Aspartame, also known as 'Equal' (table top use) or 'Nutrasweet' (as a food additive) increases aggresion in mice due to altered seratonin handling in the brain and reduces cognition i.e. the rate at which mice learn to get through a maze [Goerss AL, Life Sciences 67 2000 1325; Christian B et al., Pharm Biochem Behav 78 2004 121]. This is the reason that several of my medical school students at UCSF have started calling Aspartame the "Stupid Sweetener." Since Aspartame contains phenylalanine it should not be used by those with phenylketonuria, but 'Neotame' (also by the Nutrasweet Company owned by Monsato) is the newer version of this sweetener is chemically changed so that phenylalanine can not be broken off the molecule as easily. In a recent "scientific" publication, the Nutrasweet Company stated that “…it is clear that aspartame is safe, and there are no unresolved questions regarding its safety under conditions of intended use.” [Regul Toxicol Pharmacol 35 (2002) S1] While the Nutrisweet Company MAY be correct about aspartame being safe with low levels of consumption, it is certainly NOT true that there are no unresolved questions. Their studies "proving" aspartame's safety are short term studies (a few months or less); no one has looked at long-term use issues. It is therefore my personal opinion that using a half dozen servings of aspartame per day is probably (not definitely) ok, long-term use (several decades of use at that level) is the equivalent of doing new science: You are doing a long-term experiment on yourself, because studies have NOT looked at long-term use. Companies that make low-calorie sweeteners call any 8-week study a "long term study." I would agree if I were only going to eat for the next 8 weeks, but I need health for more than just two months.