High proportion of young children are vitamin D sufficient after expansion of Sweden’s mandatory fortification but dairy products also contribute to a high climate impact

Sweden expanded its mandatory vitamin D fortification program in 2018 addressing high rates of insufficient vitamin D status and low intake. This study aimed to assess vitamin D status among young children post-expansion, evaluate its determinants, and identify main vitamin D sources and their climate impact. Dietary intake among 18-month-olds (18mo, n = 1074) and 4-year-olds (4yo, n = 746) were obtained from the Swedish national survey Riksmaten Young Children 2021-24 based on two non-consecutive 24-hour food records. Intake of vitamin D from drops (µg/d) was also recorded. Individual vitamin D intakes were adjusted using the Multiple Source Method to reflect habitual intake. Blood concentrations of 25-hydroxyvitamin D (25OHD) were provided for a subset (18mo, n = 281; 4yo, n = 270). Climate impact was expressed as greenhouse gas emissions (GHGEs) in carbon dioxide equivalents (CO₂ eq), using life cycle assessment data from the Research Institutes of Sweden. Associations between 25OHD and plausible determinants were analyzed with linear regression. 16% of 18mo and 61% of 4yo had total vitamin D intakes (including diet and drops) below the average requirement, 7.5 µg/d. None were deficient (25OHD < 30 nmol/l), and 7% of 18mo and 4% of 4yo were insufficient (< 50 nmol/l). 25OHD was positively associated with dietary vitamin D intake and vitamin D from drops, and inversely associated with blood sampling during winter and parents’ birth country (≥ 1 parent born outside Nordics). Main vitamin D sources for 18mo were vitamin D drops and fortified foods: dairy, porridge and cereal drinks; and for 4yo, fortified dairy and fat spreads. Dairy was a large contributor to diet-related GHGEs (18mo: 10%, 4yo: 16%), whereas fortified fat spreads and plant-based dairy alternatives were effective sources of vitamin D, providing the highest vitamin D concentrations per kg CO₂ eq. A high proportion of young children in Sweden are vitamin D sufficient, with dietary vitamin D intake, vitamin D drops, and blood sampling season being major determinants. Fortified dairy is an important dietary source of vitamin D, but a shift to fortified plant-based alternatives would reduce diet-related climate impact and should be explored in future research.