Human Milk Oligosaccharides (HMOs) are the third largest solid component in breast milk (after fat and lactose), with functions such as regulating immunity, helping brain development, and regulating gut microbiota. They are known as the "soft gold" of breast milk. The average content of HMOs in human colostrum is 20.9g/L, which is 10-100 times higher than other mammalian milk. Its rarity and unique nutritional value make it a "noble" in the dairy industry, making milk powder products infinitely close to breast milk standards and almost becoming the ultimate goal of all infant and toddler dairy companies.
Scientists have found that there are over 200 different monomers of HMOs in breast milk, which are formed by five monosaccharides extending their sugar chains or undergoing fucosylation and sialylation on the basis of their core structure. The most important ones are six: 2 '- FL (2' - halophilic lactose), 3-FL (3-halophilic lactose), LNT (lacto-N-tetraose), LNnT (lacto-N-tetraose), 3 '- SL (3' - sialyllactulose), and 6 '- SL (6' - sialyllactulose). The diversity of combinations of different monosaccharide structures endows HMOs with various excellent functions.