Climate impacts and monetary costs of healthy diets worldwide

About 2.8 billion people worldwide cannot afford the least expensive foods required for a healthy diet. Since 2020, the Cost and Affordability of a Healthy Diet (CoAHD) has been published for all countries by FAO and the World Bank and is widely used to guide social protection, agricultural, and public health and nutrition policies. Here, we measure how healthy diets could be obtained with the lowest possible greenhouse gas (GHG) emissions, in ways that could further inform food choice and policy decisions toward sustainability goals. We find that the lowest possible GHG emissions for a healthy diet in 2021 would emit 0.67 kg CO2e (SD=0.10) and cost USD 6.95 (SD=1.86) per day, while each country's lowest-priced items would emit 1.65 kg CO2e (SD=0.56) and cost USD 3.68 (SD=0.75). Healthy diets with foods in proportions actually consumed in each country would emit 2.44 kg CO2e (SD=1.27) and cost USD 9.96 (SD=4.92). Differences in emissions are driven by item selection within animal-source foods, and starchy staples to a lesser extent, with only minor differences in other food groups. Results show how changes in agricultural policy and food choice can most cost-effectively support healthier and more sustainable diets worldwide.