Preterm infants may show a higher risk of adverse health outcomes, such as the development of metabolic syndrome and cognitive impairment. The most recent evidence highlights that nutrition, body composition development, and early postnatal growth may play a role in the programming of these processes. Human milk feeding has been recommended as the natural feeding for preterm infants and as a cost-effective strategy for reducing disease and economic burden. Considering that the postnatal growth retardation and aberrant body composition shown by preterm infants at the time of hospital discharge still remain important issues, we performed a literature review, aiming to provide an update about the effect of human milk feeding on these processes. On the basis of our findings, human milk feeding in preterm infants, although related to a slower weight gain than formula feeding, is associated with a better recovery of body composition through the promotion of fat-free mass deposition, which may ultimately lead to better metabolic and neurodevelopmental outcomes. Promotion and support of human milk feeding should be considered a priority in preterm infants’ care.

The anti-infective properties of breast milk have been known for decades. In recent years, an increasing number of papers have described the variety of bioactive compounds that are present in breast milk with varying degrees of antiviral activity. However, to date, the totality of the properties of these compounds is not fully understood and, above all, their synergistic interaction is not yet known. The purpose of this review is to describe the current knowledge about the antiviral compounds in breast milk, both with specific and non-specific action against pathogens. Due to the current pandemic situation from SARS-CoV-2 (Severe acute respiratory syndrome Coronavirus-2), research has focused on a multitude of potential antiviral substances, taking breast milk as a biological model of reference. Future research is needed to expand the knowledge of these compounds, which will hopefully assist in the development of therapies applicable even at later ages.

Human breast milk not only has nutritional properties but also holds a functional role. It contains various bioactive factors (lactoferrin, lysozyme, leukocytes, immunoglobulins, cytokines, hormones, human milk oligosaccharides, microbiome, microRNAs and stem cells) shown to contribute to several short- and long-term health outcomes. Some of these factors appear to be involved in the infant’s neuro-cognitive development, anti-oncogenic processes, cellular communication and differentiation. Furthermore, breast milk is increasingly recognized to have dynamic characteristics and to play a fundamental role in the cross-talking mother-neonate. This narrative review aims to provide a summary and an update on these bioactive substances, exploring their functions mainly on immunomodulation, microbiome and virome development. Although the knowledge about breast milk potentiality has significantly improved, leading to discovering unexpected functions, the exact mechanisms with which breast milk exercises its bioactivity have not been completely clarified. This can represent a fertile ground for exploring and understanding the complexity behind these functional elements to develop new therapeutic strategies.

Preterm infants have a lower level of nutrient body stores and immature body systems, resulting in a higher risk of malnutrition. Imbalanced complementary feeding could lead to further risk of nutritional deficits and excesses. However, evidence on their nutritional requirements following hospital discharge is limited. When planning complementary feeding, appropriate micronutrient intake should be considered for their critical role in supporting various body functions. This narrative review summarizes the need for iron, zinc, vitamin D, calcium, phosphate and long-chain polyunsaturated fatty acids (LCPUFAs) supplementation in preterm infants during complementary feeding. Regarding iron and vitamin D, the scientific community is reaching an agreement on supplementation in some categories of prematures. On the contrary, there is still not enough evidence to detail possible recommendations for LCPUFAs, zinc, calcium and phosphorus supplementation. However, these micronutrients are paramount for preterms’ health: LCPUFAs can promote retinal and brain development while calcium and phosphorus supplementation is essential to prevent preterms’ metabolic bone disease (MBD). Waiting for a consensus on these micronutrients, it is clear how the knowledge of the heterogeneity of the prematures population can help adjust the nutritional planning regarding the growth rate, comorbidities and comprehensive clinical history of the preterm infant.