AND MARJO-RIITTA JÄRVELINb,g

ABSTRACT: Allergen-induced secretion of Th2-type cytokines and IgE produc-tion have recently been reported to be increased in mice treated with 1,25(OH)2D, the active form of vitamin D. Our objective was to investigate whether vitamin D supplementation in infancy is associated with the risk of atopy, allergic rhinitis, and asthma. The Northern Finland Birth Cohort con-sists of all individuals in the two most northern provinces of Finland who were due to be born in 1966. Data on vitamin D supplementation during the first year of life was obtained in 1967. Current asthma and allergic rhinitis were re-ported at age 31 years (n = 7,648), and atopy determined by skin-prick test in a sub-sample still living in northern Finland or the Helsinki area (n = 5,007). The prevalence of atopy and allergic rhinitis at age 31 years was higher in par-ticipants who had received vitamin D supplementation regularly during the first year compared to others (OR 1.46, 95%CI 1.4–2.0, and OR 1.66, 95%CI 1.1–1.6, respectively). A similar association was observed for asthma (OR 1.35, 95%CI 0.99–1.8). These associations persisted after adjustment for a wid