Feasible solutions for sustainable diets with adequate protein intake: modelling diets for the Netherlands and Europe

The global food system faces significant challenges, including the need to provide healthy diets to a growing population while protecting the planet. Sustainable diets, as defined by the World Health Organization and the Food and Agriculture Organization, are good for health, have low environmental impact; are accessible, affordable, safe, fair, and fit cultural preferences. These diets usually mean eating more plant-based and less animal-based foods. However, as plant-based foods often contain less protein, and of lower quality, we need to carefully monitor whether sustainable diets provide enough. Besides, a diet should fit cultural habits of a specific population to be feasible. Therefore, this thesis aims to propose feasible solutions for sustainable Dutch diets, and to assess the amount of protein of these and European diets. Part I: Protein quality and adequacy of current European and future Dutch diets. A new score, the Protein Adequacy and Quality Score (PAQS), was developed to assess protein adequacy as the ratio of daily utilizable protein intake to requirement. Utilizable protein intake is the part of consumed protein that can be used for body protein synthesis, i.e. utilizable protein is total protein intake corrected for its digestibility and amino acid composition. Across 25 European countries, almost everyone was found to consume enough utilizable protein, but the diet of some women in Germany might need more attention. Besides, in realistic scenarios, Dutch diets could lower greenhouse gas emissions by 12–16% without compromising protein adequacy and nutritional value. Part II: Feasible solutions for sustainable Dutch diets : Currently, some Dutch adults consume a low-meat diet, which has lower greenhouse gas emissions and is healthier than the average Dutch diet. However, blue water consumption of this diet was higher than current average diets. As this low meat diet is accepted by at least part of the population, it might be used as an example by peers to improve the sustainability of their diet. It was also found that Dutch adults replace their meat by fish, nuts, and cheese, or they ate increased amounts of sweets and snacks instead of meat. These examples are considered acceptable alternatives for meat when trying to eat more sustainably. Including algae in Dutch diets could add some health and environmental benefits, but considerable dietary changes in current consumption patterns with conventional foods could achieve similar results. Changes in dietary intake should coincide with changes in the rest of the food system. Diet optimization models (SHARP) and environmental food system optimization models (CiFoS) can be used when developing policies to move to more sustainable diets. Conclusion: This thesis shows that current European and improved Dutch diets provide enough utilizable protein. Besides, feasible solutions for sustainable Dutch diets include small steps toward a more plant-based diet. Larger changes could offer more benefits but require changing the whole food system. Future research should test how acceptable these dietary changes are in real life and include more environmental factors like biodiversity and pesticide use.