Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals, published an article today showing that vitamin D intake can lower stress fracture risk in girls, especially in regards to injuries caused by high impact style activities.
Stress fractures are a common injury, often related to sports or physical activity. Essentially, the damage occurs when the bone is not able to withstand the pressure and force it is put under. They can also develop over time from repeated impact that might not initially cause any noticeable injury, but after multiple stress episodes become something of a problem to the bone structure.
Whilst it is generally noted that high calcium diets mainly from dairy products are good for bone health and strength, the authors, Kendrin Rc Sc.D., R.D., of Children's Hospital Boston, and colleagues mention in their background study that this assertion does not necessarily hold true.
The scientists looked at more than 6,100 pre-adolescent and adolescent girls (age 9 to 15 at baseline) who were a part of the Growing Up Today Study. Over seven years of follow up nearly four percent of the girls were seen to develop stress fractures, and dairy and calcium intake was not found to be a related cause. Conversely though, vitamin D appears to have been particularly important in maintaining healthy bones, able to withstand high impact events, particularly in those girls involved in an hour or more per day of high stress activity.
The authors noted that :
"In contrast, there was no evidence that calcium and dairy intakes were protective against developing a stress fracture or that soda intake was predictive of an increased risk of stress fracture or confounded the association between dairy, calcium or vitamin D intakes and fracture risk."
The authors also note that in a stratified analysis, high calcium intake was associated with a greater risk of developing a stress fracture, although they suggest that "unexpected finding" warrants more study. The authors conclude that their findings support the Institute of Medicine's recent increase in the recommended dietary allowance for vitamin D for adolescents from 400 IU/d to 600 IU/d.
Obviously, further studies are needed, especially in regards to showing that boys have the same result, but considering the growing number of children with lactose intolerance, problems and the possible misnomer about dairy products that has been uncovered, Sonneville et. al have certainly come up with some useful and enlightening information.
Written by Rupert Shepherd