Vitamin D levels and predictors in Swiss elite athletes – recommandation for supplementation

Abstract

Background: Vitamin D concentrations corresponding to 75 nmol/L of 25(OH)D or more have been related to maintained muscle function, growth and regeneration, to optimal bone health and immunology in athletes. The objective of this study was to investigate prevalence and predictors of insufficient 25(OH)D concentrations in athletes and to come up with recommendations for our Swiss athletes. Methods: 603 competitive Swiss athletes were assessed during their annual pre-participation examination. A standardized questionnaire was used to gather information about potential predictors for 25(OH)D concentrations. Results: One in 2 athletes showed insufficient 25(OH)D concentrations. Differences in predicted probability of insufficient 25(OH)D were found for those that were not substituted (56%) vs. those substituted (42%) versus unsubstituted (52%), for those performing indoor (58%) vs. outdoor (43%) sports and during the sun deprived seasons fall (49%), winter (70%) and spring (57%) as compared to summer (17%). An increase in BMI z-scores and age was associated with higher 25(OH)D. Implication: One in two Swiss athletes shows insufficient 25(OH)D concentrations. To prevent potential harmful consequences on athletic performance, muscular, skeletal and immunological health, we recommend a regular substitution in daily, weekly or monthly intervals with a daily equivalent dose of 600–2000 IE Vit D except perhaps in summer. Routine assessments of 25(OH)D concentrations are not necessary.