Characterization of Human Milk and the Gut Microbiota in Healthy Women During the Postpartum Period

Background/Objectives: Early microbial colonization in infants is known to be the key to establishing a healthy microbial community in later life stages. Breast milk is an optimal source of macro-micronutrients for newborns as well as a potential source of bacteria. Thus, we aimed to compare the microbial composition of breast milk and maternal fecal samples in our study. Methods: We recruited 20 healthy women on the 15th postpartum day. We excluded women who had any acute or chronic disease or who were using drugs or probiotics. We recorded the sociodemographic characteristics of the participants and performed anthropometric measurements. We obtained maternal fecal and mature breast milk samples. We determined the microbiota composition of these samples via 16S rRNA next-generation sequencing and calculated the Shannon index. Results: The mean age of the breastfeeding women was 24.2±2.94 years. Both the maternal fecal and mature breast milk microbiota were dominated by the phylum Firmicutes (50.2% vs. 72.8%, respectively). However, the predominant bacterial families were Ruminococcaceae (14.2%) in the maternal gut and Streptococcaceae (42.0%) in the breast milk. However, there were relatively high higher levels of Prevotella, Faecalibacterium, and Akkermansia in the fecal samples, whereas Streptococcus, Staphylococcus, and Proteus were detected in the breast milk samples. Additionally, the microbial diversity of breast milk was significantly lower than the maternal fecal samples. Conclusions: The results indicate that there is a similarity between the intestinal microbiota of lactating women and the microbiota of breast milk. However, human milk and maternal gut microbiota are associated with higher levels of certain bacterial species, suggesting that breast milk and maternal microbiota interact.