Vitamin D status in professional ballet dancers: winter vs. summer.

OBJECTIVE Serum 25-hydroxyvitamin D is produced by the exposure of the skin to sunlight. Therefore athletes who train indoors, such as dancers, are vulnerable to vitamin D deficiency. The purpose of the study was to evaluate the serum 25-hydroxyvitamin D status in UK professional dancers during periods of reduced and increased sunlight exposure (i.e., winter vs. summer), and to assess the impact on bone metabolism and risk of injury. DESIGN Cohort study. METHODS 19 elite classical ballet dancers (age 26±8.86yr; height 1.66±8.84m; mass 54.3±10.47kg) were monitored over a 6 month period for 25-hydroxyvitamin D, PTH and blood serum bone turnover markers (CTX and PINP) along with injury data. Repeated measure ANOVA and Wilcoxon and Chi-square analyses were used and significance was set at p≤0.05. RESULTS Significant changes were noted between the winter and summer test dates for 25-hydroxyvitamin D (14.9ng/ml vs. 23.9ng/ml; p<0.001), PTH (38.7pg/ml vs. 26.3pg/ml; p<0.001) and PINP (89.9ng/ml vs. 67.6ng/ml; p<0.01). The oral contraceptive had a significant effect on serum 25-hydroxyvitamin D, PTH and CTX. Soft tissue injuries were significantly lower in summer compared to winter period (winter=24, summer=13; p<0.05). CONCLUSIONS Professional ballerinas characterized by a high incidence of low serum 25-hydroxyvitamin D levels which improve marginally in the summer. These dancers also demonstrate a higher injury incidence in the winter. Oral contraception seems to increase serum 25-hydroxyvitamin D levels and has a positive effect on bone metabolism.