![]() We calculated body mass index (BMI) from self-reported weight and height information. Participants also reported calcium supplement and multivitamin use, physical activity, menstrual status, weight, and height annually from 1996 through 2001. Nutrient intakes were computed by multiplying the frequency of consumption of each unit of food and the nutrient content of the specified portions based on the nutrient values in foods obtained from US Department of Agriculture sources and food manufacturers and includes calcium or vitamin D in foods routinely fortified with these nutrients 24. Briefly, participants were asked how frequently they used a typical portion size of specified foods on average during the past year. The development, reproducibility, and validation of the YAQ has been previously described 22, 23. The YAQ is a self-administered, semi-quantitative, food frequency questionnaire that assesses intake over the past year using portion sizes for foods that are appropriate for each age as determined from analyses of national nutrition data 22, 23. The aim of the current study was to identify dietary factors that are prospectively associated with risk of stress fractures among female adolescents and, in particular, those who are at highest risk for stress fractures.ĭietary intake, including intake of dairy foods and soda, was assessed annually from 1996 through 1999 and again in 2001 using the previously validated Youth/Adolescent Questionnaire (YAQ) 22, 23. As such, prospective studies are needed to identify other modifiable risk factors for stress fractures among this population. However, few studies have identified modifiable risk factors for stress fractures among female adolescents, other than participation in high-impact sports 4, 17. Stress fractures are a source of significant morbidity among female athletes during adolescence 17. ![]() ![]() More research is needed to explore whether protective dietary factors could mitigate the risk of stress fractures among adolescents who regularly engage in high-impact activities. The combined effects of diet and exercise on bone health are still unknown. Despite known benefits of physical activity on bone mineral content 19, there is a threshold over which the risk of stress fracture increases significantly among adolescent girls 17. Physical activity is the primary modifiable stimulus for increased bone growth and development in adolescents 5 and weight-bearing activity during childhood and adolescence seems to be a more important factor for peak bone mass than dietary intake 18. Because bone mineral is accrued over time, however, the contribution of long-term dietary exposure on stress fracture risk cannot be examined in cross-sectional studies or studies of short duration. In a cross-sectional analysis of adolescent girls, dairy, calcium, and vitamin D intake were all unrelated to stress fractures after controlling for age 17. ![]() The relationship between dietary intake during adolescence and short-term consequences of low bone mineral content, however, is understudied. Further, while vitamin D deficiency is relatively common among adolescents 7, 8, data are lacking on the role of vitamin D intake, whether sufficient or in excess of recommended intake 9, on bone health 10, 11.Īdolescence is the most critical period for bone mineral accrual 12- 16 and therefore, is considered an important window for the prevention of long-term consequences of low bone mineral content, such as postmenopausal osteoporosis. Although calcium and calcium-rich dairy products are routinely encouraged for optimal bone health, the evidence for this recommendation has been challenged 5, 6. Nutritional intake, particularly calcium, which is needed for bone mineralization, and vitamin D, which is needed for maintaining calcium homeostasis and bone remodeling, have been suggested as protective against stress fractures 3. The risk of stress fracture is influenced by extrinsic (training regimen, type of sport), intrinsic (gender, race/ethnicity), biomechanical, anatomic, and hormonal factors 3. We have previously reported that nearly 4% of the adolescent and young adult girls in our cohort developed a stress fracture during 7 years of follow-up 4. Stress fractures, which occur when stresses on bone exceed the bone’s capacity to withstand and heal from those forces, are a particularly common type of injury seen in both competitive and recreational athletes 3. As participation in organized sports and athletic specialization among children and adolescents has increased, so too has the recognition of overuse injuries 1, 2.
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