Book excerpt: Nutrition is a topic of wide interest and importance. In spite of growing understanding of the underlying biochemistry, and health campaigns such as 'five-a-day', increasing obesity and reported food allergies and eating disorders, as well as the widely advertised 'supposed' benefits of food supplements mean that a clear explanation of the basic principles of a healthy diet are vital. In this Very Short Introduction, David Bender explains the basic elements of food, the balance between energy intake and exercise, the problems of over- and under-nutrition, and raises the question of safety of nutritional supplements. ABOUT THE SERIES: The Very Short Introductions series from Oxford University Press contains hundreds of titles in almost every subject area. These pocket-sized books are the perfect way to get ahead in a new subject quickly. Our expert authors combine facts, analysis, perspective, new ideas, and enthusiasm to make interesting and challenging topics highly readable.