Vitamin D3 Supplementation on Immune Functions and Upper Respiratory Track Infection in Male Taekwondo Athletes

Abstract

Vitamin D plays an important role for immune functions. Insufficient serum 25(OH)D concentration during winter season may be associated with increased risk of upper respiratory tract infection (URTI) in athletes. PURPOSE: This study was aimed to determine the effects of vitamin D3 supplementation on immune functions and URTI in male taekwondo athletes. METHODS: Twenty-five male taekwondo (TKD) athletes, aged 19-22 years with vitamin D deficiency (25(OH)D; 12.3±2.78 ng/ml), participated in this study. They were randomly assigned to receive 5,000 IU/day of vitamin D3 capsule (N=13) or placebo (N=12) during 4 weeks of winter training. Blood samples were collected two times (pre- and post-tests) to analyze serum 25(OH)D concentration. Saliva samples were collected three times (1st, 2nd, and 4th week) to analyze the salivary immunoglobulin A (SIgA) and lactoferrin concentrations. URTI symptoms were reported daily during 4 weeks of training. Repeated measures ANOVAs were performed and significant level was set at p<.05. RESULTS: The serum 25(OH)D concentration increased by 255.6% in supplementation group, but this level did not change in placebo group (F=247.50, p<.001). SIgA (F=23.00, p<.001) significantly increased in both groups during the study period, but salivary lactoferrin level (F=5.79, p=.011) increased only in placebo group at the 2nd week of training. URTI symptoms significantly decreased only in supplementation group (F=5.456, p=.005) throughout the study. CONCLUSIONS: The present study found that high dose of vitamin D3 supplementation (5,000 IU/day) increased the serum 25(OH)D concentration to sufficient level (40.1±6.79 ng/ml), and decreased URTI symptoms during winter training. Our findings suggest that vitamin D3 supplementation during winter training may provide potential benefits for preventing URTI in male taekwondo athletes with vitamin D deficient.