Few, if any, would contest that diet and nutrition have a crucial and substantial impact on human health. But the devil is in the details. Common questions include: is there such a thing as an optimal diet? What is suboptimal? Which dietary components matter most? And given the necessity to take action on climate change and planetary health, what should the world eat?1 The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) contributes towards answering these questions by estimating the burden of mortality and disability attributable to specific dietary risks, within a comparative risk assessment framework that currently considers 84 behavioural, environmental, occupational, and metabolic risks across 195 countries and territories.