Natural Occurrence and Concentration
Human milk is unique with regard to its high content of complex oligosaccharides. The structural diversity and high concentration of complex oligosaccharides in human milk is specific to humans, and is not found in milk of dairy animals.
After lactose and proteins, human milk oligosaccharides represent the third largest fraction in human mothers’ milk. The natural concentration ranges from approximately 10 to 15 grams per liter. In contrast to bovine milk, human milk has a much higher concentration of carbohydrates / sugars and a significantly lower concentration of proteins.
More than 150 different human milk oligosaccharides have been identified in human milk, ranging from trisaccharides up to very complex structures made of more than 12 sugar residues. The most abundant human milk oligosaccharide is 2’-Fucosyllactose, which can be found in approximately 80% of human milk at concentrations of up to 2.5 grams per liter. Other abundant human milk oligosaccharides are 3-Fucosyllactose, Lacto-N-tetraose, Lacto-N-neotetraose, Lacto-N-fucopentaose and the sialic acid containing HMOs 3’-Sialyllactose and 6’-Sialyllactose.
These diverse structures are presumed to reflect the range of different functions of human milk oligosaccharides. Scientific studies have shown that some of these sugars may conduct antimicrobial effects on specific pathogens, and affect the composition of the gut microbiota by promoting the growth of specific beneficial bacteria.