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Evaluation of Consumer Complaints Related to Aspartame Use

In February 1984, the U.S. Food and Drug Administration (FDA) requested CDC's assistance in evaluating consumer complaints that FDA had received about consumption of aspartame-containing products. The request followed an increase in aspartame-related complaints in the latter half of 1983. Complaints to the FDA increased from 108 in the first 6 months of 1983 to 248 in the last 6 months. This increase coincided with approval of aspartame for use in soft drinks in July 1983.

The CDC investigation had two major purposes: (1) to provide a basic descriptive analysis of the symptoms reported and the epidemiologic characteristics of the persons reporting those symptoms; and (2) to determine whether specific individual symptoms or constellations of symptoms were reported with enough consistency to indicate where further clinical studies, should they seem necessary, would be most productive. It was recognized from the outset that this investigation alone would be unlikely to establish any cause-and-effect relationship between the ingestion of aspartame and the occurrence of reported symptoms. Application of criteria

The quality and type of evidence that may be obtained by a passive surveillance system does not allow definitive determination of whether given symptoms are or are not caused by the agent under question--in this case, aspartame. Passive surveillance implies that cases or reports are not actively solicited by the agency or organization concerned but, rather, are initiated on the part of the consumer or complainant. In such a passive surveillance system, serious problems may be more likely to be reported, even if they occur less often than mild problems. Problems occurring soon after use of a product are more likely to be thought to be caused by the product and, hence, reported. Thus, passive surveillance systems are more likely to detect rare and serious conditions and symptoms occurring shortly after use of a product than common symptoms or symptoms occurring at some longer period after product use. However, symptoms that are common in the general populace and are reported in a passive surveillance system are more likely to have occurred by chance in association with use of the product than are more rare symptoms.

Criteria originally developed to assess potential adverse reactions to medications were adapted to evaluate the likelihood that symptoms reported by individuals through this passive surveillance system could be due to aspartame consumption (1,2). However, application of these criteria was limited by a number of factors. For example, when evaluating reactions to medications, physician reports indicating concurrent illness and use of other medications are usually available. In the case of aspartame use, because few of the complainants sought medical aid, few physician reports containing information specific to the aspartame complaints were available. For this reason, information about other potential causes of symptoms, such as concurrent illnesses or medications, was often limited. Moreover, details relating to the time between ingestion of aspartame and onset of symptoms often were incomplete because aspartame consumption was part of the daily routine.

From the clinical studies performed before FDA approval of aspartame, there was little to suggest that acute reactions would be likely to occur. Therefore, no defined symptom constellation could be specifically sought in reinterviewing complainants. As far as is known, complaints, such as those reported in this analysis as being related to aspartame use, have not been commonly reported in other countries in which aspartame is also in use.

An important criterion in assessing potential adverse reactions is the consistency of reported symptoms with rechallenge, i.e., the recurrence of symptoms after consuming aspartame-containing products a second time. Even the application of this criterion has substantial limitations. People who experience symptoms once may be primed to experience them on repeated use. Conversely, persons with particularly serious or unpleasant complaints would be unlikely to use aspartame again, and, therefore, there would be no information on the effects of rechallenge.

Evaluation of dose-response relationships might have been fruitful had individuals reported symptoms with increasingly high consumption of aspartame-containing products. However, due to the difficulties in quantifying intake from the available data, evaluation of dose-response relationships was not possible. General Findings

In carrying out this analysis, attempts were made to interview in depth all complainants who had reported problems before mid-April 1984 to the FDA; to G. D. Searle and Company, the manufacturer of aspartame; to the Arizona Department of Health Services; to Dr. Woodrow C. Monte, Director, Food Science and Nutrition Laboratory, Arizona State University; and to Mr. James C. Turner, Counselor, Community Nutrition Institute, Washington, D.C. Of 592 complaints received by these combined sources, CDC was able to interview 517 (87%).

By June 15, 1984, the date on which the CDC analysis began, 231 (45%) of the interviews had been completely coded and reviewed. These cases were analyzed in depth. The remaining 286 case interviews subsequently submitted to CDC were reviewed for demographic characteristics and symptom category to assure that their exclusion from the in-depth analysis would be unlikely to bias the findings. The demographic characteristics and symptom categories of the two groups were similar. Although some fairly minor differences were found between the two groups, such as state of residence and date of report, these differences were not felt to be substantial enough to affect the overall conclusions.

Overall, the 517 interviewed complainants were predominantly white (96%), female (76%), and between the ages of 21 and 60 years (79%). Complainants were approximately 1.5 times more likely to be female and 2.5 times more likely to be women between the ages of 20 and 59 than expected from 1980 census estimates. Reports came from all geographic regions of the country, with a heavy concentration of cases from Arizona, where the possibility of aspartame use leading to illness received particularly extensive press coverage. Although aspartame-containing products are widely distributed in the United States and are likely to be consumed by millions of users, there is no specific marketing information available as to who were likely users and/or what groups were most likely to consume the largest per-capita amounts of aspartame. Thus, CDC is unable to estimate a specific complaint rate in relation to the actual number of users.

Many complainants reported a variety of symptoms involving several organ systems. Overall, 346 (67%) complainants reported neurological/behavioral symptoms, including headaches, dizziness, and mood alterations. One hundred twenty-four (24%) reported experiencing gastrointestinal symptoms, and 76 (15%) reported allergic type and/or dermatologic symptoms. Thirty-two women (6% of case reports) reported alterations in their usual menstrual patterns. Forty-seven (9%) reported other symptoms of various types. Because persons often reported symptoms from more than one category, the total number of symptoms reported was greater than the actual number of complainants.

Overall, of the 231 complaints analyzed in depth, 13% reported that symptoms recurred after rechallenge with more than one product, and another 15% reported that symptoms recurred on second use of the same product. One physician, anecdotally, has reported on a child who underwent a double-blind trial, which, by verbal report, supported the patient's history of hyperactivity following consumption of aspartame. Conclusions

This investigation of consumer complaints of symptoms experienced after consumption of aspartame-containing products identified no specific constellation of symptoms clearly related to aspartame consumption. The overrepresentation of women reporting symptoms could not be explained with available data. Despite great variety overall, the majority of frequently reported symptoms were mild and are symptoms that are common in the general populace. While some reports are undoubtedly due to the coincidence of symptoms and aspartame consumption, and others may be due to the suggestibility of some persons, still others may be attributable to some as yet undefined sensitivity of some individuals to aspartame in commonly consumed amounts. The only way these possibilities can be thoroughly evaluated would be through focused clinical studies.

In summary, currently available information, based on data with limitations as described in the report, indicates a wide variety of complaints that are generally of a mild nature. Although it may be that certain individuals have an unusual sensitivity to the product, these data do not provide evidence for the existence of serious, widespread, adverse health consequences attendant to the use of aspartame. Reported by Div of Nutrition, Center for Health Promotion and Education, CDC.


  1. Kramer MS, Leventhal JM, Hutchinson TA, Feinstein AR. An algorithm for the operational assessment of adverse drug

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