The ability of a multicellular organism to prevent the harmful microorganisms from causing damage to it is known as immunity. It is broadly categorized into innate immunity and adaptive immunity. Innate immunity consists of a preconfigured response which is used to respond to a wide range of situations and complications. Adaptive immunity, on the other hand, covers the learned responses to molecules which the body has faced previously. Consumption of a proper and balanced diet is important for the healthy functioning of the immune system. There are also some particular nutrients such as vitamin C, vitamin D, zinc, selenium, iron and protein which are important to the growth and functioning of the immune system. This book includes some of the vital pieces of work being conducted across the world, on various topics related to diet and immune functions. It strives to provide a fair idea about this discipline and to help develop a better understanding of the latest advances within this field. Researchers and students in this field will be assisted by this book.