Background Vitamin D is known to have a number of immunological effects and it may play a role in preventing allergic diseases.
Objectives To study the effect of maternal intake of vitamin D during pregnancy on the emergence of asthma, allergic rhinitis (AR), and atopic eczema by the age of 5 years in children with HLA-DQB1-conferred susceptibility for type 1 diabetes.
Methods Children (1669) participating in the population-based birth cohort study were followed for asthma, AR, and atopic eczema assessed by validated questionnaire at 5 years. Maternal diet was assessed by a food-frequency questionnaire.
Results The mean maternal intake of vitamin D was 5.1 (SD 2.6) μg from food and 1.4 (2.6) μg from supplements. Only 32% of the women were taking vitamin D supplements. When adjusted for potential confounders, maternal intake of vitamin D from food was negatively related to risk of asthma [hazard ratio (HR) 0.80; 95% confidence interval (CI) 0.64–0.99] and AR [HR 0.85; 95% CI 0.75–0.97]. Vitamin D supplements alone were not associated with any outcome. Adjustment for maternal intake of other dietary factors did not change the results.
Conclusion Maternal vitamin D intake from foods during pregnancy may be negatively associated with risk of asthma and AR in childhood.