A sustainable agricultural and food system is characterized by two qualities: availability of high-quality, healthy food along with the best possible preservation of natural resources. Organic farming is discussed as a solution model for the complementary achievement of both aims. Taking the region Mostviertel-Eisenwurzen (A) as a case study, the present investigation examines the regional self-reliance in food production by means of three scenarios. In the basic scenario, the current land use of the region is set against the present-day food demand of the local population. The organic scenario assumes that the farming method of the region adheres 100% to the guidelines of organic farming. The food produced is set against the current food demand, as in the basic scenario. In the third scenario–-the organic-alternative scenario–-the 100% organically produced food is set against a food demand of the local population that follows the recommendations of nutritional science, comprising more plant-based diets. The results show that in the case of the hypothetical conversion to organic farming, food production decreases in absolute numbers. Despite this reduction, the local population can be sufficiently supplied with food energy, both in the case of the average Austrian diet as well as in a diet according to the recommendations of nutritional science. The number of people that can be supplied outside the region is higher in the nutritional science diet than in the average Austrian diet, despite the lower total net export quantity. While egg, meat and milk production are up to six times the local demand, the degree of self-supply of plant products (especially fruit and vegetables) covers only two-thirds of the demand after conversion. Moreover, our calculations show how a change of consumption patterns affects the demand for imported feedstuff. The region changes from being a net importer of concentrate (76,190 t fresh mass) at the starting point to a gross exporter (39,784 t fresh mass) in the organic and the organic-alternative scenario. In summary, agricultural production according to the guidelines of organic farming and a diet following the recommendations of nutritional science seems a promising strategy for achieving a sustainable agricultural and food system.