OBJECTIVE: To specify the principles, definition and dimensions of the new nutrition science. PURPOSE: To identify nutrition, with its application in food and nutrition policy, as a science with great width and breadth of vision and scope, in order that it can fully contribute to the preservation, maintenance, development and sustenance of life on Earth. METHOD: A brief overview shows that current conventional nutrition is defined as a biological science, although its governing and guiding principles are implicit only, and no generally agreed definition is evident. Following are agreements on the principles, definition and dimensions of the new nutrition science, made by the authors as participants at a workshop on this theme held on 5-8 April 2005 at the Schloss Rauischholzhausen, Justus-Liebig University, Giessen, Germany. RESULT: Nutrition science as here specified will retain its current 'classical' identity as a biological science, within a broader and integrated conceptual framework, and will also be confirmed as a social and environmental science. As such it will be concerned with personal and population health, and with planetary health--the welfare and future of the whole physical and living world of which humans are a part.