Vitamin D and upper respiratory tract infections in young active males exposed to cold environments.

INTRODUCTION AND OBJECTIVE: Performing indoor and outdoor work in cold environments may result in various adverse effects on human health and may lead to increased risk of respiratory infection. The aim of this study was to determine the relation of vitamin D status to secretory immunoglobulin A concentration, leucocyte counts, cytokine concentrations and incidence of upper respiratory tract infection (URTI) episodes in young active men during an autumn-winter period. MATERIAL AND METHODS: The effect of work in a cold microclimate was studied among 23 young active male ice hockey players during a 19-week study period. Blood and saliva samples were collected 7 times during the study period. Incidence of URTI was evaluated using WURSS 21. White blood cell, neutrophil, lymphocyte, monocyte, eosinophil and basophil counts, concentrations of 25(OH)D, C-reactive protein, cortisol, IL-1ra, IL-10, IL-1β and immunoglobulins A, M and G, were determined in the blood. Secretory immunoglobulin A, A1 and A2 and cortisol were analysed in saliva. Spearman's correlations were used to evaluate relationships between initial or final 25(OH)D concentration and URTI incidence, as well as the immune and endocrine markers. Differences in URTI episodes, immune and endocrine parameters between sufficient ( ≥20 ng·ml -1) and deficient (<20 ng ·ml -1) vitamin D status groups were compared with the Mann-Whitney test. RESULTS: There were no statistically significant correlations between mucosal and blood markers or URTI incidence and initial and final 25(OH)D concentrations. Immune, endocrine and URTI variables did not differ between deficient and sufficient vitamin D status groups. CONCLUSIONS: 25(OH)D concentration has no impact on mucosal and systemic immunity, nor on URTI episodes.