A path to sustainable and healthy diets: modeling ovo-lacto-vegetarian food-based dietary guidelines

Introduction The development of healthy and sustainable food-based dietary guidelines (FBDGs) is an essential measure to support the transformation to sustainable and resilient food systems. Shifting to more sustainable and healthy plant-based diets can benefit both human and planetary health, provided these diets are nutritionally adequate, healthy, environmentally friendly, and culturally acceptable. Methods This study aimed to obtain a nutritionally adequate and healthy ovo-lacto-vegetarian diet that reduces greenhouse gas emission (GHGE) and land use (LU) by over 45% in comparison to the average observed diet among Austrian adults, while having the least deviation possible in terms of composition from this average observed diet using mathematical optimization. The results of the optimized diet served as a basis for deriving the ovo-lacto-vegetarian FBDGs. Results The optimized diet met all dietary reference values (DRVs) except for docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and was associated with a potential 41% reduction in disability-adjusted life years (DALYs) compared to the observed diet-related burden of disease in the Austrian population. It resulted in GHGE of 2.5 kg CO 2 –eq (carbon dioxide equivalent), and a LU of 2.9 m 2 /day, corresponding to reductions of 58% and 61%, respectively. The share of energy from animal-based foods decreased from 29 E% (percentage of daily energy intake) in the observed diet to 21 E% in the optimized diet. Plant-based foods provided 65% of total protein in the optimized diet. The derived ovo-lacto-vegetarian FBDGs emphasize vegetables, fruits, grains and legumes, with only small amounts of animal-based foods, and recommend higher intakes of legumes and plant-based meat alternatives to support a shift toward a more sustainable diet. Discussion This study demonstrates that it is possible to model ovo-lacto-vegetarian FBDGs that are healthy, nutritionally adequate and environmentally sustainable, offering a promising approach for future dietary guidelines. National-level dietary modeling should form the basis for the development of healthy and sustainable FBDGs in the future.