This project is based on the Norwegian Mother and Child Cohort Study (MoBa). While limited human evidence is available on the association of childhood atopic diseases with maternal diet during pregnancy and gene methylation in the offspring, new murine st udies from our collaborators at the National Institute of Environmental Health Sciences (NIEHS) in the US have identified effects of high intake of methyl donors during gestation on gene methylation in relation to the development of an allergic asthmatic- type response in the offspring. In this proposal, which includes the first phase of the project, we will investigate if maternal intake of methyl donors in pregnancy affects risk of asthma and atopy at age 3 years. When additional funding is granted, futu re studies based on this project will examine whether mothers with high levels of biomarkers of methyl donor intake give birth to offspring with increased methylation in the genes identified in the mice studies and in additional human atopic disease candi date genes. Further, we will examine whether methylation of these genes is associated with the development of asthma phenotypes. This study will advance knowledge of the mechanisms whereby diet, and other environmental factors, influences gene expression and risk of atopic disease. Analyses of maternal methyl donor status, B-vitamin metabolism and methylation patterns will give great insights in how environmental factors in pregnancy and childhood can influence methylation and DNA regulation. The current study will address associations between childhood respiratory and atopic diseases and maternal b-vitamin status and SNPs in B-vitamin metabolism. Results from this study will form the basis of the project and the future studies.