Carbon-costed diets highlight redistribution needs: evidence from 165 countries

Food-system greenhouse gas emissions (GHGE) impose large social costs that are rarely reflected in food prices. The affordability impacts of internalising these costs remain unclear. Carbon pricing is a key instrument for internalising environmental costs, yet its application to food systems has been constrained by concerns over food affordability and distributional equity. Here, we integrate dietary intake, country-specific environmental footprints, food prices, and income distributions with MATILDA (Micro–Macro Assessment Tool to Identify Low-impact Dietary Actions) to estimate market and carbon-inclusive dietary costs across 165 countries and socio-demographic groups. We examine how internalising the social cost of diet-related GHGE alters dietary affordability globally and regionally. Our results reveal profound inequalities in the economic and environmental burdens of food consumption. Across regions, the inclusion of GHGE costs to food prices raises the cost of diets by 8–32%, limiting food affordability for an additional 397 million people worldwide. Low-income populations in sub-Saharan Africa and Southern Asia are particularly vulnerable, while full-pricing of diets in high-income regions has minimal impact on food affordability. These findings underscore the importance of coupling dietary transitions with redistributive and environmental pricing policies to ensure that food system decarbonisation does not exacerbate global nutrition inequities.