Association between Maternal Vitamin D Intake and Infant Allergies: The Japan Environment and Children’s Study

Summary Maternal nutrition during pregnancy is one of the factors affecting the health of offspring. There are conflicting findings about the association between maternal vitamin D status and the development of allergic diseases in offspring. The purpose of this study is to evaluate the association between maternal vitamin D intake and the development of allergic diseases in offspring at 1 y of age. From an ongoing nationwide birth cohort study (the Japan Environment and Children’s Study), we obtained information on maternal vitamin D intake, determined by a food frequency questionnaire, and parent-reported physician-diag-nosed allergic diseases in offspring at 1 y of age. From the full dataset of 103,062 pregnan-cies, we analyzed complete data for 82,592 mother–offspring pairs. The prevalence of phy-sician-diagnosed asthma, food allergy, and atopic dermatitis in the children was 2.5%, 6.6%, and 4.3%, respectively. The mean (6 standard deviation) maternal vitamin D intake was 4.764.7 mg/d, which is much lower than the recommended amount in Japan (7 mg/d). After adjustment for various covariates, the odds ratios were significantly higher for asthma in the 2nd quintile and for food allergies in the 3rd and 4th quintiles compared with the 1st quintile. However, there were no clear associations between maternal vitamin D intake and the development of allergic diseases in offspring at 1 y of age, even in a large nation-wide cohort study. Protective effects of vitamin D supplementation remain unclear.