There is a need for a shift towards healthy and more plant-based diets to address global health and environmental challenges. Well-planned plant-based diets (i.e., vegan, lacto-ovo-vegetarian, pescatarian) can be nutritionally adequate and reduce environmental impact. However, if the diet is not well-planned, there is a risk of inadequate intakes of some essential nutrients. Few studies have assessed the nutritional consequences of consuming plant-based diets of differing strictness among youth and there is a need for new studies in the present era of plant-based diets. The overarching aim of this doctoral thesis is to assess nutritional consequences of consuming plant-based diets of differing strictness in a youth population in Sweden, and to investigate if their intakes are in line with dietary recommendations. To achieve this, a cross-sectional study was conducted in Gothenburg, Sweden, and dietary intake, nutritional status, and food literacy competencies were assessed and compared between youth who adhered to vegan, lacto-ovo vegetarian, pescatarian or omnivorous diets. The final study sample consisted of 235 youth aged 16-24 years (78% female). The results showed that healthy youth consuming well-planned plant-based diets do not, per se, have a nutritionally adverse intake compared with omnivores. In the diet of vegans, fortified plant-based foods (e.g., plant-based dairy alternatives) were main sources of several essential micronutrients (vitamin D, B2, B12, and calcium), and 77% reported using dietary supplements. Nevertheless, nutritional challenges were observed across all dietary groups; some challenges were specific to vegan and lacto-ovo-vegetarian diets, some were associated with increasing consumption of animal-sourced food groups, and some were shared across the four groups. This indicates that dietary improvements are needed regardless of plant-based or omnivorous diet. Biomarker data supported several of the findings from the dietary intake data. Across the four dietary groups, youth demonstrated a moderate level of general nutrition knowledge. Findings from the present doctoral thesis suggest that more specific dietary guidelines are required on the types and quantities of plant-based foods needed to replace animal-sourced foods and achieve nutritionally adequate plant-based diets through foods only. In addition, youth regardless of dietary practice may need more food-related education to strengthen their food literacy competencies.
