From the moment of birth, the diet must aim an optimal development of the full-term, healthy newborn, and the best known option until now is the breast milk. Studies have consistently highlighted the benefits of natural nutrition, emphasizing its nutritional qualities but also its role in developing immunity for the newborn. A curent challenge is the moment of initiating food diversification, with recommendations indicating ages between 4 and 6 months. Therefore, an analysis of existing recommendations should be linked to studies on the onset of food allergies with the initiation of diversification. There are also cases in which the natural diet cannot be achieved, in these situations the administration of milk formulas is required. Infant mill formulas have evolved a lot in terms of quality and composition, approaching the breast milk, but they can not be considered equal to it.