Stokes AF, Belger A, Banich MT, Bernadine E. Effects of alcohol and chronic aspartame consumption upon performance in aviation relevant cognitive tasks. Aviation, Space and Environmental Medicine. 1994; 65(1): 7-15.PubMed ID: 8117231
To determine whether aspartame has a negative effect on cognitive performance.
Students at the University of Illinois.
- Use of prescription medications or illicit drugs
- Presence of phenylketonuria.
Healthy college students.
Counter-balanced, double-blind, within-subject RCT.
Counter-balanced, double-blind, within-subject.
Subjects received either placebo capsules or aspartame capsules (50mg per kg of body weight per day) for nine days, or an acute dose of ethyl alcohol to achieve 0.1% blood ethanol levels as described earlier. All participants received the placebo and ethanol treatments once and the aspartame treatment twice with a seven-day interval. Blood phenylalanine and breath alcohol levels were measured.
- SPSS used for descriptive statistics comparing subject responses to those of a database of 400 other subjects entered in the SPARTANS (Simple, Portable, Aviation Relevant Test-battery and ANswer-Scoring system) designed to test perceptual-motor abilities, spacial abilities, working memory, attentional performance, risk-taking, reasoning, processing flexibility and planning or sequencing ability
- One-way repeated measures ANOVA on each battery subtask in the SPARTANS battery
- Pairwise comparisons where condition was found to have significant effect on test scores (to determine source of effect)
Timing of Measurements
- Pre-test and post-test administered (no dosing administered)
- At the end of the nine-day dosing period, subjects gave blood that was tested for blood phenylalanine and blood alcohol; they also had a breath analyzer test and were then immediately given a cognitive test battery
- Group One: Pre-test; placebo times nine days; alcohol; aspartame times nine days; aspartame times nine days; post-test
- Group Two: Pre-test; aspartame times nine days; aspartame times nine days; placebo times nine days; alcohol; post-test.
- Cognitive test (Simple Portable Aviation Relevant Test battery and ANswer-scoring System)
- Plasma phenylalanine levels (plasma blood)
- Alcohol (plasma blood and breath analyzer).
Aspartame (50mg per kg of body weight).
- Placebo (negative control)
- Alcohol (positive control)
- Time of day (to guard against effect of circadian rhythm).
- Initial N: 12 (gender not given)
- Attrition: None
- Other relevant demographics: All were University of Illinois students
- Location: Urbana-Champagne, IL.
No deleterious effects of aspartame were detected upon cognitive performance.
After Nine Days of Placebo
After Nine Days of 50mg Aspartame per kg of Body Weight
|After Alcohol Treatment||
Statistical Significance of Group Difference
Blood phenylalanine level
Significant correlation between blood phenylalanine level and higher total score on the Schedule task (R=0.77, P=0.004).
Aspartame caused no detectable cognitive deficits. Ethanol was, however, detrimental to performance.
|Government:||FDA and FAA|
Quality Criteria Checklist: Primary Research
|1.||Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)||Yes|
|2.||Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?||Yes|
|3.||Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?||Yes|
|4.||Is the intervention or procedure feasible? (NA for some epidemiological studies)||Yes|
|1.||Was the research question clearly stated?||Yes|
|1.1.||Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?||Yes|
|1.2.||Was (were) the outcome(s) [dependent variable(s)] clearly indicated?||Yes|
|1.3.||Were the target population and setting specified?||Yes|
|2.||Was the selection of study subjects/patients free from bias?||Yes|
|2.1.||Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?||Yes|
|2.2.||Were criteria applied equally to all study groups?||Yes|
|2.3.||Were health, demographics, and other characteristics of subjects described?||No|
|2.4.||Were the subjects/patients a representative sample of the relevant population?||???|
|3.||Were study groups comparable?||Yes|
|3.1.||Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)||Yes|
|3.2.||Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?||Yes|
|3.3.||Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)||Yes|
|3.4.||If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?||N/A|
|3.5.||If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)||N/A|
|3.6.||If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?||N/A|
|4.||Was method of handling withdrawals described?||Yes|
|4.1.||Were follow-up methods described and the same for all groups?||Yes|
|4.2.||Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)||Yes|
|4.3.||Were all enrolled subjects/patients (in the original sample) accounted for?||Yes|
|4.4.||Were reasons for withdrawals similar across groups?||N/A|
|4.5.||If diagnostic test, was decision to perform reference test not dependent on results of test under study?||N/A|
|5.||Was blinding used to prevent introduction of bias?||Yes|
|5.1.||In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?||Yes|
|5.2.||Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)||Yes|
|5.3.||In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?||N/A|
|5.4.||In case control study, was case definition explicit and case ascertainment not influenced by exposure status?||N/A|
|5.5.||In diagnostic study, were test results blinded to patient history and other test results?||N/A|
|6.||Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?||Yes|
|6.1.||In RCT or other intervention trial, were protocols described for all regimens studied?||Yes|
|6.2.||In observational study, were interventions, study settings, and clinicians/provider described?||Yes|
|6.3.||Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?||Yes|
|6.4.||Was the amount of exposure and, if relevant, subject/patient compliance measured?||Yes|
|6.5.||Were co-interventions (e.g., ancillary treatments, other therapies) described?||N/A|
|6.6.||Were extra or unplanned treatments described?||N/A|
|6.7.||Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?||N/A|
|6.8.||In diagnostic study, were details of test administration and replication sufficient?||N/A|
|7.||Were outcomes clearly defined and the measurements valid and reliable?||Yes|
|7.1.||Were primary and secondary endpoints described and relevant to the question?||Yes|
|7.2.||Were nutrition measures appropriate to question and outcomes of concern?||Yes|
|7.3.||Was the period of follow-up long enough for important outcome(s) to occur?||Yes|
|7.4.||Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?||Yes|
|7.5.||Was the measurement of effect at an appropriate level of precision?||Yes|
|7.6.||Were other factors accounted for (measured) that could affect outcomes?||Yes|
|7.7.||Were the measurements conducted consistently across groups?||Yes|
|8.||Was the statistical analysis appropriate for the study design and type of outcome indicators?||Yes|
|8.1.||Were statistical analyses adequately described and the results reported appropriately?||Yes|
|8.2.||Were correct statistical tests used and assumptions of test not violated?||Yes|
|8.3.||Were statistics reported with levels of significance and/or confidence intervals?||Yes|
|8.4.||Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?||Yes|
|8.5.||Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?||N/A|
|8.6.||Was clinical significance as well as statistical significance reported?||Yes|
|8.7.||If negative findings, was a power calculation reported to address type 2 error?||N/A|
|9.||Are conclusions supported by results with biases and limitations taken into consideration?||Yes|
|9.1.||Is there a discussion of findings?||Yes|
|9.2.||Are biases and study limitations identified and discussed?||Yes|
|10.||Is bias due to study's funding or sponsorship unlikely?||Yes|
|10.1.||Were sources of funding and investigators' affiliations described?||Yes|
|10.2.||Was the study free from apparent conflict of interest?||Yes|