Accounting for differences in bioavailability of calcium, iron, and zinc among individual foods for deriving sustainable healthy diets

The advocated shift from diets high in animal-source food toward healthy, plant-based diets has raised concerns for adequate nutrient intake, especially for those nutrients that are more bioavailable in animal-source foods compared to plant-source foods. To date, global food system optimisation models have not accounted for differences in nutrient bioavailability, which could lead to an overestimation of nutrient availability in healthy, plant-based diets. We used the results of an existing food system optimization model – the Circular Food Systems (CiFoS) model – to assess the impact of accounting for the bioavailability of iron, calcium and zinc. Nutrient content of individual food items in the model were recalculated based on bioavailability fractions, while also accounting for bioavailability in the nutrient requirements used as model constraints. Using bioavailable nutrient content affected i) the quantity of foods that need to be produced and consumed, ii) the types of foods within food groups, and iii) the environmental impact of the food system. The dietary amount of animal-source protein was not affected by using bioavailable nutrient content, and any emerging nutrient gaps were filled mainly by grains and vegetables. Finally, meeting the nutrient requirement constraints was the largest driver for food system changes, with tighter model constraints for nutrient requirements leading to an environmental trade-off due to an increase in crop production. These results highlight the relevance of accounting for bioavailability when studying sustainable healthy diets, while acknowledging the methodological challenges of doing so in global food system models.