High reliance on fortified foods when optimizing diets of adolescents in Sweden for adequate vitamin D intake and climate sustainability

The global food system contributes roughly one-third of global greenhouse gas emissions (GHGEs) making shifts towards more sustainable food consumption an imperative. Such diets also need to factor in nutrient requirements and cultural acceptability. Our aim was to simulate dietary changes for adolescents in Sweden to achieve the recommended intake (RI) for vitamin D while factoring in additional nutrients, cultural acceptability and keeping the diet within planetary boundaries for climate change. A baseline diet was estimated from Sweden's national dietary survey Riksmaten Adolescents 2016-17 (n = 3099, ages 11-18 years), which provided food intake via two 24-hour recalls. Intake data were linked to the Swedish Food Agency's food composition database and GHGE estimates from the Research Institutes of Sweden's (RISE) Food Climate Database. Linear programming was used to optimize the baseline diet to meet the RI for vitamin D (10µg/day), reduce GHGEs to ≤ 1.7kg CO₂-equivalents/person/day, and minimize dietary changes from baseline to factor in cultural acceptability. A second optimization included 25 additional nutrients requirements. Both optimized diets met their respective requirements reducing GHGEs by 54% but relied heavily on milk and yoghurt (fortified by law), which provided > 60% of vitamin D intake. Both diets also required major shifts toward plant-based foods and the second optimization demanded a five-fold greater change in diet from baseline compared to first optimization. Results suggest that adolescents in Sweden can achieve RIs for vitamin D and other nutrients while greatly reducing diet-related GHGEs, though cultural acceptability may be a challenge.