Agriculture and food production contribute significantly to greenhouse gas emissions and environmental pollution. Shifting human dietary patterns has the potential to reduce such environmental harms while also promoting human health. Government policy, in the form of the United States Dietary Guidelines (USDG), recommends what Americans should eat and could play an important role in shifting the food system to one that is more sustainable. However, the USDG are an overlooked aspect of U.S. food policy. While many countries have moved to synthesize environmental goals with dietary guidance, the United States has taken the opposite approach. In 2015, despite recommendations from the expert panel appointed under the Federal Advisory Committee Act (the Dietary Guidelines Advisory Committee), which recommended including sustainability considerations in the 2015 USDG, the Secretaries of Health and Human Services and Agriculture rejected those recommendations reasoning that the sustainability perspective was beyond the scope of the USDG-enabling statute. This Article examines why that decision was wrong and how, based on international examples and sound science, the federal government should see the USDG as a powerful food system policy tool that can be used to promote human and environmental health in the 21st century.