Prebiotics such as inulin (Inu)-type fructans and alternative natural sweeteners such as stevioside (Ste) become more popular as food ingredients. Evidence is accumulating that carbohydrates and carbohydrate-containing biomolecules can be considered true antioxidants, capable of scavenging reactive oxygen species (ROS). Here, we report on the ROS scavenging abilities of Inu and Ste in comparison with other sugars, sugar derivatives and arbutin. It is found that Inu and Ste are superior scavengers of both hydroxyl and superoxide radicals, more effective than mannitol and sucrose. Other compounds, such as 1-kestotriose, trehalose, raffinose and L-malic acid, also showed good reactivity to at least one of the two oxygen free radicals. The strong antioxidant properties of Inu and Ste are discussed. Within the plant vacuole, these compounds could play a crucial role in antioxidant defense mechanisms to help survive stresses. Addition to food assists in natural sweetening, food stabilization and maximizes health impact.