The concentration of medium-chain fatty acids in breast milk is influenced by maternal diet and associated with gut microbiota in infants

Medium-chain fatty acids (MCFAs) have been shown to play a potential role in the infants' microbiota. We enrolled 50 mothers-infants' pairs and both breast milk and infants' fecal samples were collected. Breast milk MCFAs were determined by high performance liquid chromatography-tandem mass spectrometry, and whole genome shotgun sequencing was applied to determine the microbial composition. We identified that the content of MCFA varies greatly under the influence of the mother's individual factors, diet, and region, and edible oil is highly associated with MCFAs. Infants fed breast milk with low C6:0 tertile (7.57–24.20 pmol/g) showed a higher abundance of Salmonella . High (55.03–151.20 pmol/g) and medium (25.08–52.98 pmol/g) breast milk C6:0 tertiles were associated with a relatively high abundance of Clostridioides and Eubacterium . KEGG pathway revealed that C6:0 and C12:0 might potentially regulate amino acid and lipid metabolism. These findings may illustrate the potential bond between maternal and infant metabolism via MCFAs. A certain maternal diet, particularly edible oils, is associated with MCFAs in breast milk and further influence the abundance of specific intestinal microbes in infants, such as Clostridium, Eubacterium , and Salmonella . The levels of C6:0 and C12:0 were correlated with an increased presence of specific enzymes, which corresponds to the potential regulatory function of amino acid and lipid metabolism. MCFAs, Medium-chain fatty acids; C6:0, Caproic acid; C12:0, Lauric acid; KEGG, Kyoto Encyclopedia of Genes and Genomes. • Maternal diet is strongly linked to medium-chain fatty acids (MCFAs) in breast milk. • Breast milk C6:0 could inhibit Salmonella by regulating the butyricogenic bacteria. • MCFAs may exert antibacterial effects by influencing specific amino acid metabolism.