Discovered in 1954 as one of the first human milk oligosaccharides by Polonowski and Montreuil (Polonowski and Montreuil 1954). Its expression is regulated by the secretor gene which encodes the enzyme fucosyltransferase‑2. In combination with the Lewis blood group gene, four global types of milks have been identified that differ in their HMO composition.

2'‑FL is a trisaccharide formed of L-fucose linked with lactose (Fuc α1‑2 Gal β1‑4 Glc). It is the most abundant oligosaccharide in human milk with an average concentration of 2.4 g/l. 2'‑FL is present in milk of approx. 80% of mothers worldwide. This human milk oligosaccharide is a prebiotic candidate that deflects intestinal pathogens, is involved in immune system maturation (Castanys-Muñoz et al. 2013) and in cognitive development after little doses are absorbed into the circulation (Berger et al. 2020).