The book is devoted to fundamental and applied aspects of the problems of nutrition and food assimilation. Within the framework of the new interdisciplinary science of trophology, the main postulates of the theory of adequate nutrition are formulated, of which the classical theory of balanced nutrition is included as an important component. The main flows coming from the gastrointestinal tract into the internal environment of the body, endoecology and its main physiological functions, the role of the intestinal hormonal system in the life of the body, the general effects of this system and its role in the development of the specific dynamic action of food are characterized. The origin of life, the emergence of cells, trophic chains, etc. are considered in the light of trophology, as well as some of its biological aspects. It is shown that the trophological approach is fruitful for understanding the processes of assimilation of nutrients at all levels of organization of living systems, as well as for biology in general , as well as for some general problems of preventive and clinical medicine. The book is intended for a wide range of trained readers whose interests include biological, technological, humanistic, environmental, medical and other problems of nutrition and digestion.