Vitamin D deficiency has significant implications for human health and impacts on healthy growth and development and successful aging. Fundamental knowledge gaps are barriers to implementing a safe and effective public health strategy to prevent vitamin D deficiency and optimize status. ODIN will provide the evidence to prevent vitamin D deficiency in Europe and improve nutrition and public health through food. By establishing an internationally standardized analytical platform for 25OHD, ODIN will measure the distribution of circulating 25OHD and describe the prevalence of vitamin D deficiency in Europe. Using available biobanks and databases from National nutrition surveys ODIN will delineate the relative contributions of sun and dietary sources of vitamin D to circulating 25OHD. In support of planned EFSA revisions of vitamin D recommendations, ODIN will carry out three RCT in pregnant women, children and teenagers and a fourth RCT in ethnic immigrant groups to provide experimental data to specify vitamin D intake requirements. Using dietary modeling, innovative food-based solutions to increase vitamin D in the food supply through a combination of bio-fortification of meats, fish, eggs, mushrooms and yeast will be developed and ODIN will test the efficacy and safety of these products in food-based RCT varying in scale from small product-specific trials to a large total diet study in vulnerable indigenous and immigrant sub-groups. ODIN has assembled the largest critical mass of prospective adult, pregnancy and birth cohort studies to date and will conduct meta-analyses and individual subject-level meta-regression analyses to integrate standardized data on vitamin D status, a priori defined clinical endpoints and genotype to examine relationships between vitamin D and human health, including beneficial and adverse effects, on perinatal outcomes, bone growth and body composition and allergic disease in children and cardiovascular disease and mortality in adults.