Vitamin D status and musculoskeletal health in adolescent male ballet dancers a pilot study

Adequate vitamin D levels during growth are critical to ensuring optimal bone development. Vitamin D synthesis requires sun exposure; thus, athletes engaged in indoor activities such as ballet dancing may be at relatively high risk of vitamin D insufficiency. The objective of this study was to investigate the prevalence of low vitamin D levels in young male ballet dancers and its impact on musculoskeletal health. Eighteen male ballet dancers, aged 10 to 19 years and training for at least 6 hours per week, were recruited from the Australian Ballet School, Melbourne, Australia. Serum 25( OH )D and intact PTH were measured in winter ( July ) from a non-fasting blood sample. Pubertal stage was determined using self- assessed Tanner criteria. Body composition and areal bone mineral density ( aBMD ) at the whole body and lumbar spine were measured using dual-energy x-ray absorptiometry ( DXA ). Injury history and physical activity levels were assessed by questionnaire. Blood samples were obtained from 16 participants. Serum 25( OH )D levels ranged from 20.8 to 94.3 nmol/L, with a group mean of 50.5 nmol/L. Two participants ( 12.5% ) showed vitamin D deficiency [serum 25( OH )D level < 25 nmol/L], seven dancers ( 44% ) had vitamin D insufficiency ( 25 to 50 nmol/L ), and the remaining seven dancers ( 44% ) had normal levels ( > 50 nmol/L ). No relationship was found between vitamin D status, PTH levels, body composition, and aBMD. The most commonly reported injuries were muscle tears and back pain. The average number of injuries reported by each dancer was 1.9 ± 0.4 ( range: 0 to 5 ). There was no difference in the frequency of reported injuries between subjects with vitamin D deficiency or insufficiency ( 2.1 ± 0.6 injuries ) and those with normal vitamin D levels ( 1.4 ± 0.6 injuries ). This pilot study showed that more than half of highly-trained young male ballet dancers presented with low levels of vitamin D in winter. Further investigations in larger samples of adolescent athletes are needed to determine if this could negatively impact bone growth and place them at higher risk for musculoskeletal injuries.