After lactose and fat, HMOs are the third largest component of breast milk. They are a complex mixture of indigestible carbohydrates and have a high structural diversity. Over 150 different HMOs have already been identified.
The types and concentrations of HMOs vary greatly between breastfeeding women and also during the course of breastfeeding. Nevertheless, the two HMOs 2'-fucosyllactose (2'-FL; fucolysed) and lacto-N-neotetraose (LNnT; neutral) are found in human milk in the largest amounts.
Technical progress means it is now possible to produce HMOs industrially and add them to infant milks.