Methods: The study 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 mothers of offspring with high risk for allergy received for the last 4 weeks of pregnancy a mixture of probiotics, or placebo, and after birth, the child received the same for 6 months. Study subjects were followed for the emergence of sensitization and allergic symptoms for 5 years, with medical examinations at the ages of 3 and 6 months, 2 and 5 years, and in the case of allergic symptoms. Levels of 25-OHD were measured in umbilical cord blood samples (n=724) and serum samples drawn at the age of 2 years (n=369); the data were categorized in tertiles and quartiles. The relation between 25-OHD levels and sensitization and allergy were analyzed with multivariable logistic regression analysis.
Results: 25-OHD levels in the second tertile in umbilical cord blood were associated with higher risk for sensitization by the age of 2 years and allergic disorder by the age of 5 years. In serum samples at the age of 2 years, the third quartile of 25-OHD levels was associated with higher risk of sensitization and IgE-mediated allergies by the age of 5 years.
Conclusions: The 25-OHD levels in early childhood associate with the emergence of allergy but the association appears to be non-linear.