Maternal obesity increases breast milk bile acid levels.

Context: Breast milk (BM) provides the optimal combination of essential nutrients and bioactive molecules for infant growth and development. However, accumulating evidence from our group and others indicates that maternal factors such as obesity can alter BM composition, potentially affecting offspring health outcomes. Bile acids (BA), both primary and secondary, have been identified in human BM but the precise composition and their role in BM remain largely underexplored. In this study, we analyzed BA profiles in BM and plasma in lactating mothers with obesity or not, across two independent clinical cohorts.

Methods: BM and plasma samples were collected from breastfeeding women classified as normal-weight (N) or with obesity (O). BA concentrations were quantified by reverse phase liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS).

Results: BAs were present in BM, primarily as glyco- and tauro-conjugated of the primary BAs cholic (CA) and chenodeoxycholic acid (CDCA), though at lower levels than in plasma under normal-weight conditions. Maternal obesity led to a marked increase in total BM BA levels while plasma BA concentrations and composition remained unchanged. Additionally, BM BA levels were positively correlated with maternal pre-pregnancy BMI, circulating leptin (a marker of adiposity), and insulin levels.

Conclusions: Our findings identify maternal obesity as a significant modifier of BM BA composition, with potential implications for neonatal digestion, maturation and health. Further research is warranted to elucidate the impact of these alterations on infant health and development.