Aspartame
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.
Recruitment
Healthy college students.
Design
Counter-balanced, double-blind, within-subject RCT.
Blinding Used
Counter-balanced, double-blind, within-subject.
Intervention
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.
Statistical Analysis
- 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.
Dependent Variables
- Cognitive test (Simple Portable Aviation Relevant Test battery and ANswer-scoring System)
- Plasma phenylalanine levels (plasma blood)
- Alcohol (plasma blood and breath analyzer).
Independent Variables
Aspartame (50mg per kg of body weight).
Control Variables
- 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.
Variables |
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 |
59.08±11.7mcg |
121.5±13.9mcg |
N/A |
P=0.000 |
Blood alcohol |
0% |
N/A |
0.09% |
|
Other Findings
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
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Relevance Questions | |||
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 | |
Validity Questions | |||
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 | |