Review of sustainable diets: are nutritional objectives and low-carbon-emission objectives compatible?

Food systems in developed countries face one major challenge, namely the promotion of diets that are both healthy and generate less greenhouse gas emissions (GHGE). In this article, we review papers evaluating the impact of a change in diets on both health and GHGE. We address the following questions: How big are the health and environmental impacts that could be induced by a switch to healthier diets? In monetary value, what is the relative importance of the health impact and the environmental impact? Is it possible to design an economic policy to increase global welfare that also takes into account the externalities on both health and the environment? Since the way the change in diet is modeled is a key issue, we classify papers according to the methodology used for simulating diet changes: ad hoc scenarios, optimized diets, and economic modeling. We find that it is possible to design economic policies that have positive impacts on both dimension. Because the substitutions/complementarities between food products are complex, it is not granted that a policy targeting one dimension will generate positive effects on the other dimensions. However, given the diversity of substitution and the complementarity possibilities between products, it is possible to design a policy that does improve both dimensions. A carbon-based tax policy that targets the products with a high greenhouse gas content (e.g., meat products) and reinvests the revenues collected with the tax to subsidize the consumption of fruit and vegetables, is likely to have positive effects on both dimensions.