The World Health Organisation (WHO) and the Food and Agriculture Organisation (FAO)’s global nutrient intake requirements are important as many countries adopt these as part of their national dietary allowances, as well as a foundation to develop food-based dietary guidelines. In 2019, the FAO-WHO initiated an update of their 2004 nutrient intake recommendations for vitamin D, as well as calcium and zinc, prioritizing infants and young children under 4 years of age. This update exercise followed the Risk Assessment Framework, which involved a sequence of independent systematic evidence-based reviews, followed by an appraisal of the evidence around the relationship of serum 25-hydroxyvitamin D (25OHD) and the critical indicator health outcome of nutrient adequacy, so as to derive a population serum 25OHD target, and which, in turn, was used to establish the recommended vitamin D intake for 0 to 4 year olds. This presentation will outline how amongst various potential health outcomes that were considered, minimization of nutritional rickets in young children was selected as the critical indicator health outcome. It will also overview a systematic review of studies involving children below 4 years of age with serum 25OHD levels and radiologically confirmed rickets. This review provided data for study-level and individual participant data-level meta-analyses, the findings of which suggested that a minimum serum 25OHD threshold of around 28 nmol/L. Above this serum 25OHD threshold, the risk of nutritional rickets for the majority of children with an adequate calcium intake would be considered low. The presentation will then overview the novel modelling of the response of serum 25OHD to total vitamin D intake in children below 4 years of age, including consideration of inter-individual variability, which facilitated the derivation of updated vitamin D requirements in young children. These analyses showed that at a vitamin D intake of 10 mg/day, 97.5% of young children would achieve a minimal serum 25OHD threshold of 28 nmol/L. This new estimate of vitamin D requirements for young children infants and can be used by countries across the globe once appropriate local context adjustments, such as contribution to vitamin D status from sun exposure, are made to suit the intended population.