Current diets and food production practices are causing substantial environmental degradation on a global scale. The impacts caused by food production jeopardise ecological and climate stability and contribute to the transgression of environmental limits. Meanwhile, consumption of low-quality, nutrient-poor diets worldwide lead to different forms of malnutrition. One solution that could alleviate both environmental damage and malnutrition is dietary change.
Research on the sustainability of diets often employ interdisciplinary approaches which consider multiple criteria framed in wider environmental and socio-economic contexts. This thesis contributes to this body of research by advancing the application of life cycle assessment (LCA) and mathematical optimisation techniques. Insights are uncovered through three approaches which examine the environmental sustainability of dietary patterns using various methods and underlying concepts. First, Data Envelopment Analysis (DEA)–a linear programming (LP) method–is employed to provide a global environmental and nutritional assessment of national food supplies and gauge how efficiently food supply compositions convert environmental impacts into calories and nutrients. In the second analysis, an LP model is developed to identify nutritionally-adequate optimal diets within the environmental limits of the planet defined by the ‘planetary boundaries’ framework. Lastly, the global ecological and socio-economic externalities of national dietary patterns are estimated using a ‘true cost accounting’ method based on the monetarisation of life cycle impacts.
The global assessment using DEA reveals significant scope for countries to reduce the environmental impacts from their food without also having to decrease calorie and nutrient supply, particularly upper-middle- and high-income countries. Optimising the average diet of the UK–a high-income country with environmentally unsustainable food consumption patterns–yields diet compositions which meet, or close to meeting, downscaled planetary boundaries, but may have trade-offs with affordability. Finally, the global costs of food production to health, ecosystems and resource scarcity embedded in diets are revealed to be substantial but could be significantly reduced via shifts to more plant-based diets in developed regions.