Population growth and changes in dietary practices globally have led to a tremendous rise in the demand for animal-source foods. While consuming the required amount of protein is fundamental to human health, protein needs can be met in many ways with animal- or plant-source foods. Increased consumption of meat and other animal-source foods worldwide is also connected to non-communicable diseases (NCDs), excessive individual intake, increased greenhouse gas emissions, and overutilization of water. Health and environment concerns exist because of the practices in livestock rearing, processing pre-packaged meat, and distribution. The conference \"Frontiers in Agricultural Sustainability: Studying the Protein Supply Chain to Improve Dietary Quality,\" held at the New York Academy of Sciences on December 12, 2013, explores sustainable protein innovations in food science and programming that are aimed at producing the required quality and quantity of protein to consumers worldwide. This Annals volume presents four papers stemming from this conference, discussing the importance of dietary protein for muscle health in inactive, hospitalized older adults; knowledge and tools to enhance resilience of beef grazing systems for sustainable animal protein production; impacts, efficiency, and sustainability of land-based production of animal protein; and cultured beef as an alternative to animal protein sources.