BACKGROUND: Breastfeeding is the ideal method of feeding for all newborns and is associated with multiple positive health outcomes. Human milk provides all essential nutrients and bioactive molecules needed for optimal infant health and development. Maternal nutrition during lactation plays an important role in supporting breastfeeding and in preventing nutrition and metabolic imbalances. The aim of this narrative review was to describe the most prevalent nutrition issues in lactating women and provide a summary of current diet recommendations as well as controversies on supplementation, in order to facilitate the information for clinicians and health professionals. SUMMARY: Breastfeeding is a nutritionally demanding stage and adequate nutrition is key to avoid alterations in maternal nutritional status, to produce an adequate quantity of milk with good quality, and to avoid nutrition programming of diseases. Anemia and vitamin D, A, iodine, and iron deficiencies are common, while obesity and metabolic diseases keep rising. Inadequate maternal intake of many nutrients is also frequent in this stage.