title: Serum 25-Hydroxyvitamin D in Early Childhood Is Nonlinearly Associated with Allergy.
abstract: BACKGROUND
  Vitamin D has several immunological functions. Data on the relation of vitamin D status and allergy are controversial.
  
  
  METHODS
  We investigated the association between serum concentrations of 25-hydroxyvitamin D (25-OHD) and allergy in childhood. The study population (n = 819) was part of a randomized, double-blind, placebo-controlled trial where the mothers of offspring with a high risk for allergy received a mixture of probiotics (or placebo) for the last 4 weeks of pregnancy, and the child received this from birth to 6 months. Study subjects were followed for the emergence of sensitization and allergic symptoms for a period of 5 years, with medical examinations at the ages of 3 and 6 months, 2 and 5 years and also in the event of allergic symptoms. Levels of 25-OHD were measured in umbilical cord blood (UCB) samples (n = 724) and serum samples drawn at the age of 2 years (n = 369); the data were categorized into tertiles (T1-T3) and quartiles (Q1-Q4). The relation between 25-OHD levels and sensitization and allergy was analyzed with multivariable logistic regression analysis.
  
  
  RESULTS
  25-OHD levels in T2 in UCB were associated with a higher risk for sensitization by the age of 2 years and allergic disorders by the age of 5 years. In the serum samples, at the age of 2 years, 25-OHD levels in Q3 were associated with a higher risk of sensitization and IgE-mediated allergies by the age of 5 years.
  
  
  CONCLUSIONS
  The 25-OHD levels in early childhood are associated with the emergence of allergy, but the association appears to be nonlinear.
authors.affiliation: Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
authors.forename: Emma Merike
authors.initials: EM
authors.lastname: Savilahti
authors.forename: Outi
authors.initials: O
authors.lastname: Mäkitie
authors.forename: Anna Kaarina
authors.initials: AK
authors.lastname: Kukkonen
authors.forename: Sture
authors.initials: S
authors.lastname: Andersson
authors.forename: Heli
authors.initials: H
authors.lastname: Viljakainen
authors.forename: Erkki
authors.initials: E
authors.lastname: Savilahti
authors.forename: Mikael
authors.initials: M
authors.lastname: Kuitunen
mesh_terms: D000818:Animals; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000097:blood* / Q000175:diagnosis / Q000276:immunology; D007114:Immunization; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016017:Odds Ratio; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; D007073:Immunoglobulin E; C104450:25-hydroxyvitamin D