Vitamin D Supplementation and Upper Respiratory Tract Infections in Adolescent Swimmers

Vitamin D Supplementation, Upper Respiratory Tract Infections, Immune and Physical Functions in Adolescent Swimmers

Background: The medical and economic burden of upper respiratory tract infections (URTIs) is extremely high, while prevention and treatment options are limited. Therefore, there is a constant need for new methods in order to significantly decrease such morbidity. Extensive evidence shows that vitamin D is associated with respiratory health, including in the prevention and treatment of URTIs. Competitive swimmers have a high prevalence of URTIs, and can serve as a model for research in this field. The study hypothesis is that vitamin D supplementation to young swimmers with low vitamin D levels will reduce the frequency, length, and severity of URTIs and their accompanying functional impairment, while improving cellular immune function and physical function. Methods: After screening 100 competitive adolescent swimmers to obtain ~60 with low serum levels of vitamin D, this study group will be randomized to receive either vitamin D supplementation (2000 IU/d) or placebo, given in a double blinded fashion for three months. Participants will fill a daily questionnaire regarding frequency, length and severity of URTIs symptoms and functional impairment. Blood will be drawn to evaluate changes in vitamin D status (25(OH)D) and immune function among study participants at the beginning of the study and after supplementation. Physical function on land and in water will also be assessed. Expected results: Increase in serum 25(OH)D levels following supplementation will significantly decrease the frequency, length and severity of URTI's and their functional impairment, while enhancing the cellular immune system function and physical capacity.

URI frequency will be measured in both groups, starting 4 weeks after initiating the suplementation. Analysis will also assess differences by sex or initial vitamin D levels, as well as by immune function changes.

URI duration will be measured in both groups, starting 4 weeks after initiating the suplementation. Analysis will also assess differences by sex or initial vitamin D levels, as well as by immune function changes.

URI severity will be measured in both groups, starting 4 weeks after initiating the suplementation. Analysis will also assess differences by sex or initial vitamin D levels, as well as by immune function changes.

T-cell receptor excision circles (TREC), T cell receptor repertoire, B-cell receptor excision circles (BREC). Comparison will be made with changes in vitamin D levels and with URI characteristics.

absence from school or training, land and swimming fitness tests. Comparison will be made with changes in vitamin D levels.

Inclusion Criteria: members of swimming team training at least 15 hours/week low vitamin D plasma levels (<30 ng/ml) signed consent forms Exclusion Criteria: chronic health conditions taking prescription medications taking diet supplementations

Dubnov-Raz G, Rinat B, Hemila H, Choleva L, Cohen AH, Constantini NW. Vitamin D supplementation and upper respiratory tract infections in adolescent swimmers: a randomized controlled trial. Pediatr Exerc Sci. 2015 Feb;27(1):113-9. doi: 10.1123/pes.2014-0030. Epub 2014 Jul 15.