I take care of a lot of adolescent girls, including many who are involved in competitive sports. As participation in organized sports and single sports year round has increased, so have overuse injuries.
One of the most common overuse injuries is a stress fracture, which occurs when stresses on the bone exceed the bone's capacity to withstand and heal from those forces. Stress fractures have been reported to occur in 3.9 percent of adolescent girls, and 90 percent of those fractures occurred in girls who participated in at least 1 hour/day of high impact activity.
During my adolescent visits, I have routinely emphasized the importance of healthy diets, as well as the need for calcium and calcium-rich dairy products. Because adolescence is the most critical period for bone mineral deposition, it has been considered an important window to hopefully prevent osteoporosis later in life.
In a recent study from Harvard University, over 6,700 girls ages 9-15 were followed for 7 years to identify whether calcium, vitamin D, and/or dairy intake was associated with stress fracture. Surprisingly, there was no evidence that calcium and dairy intakes were protective against developing a stress fracture. However, higher vitamin D intake among girls who participated in at least 1hour/day of high-impact activity was predictive of a lower risk of developing a stress fracture.
So, while a balanced diet including dairy products is important for overall health, vitamin D seems to be protective and lowers the risk of a stress fracture. The study did not look at vitamin D intake above 600 IU/day (the current recommended dietary allowance). Further research will be needed to see if even higher amounts of Vitamin D prove to be even more protective.
In the meantime, make sure that your adolescent is getting the recommended daily dose of Vitamin D and keep watching for further studies to determine the mechanism through which Vitamin D may alter stress fracture risk.
Dr. Sue Hubbard is a nationally known pediatrician and co-host of "The Kid's Doctor" radio show. Submit questions at www.kidsdr.com.