Human milk composition exhibits considerable inter- and intraindividual variation. With metabolomics we
aim to understand the factors affecting the dynamic changes in the human milk critical for infant development and health, including brain development, immune function, and gut microbiota. This presentation focuses on the associations of maternal distress and milk cortisol with human milk metabolites (1), milk cortisol with human milk lipid composition (2), and the stage of lactation with human milk oligosaccharides (HMO) (3). In study 1, the associations between maternal psychological distress, milk cortisol levels, and the human milk metabolome were investigated with targeted NMR metabolomics. The metabolites associated with self-reported symptoms of depression and anxiety or with milk cortisol were shown to be dissimilar, pointing toward stress-related changes in microbiome–gut–brain axis and energy metabolism, respectively. Further in study 2, the interactions between milk cortisol and lipids in human milk were examined. The results pointed to cortisol’s potential influence in the release of medium- and intermediate-chain fatty acids from maternal body stores. In study 3, the metabolite profiles of Chinese human milk across different lactation stages up to 8 months postpartum were explored. The research identified significant differences in the individual HMOs and in the development of the HMO profiles over the course of lactation between secretors and non-secretors. Small levels of 2’-fucosyllactose and lacto-N-fucopentaose I typically absent in non-secretor milk were measured, which is consistent with prior studies suggesting that Chinese non-secretors have some fucosyltransferase 2 enzyme activity. Together, these studies provide new insights into factors affecting the human milk metabolome and lipid composition.