Book excerpt: Consumer interest in diet and nutritional supplements is increasing dramatically. Patients and members of the public are seeking advice from health professionals, nutritionists and food scientists. This book is designed to meet the needs of those professionals who are called upon to advise patients and the general public. It provides also a valuable text for those who are researchers or decision makers in the food and pharmaceutical industries. The text presents a thorough account of this topical subject and enables the reader to appreciate the functions of nutrients in health and common disease states, to understand the current debates over the roles of nutrients and supplements in the diet, and to answer those questions frequently asked by patients and consumers.