High vitamin D use linked to fewer stress fractures in females

It helps in absorption of calcium

NEW YORK — Girls and young women who took lots of vitamin D were half as likely to suffer a stress fracture as those who didn’t get much of the vitamin, according to a U. S. study that followed thousands of girls.

Stress fractures are small cracks in the bones that typically affect people who do a lot of high- impact exercise, such as running or gymnastics. They’re especially a concern for teen girls because bone strength at that age is tied to the risk of osteoporosis and more serious injuries later on.

“This study can add to the existing thought that adolescent girls and young women should be particularly cognizant of getting their vitamin D,” said Kendrin Sonneville, from Children’s Hospital Boston, who worked on the study.

Vitamin D is naturally present in fatty fish, but is also added to dairy products such as milk and yogurt. Since it’s not always easy to get enough through food, doctors recommend taking supplements.

Researchers have wondered whether eating a high- calcium diet with lots of dairy products might protect against stress fractures, but in the study it was high levels of vitamin D that were tied to fewer fractures, not calcium.

For the study, published in the Archives of Pediatrics & Adolescent Medicine, the researchers followed close to 7,000 girls who were the daughters of women participating in the long- term Nurses’ Health Study.

Starting when the girls were between nine and 15, the researchers surveyed them every year or so between 1996 and 2001 about their typical eating habits and use of vitamin supplements. From that information, they calculated how much vitamin D each girl got in a typical day.

Then, in 2004, Sonneville’s team asked the girls’ mothers whether their daughter had been diagnosed with a stress fracture from 1997. Just under four per cent of the girls said they had a stress fracture, with a much higher risk seen among those who did high- impact exercise for at least an hour a day.

While there was no link between how much calcium girls and young women received from 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.

Vitamin D is necessary for calcium absorption.

The findings can’t prove the vitamin itself prevents fractures, since it’s possible there were other differences between girls that the researchers couldn’t measure.

But experts said they have found patients who are taking a longer time to heal from stress fractures often have low levels of vitamin D in their blood.

The Institute of Medicine recommends that children and adults get 600 international units of vitamin D daily.