How do maternal lifestyle factors influence the microbial composition of human breast milk? A narrative review by UniPv and Spoke 5

A research group from Spoke 5 at the University of Pavia has published a new article on the composition of human breast milk (HBM). This narrative review summarises the current understanding of how maternal lifestyle habits—such as diet, physical activity, sleep quality, smoking, and alcohol consumption— influence HBM microbiota.

The research group is affiliated with the Laboratory of Dietetics and Clinical Nutrition, coordinated by Prof. Hellas Cena. This review is part of Spoke 5 activities related to the LIMIT study.

Human breast milk (HBM) is considered the gold standard for infant nutrition due to its optimal nutrient profile and complex composition of cellular and non-cellular components. Breastfeeding positively influences the newborn’s gut microbiota and health, reducing the risk of conditions like gastrointestinal infections and chronic diseases (e.g., allergies, asthma, diabetes, and obesity). Research has revealed that HBM contains beneficial microbes that aid gut microbiota maturation through mechanisms like antimicrobial production and pathogen exclusion.

The HBM microbiota composition can be affected by several factors, including gestational age, delivery method, medical treatments, lactation stage, and maternal lifestyle habits such as diet, exercise, sleep quality, smoking, alcohol use, and stress. Particularly, lifestyle factors can significantly shape HBM microbiota by directly affecting its microbial composition or by altering the maternal gut microbiota, which then impacts HBM microbes via the enteromammary pathway.

The findings suggest that maintaining a healthy lifestyle during pregnancy and lactation is essential not only for the mother’s well-being but also for shaping the infant’s gut microbiota and immune system development.

While the influence of maternal diet on HBM microbiota is well-documented, indicating that dietary patterns, especially those rich in plant-based proteins and complex carbohydrates, can positively influence HBM microbiota, the impact of other lifestyle factors remain underexplored.

Current evidence indicates that lifestyle modifications during pregnancy and lactation could positively affect breast milk microbiota and, in turn, the infant’s health. However, more research, particularly longitudinal and interventional studies, is needed to fully understand the extent of these influences and to develop tailored recommendations.

Health professionals should integrate these findings into prenatal and postnatal care, advising mothers on the importance of maintaining a balanced diet, engaging in regular physical activity, and managing stress to promote optimal HBM composition. Additionally, public health policies must account for these factors when developing breastfeeding support programs, ensuring that maternal well-being is prioritised for the benefit of both mother and child.

A deeper understanding of how maternal lifestyle shapes HBM microbiota is crucial for designing effective interventions that promote infant health. Future research should focus on filling the gaps in our knowledge, particularly in areas like physical activity and stress, to develop comprehensive guidelines that will enhance breastfeeding practices and optimise long-term health outcomes for both mothers and their children.

At the same time, it is crucial to highlight that methodological and scientific limitations in studying the HBM microbiota, including inconsistencies in sampling, low microbial biomass, biases in detection technologies, and lack of functional insights, need to be addressed to gain more in-depth, accurate, and complete understanding. Standardising protocols, using multi-omics approaches, and adopting longitudinal designs can help mitigate some of these limitations.