NNNS: Adverse Effects (2011)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • Determine whether individuals who had allegedly experienced urticaria or angioedema after consumption of an aspartame-containing product would demonstrate reactions on challenge with aspartame compared to placebo
  • Describe clinical parameters of reactions that might occur.
Inclusion Criteria:
  • History of urticaria or angioedema within 12 hours of ingestion of an aspartame-containing product during the previous three years
  • History of chronic urticaria, which resolved without medication on cessation of aspartame consumption and recurred when consumption was resumed
  • Positive histamine skin test result
  • Age 10 to 65
  • Informed consent
  • Willingness to remain in a research center for duration of study.
Exclusion Criteria:
  • Pregnancy
  • Dermatographism
  • Homozygous phenylketonuria
  • Confounding medication within three weeks before entry into study
  • Concomitant illness or abnormal laboratory test result interfering with results
  • Aspartame ingestion within three weeks of entry into study
  • Episode of urticaria or angioedema in three weeks before entry into study
  • Employees and family members of employees of The NutraSweet Company.
Description of Study Protocol:


Originally wanted to study 120: 20 at each of six sites:

  • Recruitement letters mailed to 4,700 allergists in US and Canada soliciting patients
  • Advertised in journals
  • Contacted 11 allergy and dermatology societies
  • Contacted 102 people who had filed complaints of urticaria or angioedema allegedly related to aspartame with the NutraSweet Company.


Five-day study, subjects remained in center:

  • Day One: Admission and physical and lab workup
  • Day Two: Ingestion of test material (arm one) described in Intervention below
  • Day Three: Washout
  • Day Four: Ingestion of test material (arm two) described in Intervention below
  • Day Five: Follow-up and discharge.

Blinding Used

All study personnel (statisticians, clinical monitors, study site personnel and database management personnel) remained blind to treatment sequences until the database was complete.


On the test days (days two and four), subjects were given either placebo or aspartame capsules.

Aspartame Capsules

  • Subjects who weighed 40kg or more were given a total of 950mg aspartame in three separate capsules distributed in two-hour increments.
  • Capsule with 50mg aspartame were given at 8:00 a.m., followed by a capsule with 300mg aspartame at 10:00 a.m., followed by a capsule with 600mg aspartame at 12:00 noon. This last dose was accompanied by 7.5mg B-aspartame and 15mg diketopiperazine (DKP). Both of these compounds are present in aspartame-containing products and were included to evaluate the possibility that allergic/hypersensitivity-type reactions could be caused by them rather than by the parent compound.
  • Subjects who weighed less than 40kg were given half the dosage of the above capsules at the 8:00 a.m., 10:00 a.m. and 12:00 noon dosages.

Placebo Capsules

  • The placebo regimen was also administered at 8:00 a.m., 10:00 a.m. and 12:00 p.m. Placebo consisted of identical capsules containing 25mg or 300mg microcyrstalline cellulose.
  • All subjects swished and spit orange juice prior to dosage to mask residual sweetness from aspartame on the capsule and assure maintenance of the blind.

Statistical Analysis

Two-tailed McNemar's test at 5% significance level used to determine the significance of the incidence rates of adverse events after ingestion of aspartame and placebo.

Data Collection Summary:

Timing of Measurements

  • Dosage of intervention as above: 8:00 a.m., 10:00 a.m. and 12:00 noon
  • Vital signs (blood pressure, heart rate, temperature and respiratory rate) determined immediately before ingestion of test material, 15 minutes afterward and at 1:00 p.m., 4:00 p.m. and 8:00 p.m. on challenge days
  • Subjects were monitored at all times for urticaria or angioedema.

Dependent Variables

  • Urticaria: Hives with wheals 4.0mm or more in diameter with a collective diameter of at least 15mm or one or more hives with a wheal of 4.0mm or greater with a flare of 8.0mm or greater
  • Angioedema: Consisted of laryngeal stridor and was diagnosed by a qualified observer using indirect laryngoscopy
  • All reactions were documented by photographs.

Independent Variables

  • Aspartame: 50mg, 300mg and 600mg capsules
  • Placebo: 25mg or 300mg microcrystalline cellulose.
Description of Actual Data Sample:
  • Initial N: 21 (17 female, four male)
  • No Attrition (Final N): 21
  • Age: 10 to 55 years (mean 34±12 years) 
  • Ethnicity: 19 white, two Hispanic


  • Mean height 163.16cm±8.86cm
  • Mean weight 70.38kg±17.72kg.


Six centers in the US:

  • Barnes Hospital and St. Louis Children's, Washington Universiy, St. Louis
  • Children's Hospital/Harvard Medical School, Boston, MA 
  • Northwestern Memorial Hospital, Chicago
  • Ottawa Hospital, Ottawa
  • Center for Health Sciences, UCLA, Los Angeles
  • Duke University, Durham, NC.
Summary of Results:
  • Of the 21 subjects who completed the study, prior to the study ten had experienced urticaria only, ten had experienced both urticaria and angioedema, one had experienced angioedema
  • 17 of the 21 who completed the study had no positive reactions during study
  • Four subjects had urticaria during the study
  • Two of four with urticaria had urticaria after placebo but not aspartame
  • No statistically significant difference in incidence of positive reactions (P=1.000) between aspartame and placebo challenges
  • 10 subjects had a total of 17 other adverse events (throat tightness, light-headedness, warm feeling, dyspnea, nausea, headache, small hives, pruritis, periorbital swelling, nasal congestion, slight tingling of tongue). No statistically significant differences (P=0.289) between aspartame and placebo challenges for adverse experiences.



Author Conclusion:

Aspartame and its conversion products are no more likely than placebo to cause urticaria or angioedema reactions in subjects with a history consistent with hypersensitivity to aspartame.

Funding Source:
Government: NIH
NutraSweet Company
Food Company:
University/Hospital: Harvard Medical School, Duke University Medical Center, Northwestern University Medical School, Washington University School of Medicine, University of California, University of Ottawa Medical School (grants)
Reviewer Comments:
Quality Criteria Checklist: Primary Research
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? ???
  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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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? Yes
  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.) No
  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%.) No
  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.) N/A
  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? N/A
  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? Yes
  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)? N/A
  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? Yes
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? No
  10.2. Was the study free from apparent conflict of interest? Yes