The role of protein quality in designing sustainable food systems.

The influence of protein digestibility and the adequacy of indispensable amino acids (IAAs) on designing sustainable food systems is not yet fully understood. In this study, we used FOODSOM (FOOD Systems Optimization Model) to evaluate the effects of including total or digestible protein and IAA requirements on land use and dietary outcomes of the Dutch food system. Our results show that land use is minimal with 18 g of animal-source protein per person per day. We also demonstrate that diets that meet all nutrient requirements, including protein, automatically satisfy IAA requirements. However, in digestible form, IAA requirements are met only when digestible protein requirements are considered alongside other nutrient requirements. Depending on the amount of animal-source protein in the diet, nutrients other than digestible protein and IAAs can be limiting and therefore influence land use. To ensure nutrient adequacy of advised diets, therefore, future food system modelling studies should include protein digestibility in addition to all macro- and micronutrient requirements. Only then, such modelling studies can explore the land use consequences of diets varying in the amount of plant and animal-source food, while assuring nutrient adequacy.