Vitamin D status and bone mineral density in female collegiate dancers and cheerleaders

Introduction: An athlete's bone mineral density reflects their cumulative history of energy availability, physical activity, genetic predisposition for bone health, and menstrual status, as well as nutritional, behavioral, and environmental factors. Purpose: To determine if bone mineral density (BMD) and nutritional factors in bone health are different in two groups of female athletes who have comparable body size/weight requirements, but who engage in qualitatively different training regimens. Methods: Participants were female collegiate athletes who were members of the UNLV Dance team (n=10) or Cheer team (n=9), ages 18-22. Participants vitamin D status was assessed by obtaining a finger prick sample of blood (< 1 ml). BMD for full body, spine and dual femur was assessed by dual energy X-ray absorptiometry (DXA). A calcium and vitamin D intake questionnaire was also completed. Results: There was no significant difference between the groups for total body BMD (1.23 g/cm2 dance vs 1.22 g/cm2 cheer, p=0.70), spine BMD (1.39 g/cm2 dance vs 1.36 g/cm2 cheer, p=0.72) or dual femur BMD (1.20 g/cm2 dance vs 1.11 g/cm2, p=0.23). Age matched z- scores for total body BMD were also not significantly different (1.46+/-1.23 dance vs 0.83+/-0.52 cheer, p=0.19). However there was a significant difference between age-matched z-scores of the dance team vs. non-athlete female controls (1.46+/-1.23 dance vs 0.19+/-1.22 control, p=0.033). Serum vitamin D status was found to be insufficient (10-29 ng/mL) in 74% of the athletes (27 +/- 4 ng/mL dance and 25 +/- 8 ng/mL cheer). Daily calcium intake was 504 +/- 723 mg for dance and 531 +/- 236 mg for cheer versus the RDA of 1,000mg/day. Daily vitamin D intake was 256 +/- 335 IU for dance and 228 +/- 145 IU for cheer versus the RDA of 600 IU/day. Conclusion: BMD was not significantly different between the low impact dance team and high impact cheer team. These results suggest that the type of activity (low impact dance vs. high impact cheerleading) was not as important for BMD as participating in 20+ hours a week of physical activity. Although the low levels of calcium and serum vitamin D are of concern, the amount of physical activity in these athletes could have counteracted the negative effects of these nutrient insufficiencies on their bone health.