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Abstract

Middle-income countries face challenges in achieving diets that are both nutritionally adequate and environmentally sustainable, while income-related dietary heterogeneity adds uncertainty to population-wide dietary transitions. Here we investigate how income inequality shapes long-term dietary transitions from nutritional and environmental perspectives. We project Brazilian dietary patterns from 2020 to 2100 in scenario-based income pathways by integrating national-representative survey data with nutritional and environmental databases. We find that reducing income inequality improves dietary nutritional quality by 5.7%, and avoids 40-50% of the increase in dietary environmental impacts projected under income-inequality-increasing scenarios by 2100. However, inequality reduction is associated with a short-term worsening of dietary environmental impacts, with an average deterioration of 2.2% relative to the baseline scenario. These results highlight a trade-off between short-term environmental pressures and long-term nutrition and sustainability benefits, underscoring that income inequality reduction alone is insufficient and should be complemented by broader policy packages to promote dietary transitions.