Making food systems more sustainable is one of humanity's largest challenges. Over two decades of life cycle assessment research on the environmental performance of food systems has helped to inform efforts to address this challenge. In recent years, there has been much interest in aggregating the results of these studies at scales of national production, dietary patterns, and future food scenarios. The process of comparing impacts of diverse products based on extant literature presents numerous challenges which have been inadequately addressed. Drawing upon examples of greenhouse gas emissions and seafood systems, we suggest best practices to support more complete, consistent, and comparable aggregation practices. Ultimately this would lead to more robust industry and consumer decisions and public policy. We suggest to: 1) define product groups reflecting impact drivers and in accordance with study goals, 2) select studies in a transparent way whose methods are consistent, and 3) assess results in the context of actual production or consumption patterns. Applying these practices would strengthen food life cycle assessment aggregation studies as a tool guiding towards sustainable food systems. © 2022 The Authors