Using X-ray diffraction technique, we investigated the modulation of the bicontinuous cubic structure of monoacylglycerol (monoolein)-water systems by the presence of solutes. X-ray diffraction results demonstrated that chaotropic solutes (NaSCN, NaI, and urea) expand the lattice constants of fully hydrated monoolein in Pn3m cubic phase and on the other hand, that kosmotropic solutes (Na2SO4, NaCl, and sucrose) reduce the lattice constants. These results can be interpreted as suggesting that kosmotropes reduce the interfacial area and that chaotropes expand the interfacial area, by assuming independence of the molecular length of monoolein on the presence of solutes.