Multi-objective optimization of national dietary guidelines: balancing nutrition, environment, and economy.

Background: National dietary guidelines have largely overlooked the environmental sustainability of food systems. A multi-objective optimization framework to evaluate trade-offs among nutritional requirements, greenhouse-gas emissions, and economic costs across four countries at different development stages-the United States, China, Australia, and New Zealand. Methods: Using epidemiologically informed nutrient constraints and life-cycle environmental data, we systematically evaluate dietary scenarios that optimize animal-product consumption while ensuring essential nutrient adequacy. Results: Our analysis shows that strategic reductions in beef consumption can lower diet-related greenhouse-gas emissions by 28-62%, while chicken and eggs are reallocated to maintain nutritional integrity. Economic impacts vary markedly: vitamin-optimized scenarios reduce costs by 23% in China but increase costs by 19% in Australia. Conclusion: The results reveal distinct optimization pathways that necessitate tailored policy measures. This framework enables policymakers to revise food-based dietary guidelines to align with climate commitments while safeguarding nutritional security and economic viability across diverse national contexts.