Composition of linear and branched short-chain fatty acids in human milk and newborn feces: influence of perinatal and maternal factors†

This research aimed to analyze the percentage of short-chain fatty acids (SCFAs) in human milk (HM) and newborn feces and to explore potential associations with factors such as maternal nutrition, age, biological sex, delivery mode, diet, and the type of HM. Gas chromatography was used to measure the percentage of SCFAs in colostrum (n = 23), transitional HM (n = 23), and mature HM (n = 92) and feces of newborn (n = 36) at day 30 postpartum. Anthropometry was also evaluated in the mother and the infant. The results showed that acetic acid was the most abundant in HM. The percentage of butyric acid and isovaleric acid was higher (p < 0.05) in the feces of newborns whose mothers were overweight/obese or were male, respectively, compared to newborns whose mothers were of normal weight or were female. The percentage of valeric acid was higher in the feces of newborns whose mothers were over 30 years old and who were delivered by C-section, compared to newborns whose mothers were 30 years old or younger and who were delivered vaginally. Inadequate intake of proteins, carbohydrates, and fiber was associated (p < 0.05) with lower acetic acid and higher butyric acid, higher propionic acid and lower butyric acid, and higher isovaleric acid percentage, respectively, in mature HM. The percentage of acetic acid was higher (p < 0.01) and that of propionic acid, butyric acid, isobutyric acid, and isovaleric acid was lower (p < 0.01) in colostrum compared to mature HM. The intake of lipids was associated with the percentage of butyric acid (β = −0.32, p = 0.01), and the percentage of propionic acid (β = 0.43, p < 0.01) was associated with carbohydrate intake. Overall, this study concluded that factors such as maternal nutritional status, diet, age, biological sex, and delivery mode were related to the composition of specific SCFAs in mature HM and newborn feces. Additionally, the percentage of SCFAs gradually decreased from colostrum to mature HM.