Vitamin D Supplementation and Upper Respiratory Tract Infections in Adolescent Swimmers

Study Overview
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Brief Summary
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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.

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

Conditions
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Upper Respiratory Tract Infections

Intervention / Treatment
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* Dietary Supplement: vitamin D
* Dietary Supplement: placebo


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 12 Years
Maximum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: vit D<br> | Dietary Supplement: vitamin D<br>* 2000 IU/day of vitamin D3 as a once-daily dose<br>|
| Placebo Comparator: placebo<br> | Dietary Supplement: placebo<br>* sweetened water<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| URI frequency | 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. | 3 months | 
| URI duration | 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. | 3 months | 
| UTI severity | 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. | 3 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| plasma vitamin D levels |  | 3 months | 
| immune system function | 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. | 3 months | 
| physical function | absence from school or training, land and swimming fitness tests. Comparison will be made with changes in vitamin D levels. | 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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infections, immune system, vitamin D, sport, children