Vitamin D₃ Supplementation Reduces the Symptoms of Upper Respiratory Tract Infection during Winter Training in Vitamin D-Insufficient Taekwondo Athletes: A Randomized Controlled Trial

Int J Environ Res Public Health. 2018 Sep 14;15(9):2003. doi: 10.3390/ijerph15092003.


Vitamin D insufficiency may be associated with increased risk of upper respiratory tract infection (URTI) in athletes. This study examined the effects of vitamin D₃ supplementation on salivary immune functions and symptoms of URTI in vitamin D-insufficient taekwondo athletes. Twenty-five male taekwondo athletes, aged 19⁻22 years with vitamin D insufficiency [serum 25-hydroxyvitamin-D concentrations (25(OH)D, 31.3 ± 1.39 nmol/L)], participated in this study. They were randomized to receive 5000 IU/day of vitamin D₃ (n = 13) or placebo capsule (n = 12) during 4 weeks of winter training. Blood samples were collected two times (pre- and post-tests) for analyzing serum 25(OH)D concentration while salivary samples were obtained three times (pre-, mid-, and post-tests) for secretory immunoglobulin A (SIgA) and lactoferrin analyses. The symptoms of URTI were reported daily during the intervention. Serum 25(OH)D concentration significantly increased by 255.6% in the vitamin D group, whereas in the placebo group it did not change (p < 0.001). While the significant increase in SIgA was observed in both groups (p < 0.001), elevated salivary lactoferrin level in response to winter training was found only in the placebo group (p = 0.011). The change in serum 25(OH)D concentration was negatively associated with total URTI symptoms (r = -0.435, p = 0.015). Vitamin D₃ supplementation may be effective in reducing the symptoms of URTI during winter training in vitamin D-insufficient taekwondo athletes.

Keywords: high-intensity training; respiratory immune function; secretory immunoglobulin; vitamin D.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Athletes
  • Body Composition
  • Cholecalciferol / therapeutic use*
  • Humans
  • Lactoferrin / analysis
  • Male
  • Martial Arts / physiology*
  • Respiratory Tract Infections / prevention & control*
  • Saliva / chemistry
  • Saliva / immunology
  • Seasons
  • Vitamin D / analogs & derivatives
  • Vitamin D / blood
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / drug therapy*
  • Vitamins / therapeutic use
  • Young Adult


  • LTF protein, human
  • Vitamins
  • Vitamin D
  • Cholecalciferol
  • 25-hydroxyvitamin D
  • Lactoferrin