This paper investigates how a diet associated with the lowest possible environmental impacts might look and which effects on dietary balance and food self-sufficiency such a diet would have. For this purpose, an optimization model of the Swiss agricultural and food sector including imports was extended by life cycle assessment data for each product and process, by the Swiss dietary recommendations and by an energetic balancing of the domestic food production and consumption. The environmental impacts were quantified by the ReCiPe impact assessment method. Optimizing environmental impacts whilst fulfilling dietary recommendations and still using the whole Swiss agricultural area would almost halve the environmental impacts of food consumption. In order to achieve this, the average diet would need to change substantially, involving on the one hand a significant increase in the consumption of plant-based products such as grains or potatoes, nuts, and fruit and vegetables, and on the other hand, a sharp reduction in meat and alcohol consumption. These changes are associated with improvements in production processes ranging from reducing soybean meal in feedstuffs to giving preference to littleprocessed foods such as liquid rather than dried or processed milk. The results not only prove the synergistic effects between an environmentally friendly and a balanced diet, but also the simultaneously attainable increase of food self-sufficiency due to lower import levels, enhancing food security. With regard to the use of the large domestic areas of permanent grassland, the outcome is contradictory: The abandonment of these areas reducesddue to lower animal husbandrydthe environmental effects but increases dependence on imports and makes it more difficult to ensure the supply of nutrients originating mainly from animal products. A favorable option for improving both environmental impacts and food self-sufficiency is finally the avoidance of food waste. This would increase the potential to reduce the environmental impacts of food consumption to up to 75%.
