- Click here for explanation of classification scheme.

To evaluate the relationship between aspartame and brain function, leading to changes in behavior, cognitive function or mood.

• Electronic databases such as Medline, Chemical Abstracts, Science Citation Index, Biosis, Food Science and Technology Abstracts, Agricola, Toxline
• Articles identified from 1970s - 2002
• Published worldwide in peer reviewed journals, with the exception of a few abstracts and book chapters
• Search terms: aspartame, Nutrasweet, aspartic acid, phenylalanine, methanol, diketopiperazine 

Not specifically mentioned.

Recruitment

30+ years of research, over 700 research articles available on aspartame safety.  28 studies used in this section.

Design

Review article.

Blinding used (if applicable)

Some studies used blinding.

Intervention (if applicable)

Aspartame and phenylalanine intake.

Statistical Analysis

Not statistically analyzed.

Timing of Measurements

Testing generally completed before and after aspartame or phenylalanine consumption 

Dependent Variables

• Behavior
• Cognitive Function
• Mood
• All assessed using various tests, specifics are listed under Results

Independent Variables

• Aspartame and/or phenylalanine intake at varying levels and varying time periods, specifics are listed under Results

Control Variables

 

Initial N: 28 studies, subjects per study ranging from 8 - 120 subjects

Attrition (final N):  See above

Age:  All age groups 

Ethnicity:  Not mentioned 

Other relevant demographics:

Anthropometrics

Location:  Worldwide  

 

Other Findings

Studies on Healthy Humans (9 studies):

Intake of aspartame (ranging from 180 mg - 10,080 mg or 15 - 60 mg/kg body wt) or phenylalanine (ranging from 840 mg - 5,040 mg) for 1 day - 1 month resulted in significant increases of plasma phenylalanine concentrations and phenylalanine/large neutral amino acid ratio, but there were no effects on subjective feelings of hunger, mood or arousal, or behavioral tests such as auditory and visual reaction time tasks, Wilkinson auditory vigilance test, Digit Symbol Substitution Test, tapping test, Profile of Mood States, Visual Analogue Mood Scales, 16-item word list, Stanford Sleepiness Scale, EEGs, SPARTANS cognitive battery of aviation-related information processing tasks. 

Studies with Adults Heterozygous for Phenylketonuria (PKUH) (4 studies):

Intake of aspartame ranging from 15 - 45 mg/kg body wt for 12 weeks had no effect on the Amsterdam Neuropsychological Tasks battery including tests for visual information processing and executive function of varying complexity.

Studies with Normal Children (4 studies):

Intake of aspartame ranging from 10 - 34 mg/kg body wt for 1 day - unspecified phase length had no effect on learning, behavior or mood as assessed by associative learning task, an arithmetic test, Children's Depression Inventory, the State Scale of the State-Trait Anxiety Inventory for Children, and several observational measures.  Authors reported decreased minor and gross motor behavior, and increased inappropriate behaviors after sucrose consumption but not aspartame, as well as reduced crying in newborns with both aspartame and sucrose as newborns respond preferentially to sweetness. 

Studies with ADD, ADHD or Sugar-Sensitive Children (6 studies):

Intake of aspartame at 34 mg/kg body wt for 1 day - 2 weeks had no effect on behavior, cognitive function, classroom behavior, noncompliance with adult requests, peer interactions, academic productivity and accuracy, learning or attention span, as assessed by Matching Familiar Figures Test, Children's Checking Task, Airplane Test, Wisconsin Card Sorting Test, Multigrade Inventory for Teachers, Conners Behavior Rating Scale, Subjects Treatment Emergent Symptom Scale.

Studies with Both Normal and Sensitive Children (5 studies):

Intake of aspartame at 32 +/- 8.9 mg/kg body wt - 38 +/- 13 mg/kg body wt for 1 day - 3 weeks had no effect on behavior, activity level, or fine or gross motor coordination, aggressive behaviors, or cognitive function.

 

 

 

This body of literature has included studies conducted with healthy and potentially vulnerable (PKUH) adults and with healthy and potentially vulnerable children, including children with ADD, ADHD, or alleged "sugar sensitivity" or in children with seizure disorders.  Various objective tests, self-rating scales, and naturalistic observations have been utilized in protocols investigating both acute and chronic exposure to high doses of aspartame.  Overall, a considerable body of human research has demonstrated that aspartame has no effect on behavior, cognitive function or mood.

Other:

No funding reported

Key aspects for some studies are discussed, but reader is to assess study quality.  Most studies are short term and do not represent long-term exposure.  Behavior, cognitive function and mood measured in many different ways at varying doses and time periods.  Many of the authors of this review were researchers with included articles.