Abstract
Introduction: Tunisia experiences high prevalence of overweight, obesity and co-morbidities, and faces environmental issues such as water deprivation. Individual food choices have the potential to influence both public health and the environment. This study aimed to identify more sustainable diets for Tunisian adults, i.e. diets that are nutritionally adequate, culturally acceptable, and with low environmental impact. Methods: Individual dietary data from the nationally representative Tunisian study on food consumption (n=7209, 35-70y) were used together with the national food composition table. Diet-related environmental impact was assessed through 7 metrics – water deprivation, land-use, and its impacts on loss of biodiversity, erosion resistance, mechanical filtration, groundwater replenishment, biotic production– estimated for 138 foods. Quadratic optimization models were applied to obtain diets that meet nutritional recommendations while departing the least from the food content of the mean observed diet (OBS), and respecting increasingly stringent constraints on the environmental impact of the modeled diets. Results: Without environmental constraints, the main dietary shifts induced to meet nutritional recommendations were an increase of dairy, starch and vegetables, a decrease of foods high in fat/salt/sugar (HFSS) and added fats. The environmental impact of diet increased: +32 % for water deprivation and +46-48 % for land use and its impacts. When moderate environmental impact reduction (≤30%) constraints were added to nutritional constraints, the dietary shifts at the food group level were similar to that required to reach nutritional adequacy alone, except a progressive decrease in Meat/Fish/Eggs quantities. Animal-based products contributions to total energy and protein contents were close or slightly lower than in OBS, but a rebalance of sources was required: less meat in favor of dairy, eggs and fish products. Stronger reductions (≥40%) required more substantive shifts that might compromise the acceptability of optimized diets. Conclusions: Targeting a nutritionally adequate diet without considering its environmental impact might increase diet-related water deprivation, land use and its impacts on biodiversity and soil quality. In Tunisia, moving towards healthy diet with lower environmental impact does not rely on reducing the total share of animal-based products but on rebalancing their sources, together with a decrease of HFSS and added fats, and an increase of vegetables. Conflict of Interest: There is no conflict of interest