Decoding the human milk virome: a comparative analysis of composition, colonization, and health impacts

Breast milk (BM) is a complex biological system that not only delivers essential nutrition to the baby, but is also a rich collection of microorganisms, including bacteria, viruses and fungi. Dominated by bacteriophages and eukaryotic viruses, the BM virome plays a role in shaping the infant gut microbiome composition, influencing immune development and long-term health outcomes. Emerging research confirms the vertical transmission of bacteriophages from the mother to her infant via breastfeeding, and the shared viral taxa suggest functional roles in modulating bacterial populations and maintaining gut homeostasis. Disruptions in this early life virome, driven by factors such as maternal health, mode of delivery, and geographic location, have been linked to dysbiosis and disease susceptibility for conditions ranging from inflammatory bowel disease to metabolic disorders.

A systematic literature search was conducted in NCBI/PUBMED and the European Nucleotide Archive (ENA) using the keywords "Milk virome," "Milk phage," "Milk phageome," and "Milk metagenome". After applying our inclusion and exclusion criteria, two studies remained. This comparative analysis explores the composition and diversity of the BM virome across two geographically distinct cohorts-Turkey and the United States-revealing significant differences in viral diversity and composition.

The Turkish cohort exhibited a significantly higher viral richness and unique taxonomic distributions compared to the USA group. Notably, bacteriophage families like Myoviridae, Siphoviridae, and Podoviridae were shown to be abundant in both populations. The Turkish BM virome featured a higher prevalence of plant- and insect-derived viruses (e.g. Partitiviridae, Tospoviridae), likely tied to dietary or regional agricultural practices.

Despite limitations related to sample size and methodological variability, this study emphasizes how dietary habits, environmental exposures, and geographic location may shape the breast milk virome. Further research integrating longitudinal data from a multi-ethnic population, cohorts is essential to fully harness the diagnostic and therapeutic potential of the human milk virome.