Host-plant selection is a key factor driving the ecology and evolution of insects. While the majority of phytophagous insects are highly host specific, generalist behaviour is quite widespread among bees and presumably involves physiological adaptations that remain largely unexplored. However floral visitation patterns suggest that generalist bees do not forage randomly on all available resources. While resource availability and accessibility as well as nectar composition have been widely explored, pollen chemistry could also have an impact on the range of suitable host-plants. This study focuses on particular pollen nutrients that cannot be synthesised de novo by insects but are key compounds of cell membranes and the precursor for moulting process: the sterols. We compared the sterol composition of pollen from the main host-plants of three generalist bees: Anthophora plumipes,Colletes cuniculariusand Osmia cornuta, as well as one specialist bee Andrena vaga. We also analysed the sterols of their brood cell provisions, the tissues of larvae and non-emerged females to determine which sterols are used by the different species. Our results show that sterols are not used accordingly to foraging strategy: Both the specialist species Andrena vagaand the generalist species Colletes cuniculariusmight metabolise a rare C₂₇sterol, while the two generalist species Anthophora plumipesand Osmiacornutamight rather use a very common C₂₈sterol. Our results suggest that shared sterolic compounds among plant species could facilitate the exploitation of multiple host-plants by A. plumipesand O. cornutawhereas the generalist C. cuniculariusmight be more constrained due to its physiological requirements of a more uncommon dietary sterol. Our findings suggest that a bee displaying a generalist foraging behaviour may sometimes hide a sterol-specialised species. This evidence challenges the hypothesis that all generalist free-living bee species are all able to develop on a wide range of different pollen types.