Nonnutritive sweeteners are not supernormal stimuli

BACKGROUND: It is often claimed that nonnutritive sweeteners (NNS) are 'sweeter than sugar', with the implicit implication that high-potency sweeteners are supernormal stimuli that encourage exaggerated responses. This study aimed to investigate the perceived sweetness intensity of a variety of nutritive sweeteners (sucrose, maple syrup and agave nectar) and NNS (acesulfame-K (AceK), rebaudioside A (RebA), aspartame and sucralose) in a large cohort of untrained participants using contemporary psychophysical methods. METHODS: Participants (n = 401 total) rated the intensity of sweet, bitter and metallic sensations for nutritive sweeteners and NNS in water using the general labeled magnitude scale. RESULTS: Sigmoidal dose-response functions were observed for all stimuli except AceK. That is, sucrose follows a sigmoidal function if the data are not artifactually linearized via prior training. More critically, there is no evidence that NNS have a maximal sweetness (intensity) greater than sucrose; indeed, the maximal sweetness for AceK, RebA and sucralose were significantly lower than that for concentrated sucrose. For these sweeteners, mixture suppression due to endogenous dose-dependent bitter or metallic sensations appears to limit maximal perceived sweetness. CONCLUSIONS: In terms of perceived sweetness, NNS cannot be considered supernormal stimuli. These data do not support the view that NNS hijack or overstimulate sweet receptors to produce elevated sweet sensations.