title: An association of serum vitamin D concentrations < 40 nmol/L with acute respiratory tract infection in young Finnish men.
abstract: BACKGROUND
  The effects of vitamin D in regulating bone mineralization are well documented. The action of vitamin D as a key link between Toll-like receptor activation and antibacterial responses in innate immunity has recently been shown. The data suggest that differences in the ability of human populations to produce vitamin D may contribute to susceptibility to microbial infection.
  
  
  OBJECTIVE
  We aimed to explore whether an association exists between vitamin D insufficiency and acute respiratory tract infection in young Finnish men.
  
  
  METHODS
  Young Finnish men (n = 800) serving on a military base in Finland were enrolled for this study. Their serum 25-hydroxyvitamin [25(OH)D] concentrations were measured in July 2002. They were followed for 6 mo, and the number of days of absence from duty due to respiratory infection were counted.
  
  
  RESULTS
  The mean (+/- SD) serum 25(OH)D concentrations were 80.2 +/- 29.3 nmol/L (n = 756). Subjects with serum 25(OH)D concentrations < 40 nmol/L (n = 24) had significantly (P = 0.004) more days of absence from duty due to respiratory infection (median: 4; quartile 1-quartile 3: 2-6) than did control subjects (2; 0-4; n = 628; incidence rate ratio 1.63; 95% CI: 1.15, 2.24). We found a significant (P = 0.004) association between serum 25(OH)D concentrations and the amount of physical exercise before induction into military service. We also found significantly (P < 0.001) lower serum 25(OH)D concentrations in subjects who smoked (72.8 +/- 26.6 nmol/L; n = 192) than in control subjects (82.9 +/- 29.7 nmol/L; n = 537).
  
  
  CONCLUSIONS
  Clinical trials of vitamin D supplementation are needed to investigate whether it enhances immunity to microbial infections.
authors.affiliation: Department of Cell Biology and Anatomy, Medical School, University of Tampere, Tampere, Finland. ilkka.laaksi@uta.fi
authors.forename: Ilkka
authors.initials: I
authors.lastname: Laaksi
authors.forename: Juha-Petri
authors.initials: JP
authors.lastname: Ruohola
authors.forename: Pentti
authors.initials: P
authors.lastname: Tuohimaa
authors.forename: Anssi
authors.initials: A
authors.lastname: Auvinen
authors.forename: Riina
authors.initials: R
authors.lastname: Haataja
authors.forename: Harri
authors.initials: H
authors.lastname: Pihlajamäki
authors.forename: Timo
authors.initials: T
authors.lastname: Ylikomi
mesh_terms: D000208:Acute Disease; D000328:Adult; D000704:Analysis of Variance; D004198:Disease Susceptibility; D015444:Exercise / Q000502:physiology; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008889:Military Personnel; D016017:Odds Ratio; D012141:Respiratory Tract Infections / Q000097:blood* / Q000453:epidemiology* / Q000517:prevention & control; D012907:Smoking / Q000097:blood; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood* / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology* / Q000517:prevention & control