How does diet influence heart disease, cancer, diabetes, osteoporosis and kidney disease? What is its role in hypertension and obesity? Can an altered diet reduce risk of disease, make people healthier, and contribute to longer life expectancy? Can we use the knowledge we have about nutrition more effectively? What are the economic and social implications of changing the diets of entire populations? Can anything be learned from the history of public health and disease patterns? These and other questions were considered by experts from around the world at a symposium co-sponsored by the Royal Society of Canada and the Food and Nutrition Board of the US National Academy of Sciences. This work reports the results of these discussions. The role of diet in health and disease has been the subject of much general discussion in the media; major reports were recently issued by the us Surgeon General as well as by the National Academy of Sciences. In Canada, the Department of National Health and Welfare is considering dietary recommendations designed to reduce the risk of disease and improve health. This book is intended for students of nutrition and physiology.