Aspartame ingested without tasting inhibits hunger and food intake

The effects on motivation to eat and food intake of administering small amounts of aspartame (234 to 470 mg: lower dose equivalent to the amount of aspartame contained in 1-2 cans of some soft drinks) in capsules to human volunteers were examined in two separate experiments (the second was a replication of the first). The results provided clear evidence of a prominent postingestive inhibitory action of aspartame on appetite: consumed in capsules, aspartame reduced subsequent food intake and, to a lesser extent, motivation to eat. The mechanism underlying this effect has yet to be elucidated. A possibility is that the release of cholecystokinin by phenylalanine, a constituent of aspartame, is involved. A further result was that drinking aspartame-sweetened water did not reliably reduce motivational ratings or food intake (in the first experiment aspartame ingested in capsules significantly reduced food intake compared with the same amount ingested as a sweet drink). One interpretation of these together with previous findings is that the response to consuming aspartame is determined by at least two interacting influences: an inhibitory postingestive effect and a stimulatory effect of its sweet taste. In turn, the relative potency of these influences may be modified by certain other features of the aspartame-sweetened food or drink (e.g., its nutrient content). Another implication of these results is that it cannot be assumed that intense sweeteners will all have equivalent effects on appetite.