Transitioning to Healthy Diets Within Planetary Boundaries: Optimized Dietary Scenarios Based on Current Eating Patterns in the Netherlands

Objectives: Present dietary patterns do not align with established nutritional recommendations and surpass the environmental limits set for a sustainable food system. In this study, we aimed to identify diets among Dutch adults that satisfy nutritional requirements and are within planetary boundaries, while minimizing changes from the current diet. Methods: Starting from the habitual diet of Dutch men and women (aged 18-50y) derived from the latest Dutch National Food Consumption Survey, mathematical optimization was used to model diet scenarios with minimized departure from habitual intake. The environmental impacts of representative Dutch foods were adjusted to align with the scope of the planetary boundaries as defined by the EAT-Lancet Commission and to incorporate forecasted improvements in 2030 and 2050. Constraints were applied on nutrients and environmental impacts up to food production (greenhouse gas emissions, blue water use, cropland use, phosphorus application and surplus nitrogen). Furthermore, an upper constraint was established on biodiversity loss (or damage to ecosystems as defined by ReCiPe 2016). Four scenarios were considered in which we modelled different eating patterns, i.e., food-based dietary guidelines, flexitarian, vegetarian and vegan, relaxing constraints where needed to get solutions. Results: Staying within the planetary boundaries and meeting nutritional guidelines require a shift in protein source from 60% animal to 60-70% plant-based. The needed changes in intake point towards reductions in meat, fats/oils, and cakes/biscuits and increase in vegetables, fruits, legumes and nuts. While the vegetarian and vegan diets resulted in the largest reductions in environmental impacts except blue water use, they did not meet all nutritional requirements given the set of food products (docosahexaenoic acid low in both vegetarian and vegan diets, and vitamins B2 and B12 and iron in vegan diet). Conclusions: Healthy diets within planetary boundaries based on Dutch eating patterns require a substantial change in protein source. Vegetarian and vegan diets require alternative food products to fill the nutritional gaps while staying within planetary boundaries. These results contribute to the development of future environmentally sustainable dietary guidelines for the Netherlands. Funding Sources: Wereld Natuur Fonds (WWF-NL).