also included extra calcium, it was impossible to conclude whether the benefit came solely from the vitamin D or from the combination of vitamin D and calcium. Also, because vitamin D is soluble in fat (and can therefore build up to toxic levels in the body), no one should take more than 800 IU a day, except under doctor's orders. The results can be found in the May 11, 2005 issue of the Journal of the American Medical Association. Source: TIME magazine (online)