Association of the 25(OH) vitamin D status with upper respiratory tract infections morbidity in water sports elite athletes.

Background: The aim of this study is to determine seasonal changes of total serum 25(OH) vitamin D (VD) concentration and its influence on upper respiratory tract infection (URTI) morbidity among water sports elite athletes.

Methods: The study was planned as a prospective, non-interventional, observational study. Study participants included 40 elite athletes and 30 control individuals.