High dose Vitamin D linked to high rate of fractures and falls

By Dr. Ananya Mandal, MDMay 12 2010

Many women have been regularly taking vitamin D supplements in the hope that it is good for their bones. However a new study has shown that high doses of this vitamin can actually increase the number of falls and fractures in older women.

Geoff Nicholson, of Barwon Health and the University of Melbourne in Geelong, and colleagues have been studying the effect of a single annual high-dose of oral vitamin D on older women for the past six years. “We expected to find a reduction in falls and fractures but we found exactly the opposite,” says Professor Nicholson. These findings appear today in the Journal of the American Medical Association (JAMA).

Vitamin D is essential for healthy bones as it aids in the absorption of calcium. It strengthens muscles and joints also to an extent. Professor Nicholson says that little exposure could give us all the Vitamin D we need. However with the fear of skin cancers due to sun exposure on the rise Vitamin D levels have fallen short in most people. “A good proportion of the population, particularly women who are older, have lower vitamin D levels than are considered healthy,” he said. This can lead to brittle bones in a condition called osteoporosis and weak muscles. He added that a review of past studies have shown that vitamin D supplements may be beneficial or may be ineffective. “These things may work. Some studies show they do. Some show they don't. But compliance is a big problem,” says Nicholson.

For this study the Australian researchers have used a high-dose strategy in 2,256 women aged 70 years or older, considered to be at high risk of fracture. The women were given 500,000 international units of cholecalciferol (a form of vitamin D), or placebo, orally once a year for three to five years. The results showed that during the trial there were 5,404 falls, with women in the high-dose vitamin D group having 15% more falls than the placebo group. The vitamin D group had 171 fractures versus 135 in the placebo group, with 26% more fractures for participants in the vitamin D group. They also had a 31% higher incidence of falls in the first three months after taking the vitamin.

Professor Nicholson warns that the actual figures might look small but the risk may be large. “The absolute increase in risk is quite small…[But] if you did it in every woman in Western societies over 70 you're talking about many many fractures.” This phenomenon according to him is still unexplained. “It's very complicated and at this stage we're not in a position to explain it,” he said.

The authors write, “Among older community-dwelling women, annual oral administration of high-dose cholecalciferol resulted in an increased risk of falls and fractures…Our study used the largest total annual dose of vitamin D (500 000 IU) reported in any large randomized controlled trial, raising the possibility that the adverse outcome is dose-related.”

This study was funded by the National Health and Medical Research Council.

Expert speak

Vicki Kotsirilos a spokesperson for the Royal Australian College of General Practitioners (RACGP) applauds the researchers saying, it is a well conducted study. “The College position does not support the use of very high doses of vitamin D for the prevention of falls and fractures in elderly women,” added Dr. Kotsirilos. She emphasized on the need for healthy diet, exercise and getting adequate sunlight in osteoporosis prevention.

In an editorial of the same issue Bess Dawson-Hughes, MD, and Susan S. Harris, DSc, from Tufts University in Boston, Massachusetts, also mentions the need for a better understanding of Vitamin D metabolism and physiology to help understand the underlying mechanism in these findings. “It may also be necessary to reevaluate the risks and benefits of the current clinical practice of providing high loading doses of cholecalciferol to patients who are vitamin D deficient. In the meantime, it is important to reiterate that although vitamin D insufficiency is widespread, it can be safely corrected with a variety of existing supplement types and regimens and it should continue to be identified and treated in clinical practice,” they write.