Energy, Fatty Acid, and Cytokine (TNF-α and IL-10) Content in Mature Human Milk: Comparison between Foremilk, Middle Milk, and Hindmilk Breastfeeding Intervals

Human milk is a dynamic biological fluid whose composition varies throughout lactation, adapting to meet the physiological needs of the newborn. This study investigated how the breastfeeding time (foremilk, middle milk, hindmilk) affects energy, fatty acid, and tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) contents in mature human milk from five distinct donors (M1-M5), using creamatocrit, gas chromatography, and enzyme-linked immunosorbent assays, respectively. The results progressively increased in energy values, with the highest values in hindmilk. Fatty acid composition exhibited distinct individual profiles, with palmitic acid predominating in M1 and M5, and oleic acid more prominent in M2, M3, and M4. The duration of breastfeeding significantly influences the caloric and lipid composition of mature human milk. Principal component analysis (PCA) accounted for 59.6% of the variance, indicating the clustering of fatty acid profiles according to collection times from the same donor. No consistent pattern was observed for the immunological factors throughout the lactation. TNF-α was undetectable in some samples, possibly due to its low concentration in mature human milk, while IL-10 was consistently detected. These findings suggest that individual factors such as maternal diet, body composition, and lifestyle may influence the nutritional and immunological composition of human milk.