Proteins are an essential part of the daily diet. They are major functional and structural components of all body cells, and participate in virtually all biological processes. The roles of proteins expand beyond their role in maintaining body protein mass and satisfying metabolic demands for biosynthetic pathways. Other important body functions include immunity and host defenses, linear growth and associated mental development. Foods from both animal and plant sources may contain similar levels of protein. Diets rich in plant-based foods and with fewer animal source foods commonly provides more fiber and less saturated fat and confers both improved health and environmental benefits. However, indiscriminate recommendations to increase plant-based foods may lead to unintended dietary consequences such as the risk of inadequate supply of protein, so attention need to be given to that. This brochure is a compilation of recent science on proteins done by Proteins and Nutrition Expert Networks at Nestlé Research.