In this article, the long journey from the production of food ingredients to their transformation into nutrients was described. The essential function of nutrients is to satisfy the primary needs of living organisms, namely energy, morphology and reproduction, through the consumption of food. Fulfilling its primary role, food must contain nutrients that are essential for the well-being of the living, along with others that are not essential but are still important for proper metabolism. These substances are known as bioactive substances. The subject of this article is to describe the main bioactive substances, their extraction and purification processes, their biological role and the technologies used to enhance their absorption and bioavailability. In addition, their application in natural foods is described, where they are added to transform them into functional foods. A holistic description of nutrition cannot be achieved without providing information about additives and preservatives that are added to foods, to enhance their organoleptic characteristics and extend their shelf life, but compromise food safety. In addition to altering the properties of food, these substances are responsible for emerging metabolic pathologies that are rampant worldwide.