NEW YORK (Reuters Health) – Older women with higher concentrations of vitamin D in their blood are less likely to sustain hip fractures, according to research published in the Annals of Internal Medicine.

The findings provide additional evidence that taking vitamin D supplements is an easy, low-cost way to prevent hip fractures, which can have devastating consequences for older people, lead author Dr. Jane A. Cauley of the University of Pittsburgh told Reuters Health.

Deficiency in the “sunshine vitamin” is common among seniors, particularly in winter, and there is growing evidence linking a lack of vitamin D to increased hip fracture risk, Cauley and her team report. There are several ways vitamin D may protect against hip fracture, they add, not only by helping to strengthen bone but also by boosting balance and muscle strength, and thus helping to prevent falls.

The researchers examined the relationship between blood levels of vitamin D and hip fracture risk by comparing 400 women who suffered hip fractures and 400 controls, all of whom were participating in the Women’s Health Initiative Observational Study. All were postmenopausal, and none were taking estrogen or other potentially bone-building medications.

The average vitamin D concentration for women who sustained hip fractures was 55.95 nmol/L, compared with 59.60 nmol/L for the controls, a statistically significant difference. Hip fracture risk rose steadily as vitamin D concentrations fell. The women with concentrations of 47.5 nmol/L or lower were 71 percent more likely to have fractured their hips than the women with concentrations of 70.7 nmol/L or higher.

The optimum level of vitamin D is not clear, but having levels below 20 nmol/L is known to increase hip fracture risk, Cauley said in an interview. It’s relatively easy to have your vitamin D levels tested, she added, and insurance should cover it.

While 400 IU is the current recommendation for daily vitamin D intake, she said, experts on the nutrient agree that this is too low, and that 800 IU to 1,000 IU is probably needed. “We don’t really want to recommend sunlight exposure because of the risk of melanoma,” Cauley said. “The supplementation is probably the way to go in terms of increasing your vitamin D intake.”

People should also be sure to take supplements that include vitamin D3, or cholecalciferol, she recommended. D3 is more readily absorbed and biologically potent than vitamin D2, the form often found in multivitamins, according to Cauley.

SOURCE: Annals of Internal Medicine, August 19, 2008.