Vitamin D tied to fewer stress fractures in girls

Reuters Health/Chicago Tribune—March 5, 2012

In a new study, girls and young women who got lots of vitamin D through their diet and supplements were half as likely to suffer a stress fracture as those who didn't get much of the vitamin.

Stress fractures are small cracks in the bone that typically affect people who do lots of high-impact exercise, like running or gymnastics. And they're especially concerning in teen girls because bone strength at that age is tied to the risk of osteoporosis and more serious injuries later in life.

Just under four percent of the girls had had a stress fracture, with a much higher risk seen among those who did high-impact exercise for at least an hour a day, according to findings published Monday in the Archives of Pediatrics & Adolescent Medicine.

While there was no link between how much calcium girls and young women got in their diets and their chance of getting injured, those with the greatest daily vitamin D intake were half as likely to have a stress fracture as those who got the least.

Doctors are paying more attention when it comes to vitamin D levels as they relate to fracture risk and healing, according to Dr. Daniel Green, who has studied stress fractures in adolescent athletes at Hospital for Special Surgery in New York.

"Often the kids who are taking a longer time to heal or the kids who didn't heal their fractures predictably, we're finding end up having low vitamin D levels in their blood," said Green, who wasn't involved in the new study.

"Three or four years ago we rarely asked our patients about their vitamin D intake and rarely checked their vitamin D level," he told Reuters Health. "Now, that conversation is happening on a daily basis."

Vitamin D is naturally present in fatty fish, but is also added to dairy products like milk and yogurt. Doctors typically recommend girls and young women take a supplement that includes vitamin D, because it's not always easy to get enough through food.

The Institute of Medicine recommends kids and adults get 600 international units (IU) of vitamin D daily. Girls in the study were getting an average 376 IU per day.

Green recommends 1,000 IU per day to his adolescent patients, and more for those who are very deficient in the vitamin.