title: Vitamin D supplementation improves well-being in patients with frequent respiratory tract infections: a post hoc analysis of a randomized, placebo-controlled trial.
abstract: BACKGROUND
  The aim of this study was to test the hypothesis that vitamin D supplementation improves well-being in patients with frequent respiratory tract infections (RTIs). We performed a post hoc analysis of a randomized, placebo-controlled and double-blind study in which patients with frequent RTIs were randomized to placebo or vitamin D (4000 IE/day for 1 year, n = 124). At the last visit of the study, patients were asked to perform a general assessment of their well-being during the study.
  
  
  RESULTS
  The majority of patients, both placebo- and vitamin D treated, stated that they had felt 'better' during the study; 52% in the placebo group and 70% in the vitamin D group, relative risk 1.3 (95% CI 1.0-1.8; p = 0.06, Fisher's exact test). Statement of better well-being was associated with an increase in 25-hydroxyvitamin D (25-OHD) levels (p < 0.001). In contrast, worse well-being was associated with unchanged 25-OHD levels. Notably, a 25-OHD level above 100 nmol/L at the study end was associated with a higher chance of having a better well-being (p < 0.01). Four patients on anti-depressive treatment could terminate their antidepressant medication during the study. These patients had a significant increase in 25-OHD levels from low levels at study-start.
  
  
  CONCLUSIONS
  Vitamin D supplementation to patients with frequent RTIs might be beneficial, not only for infections, but also for their general well-being. However, given the post hoc design of this study, these findings need to be confirmed in additional clinical trials before firm conclusions can be drawn.
  
  
  BACKGROUND
  http://www.clinicaltrials.gov (NCT01131858), registered March 22, 2010.
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86, Stockholm, Sweden. peter.bergman@ki.se.
authors.forename: Peter
authors.initials: P
authors.lastname: Bergman
authors.affiliation: Division of Clincal Immunology, Karolinska Institutet, Karolinska University Hospital Huddinge, 141 86, Stockholm, Sweden. anna-carin.norlin@karolinska.se.
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Norlin
authors.affiliation: Infectious Disease Clinic, Karolinska University Hospital, 141 86, Stockholm, Sweden. susanne.hansen@karolinska.se.
authors.forename: Susanne
authors.initials: S
authors.lastname: Hansen
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Huddinge, 141 86, Stockholm, Sweden. linda.bjorkhem-bergman@ki.se.
authors.forename: Linda
authors.initials: L
authors.lastname: Björkhem-Bergman
mesh_terms: D000928:Antidepressive Agents / Q000627:therapeutic use; D019587:Dietary Supplements; D006801:Humans; D012141:Respiratory Tract Infections / Q000188:drug therapy*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D000928:Antidepressive Agents; D014807:Vitamin D; C104450:25-hydroxyvitamin D