SURVEY OF ASPARTAME STUDIES:
CORRELATION OF OUTCOME
AND FUNDING SOURCES
Ralph G. Walton, M.D.
The Center for Behavioral Medicine
Professor and Chairman
Department of Psychiatry
Northeastern Ohio Universities College of Medicine
Please address all correspondence to the author at:
Studies of aspartame in the peer reviewed medical literature were surveyed for funding source and study outcome. Of the 166 studies felt to have relevance for questions of human safety, 74 had Nutrasweet® industry related funding and 92 were independently funded. One hundred percent of the industry funded research attested to aspartame's safety, whereas 92% of the independently funded research identified a problem. A bibliography supplied by the Nutrasweet® Company included many studies of questionable validity and relevance, with multiple instances of the same study being cited up to 6 times. Questions are raised both about aspartame's safety and the broader issue of the appropriateness of industry sponsorship of medical research.
Serious questions have been raised about the reliability of industry sponsored studies of the safety of synthetic chemicals.1 Aspartame, in particular, has been the focus of significant ongoing controversy.2
As early as 1970, eleven years prior to the Food and Drug Administration's (FDA) granting approval for the use of aspartame in dry foods, Olney raised the question of the chemical's potential neurotoxicity. 3,4,5 and recently suggested a linkage to increasing brain tumor rates.6 Wurtman has demonstrated that aspartame can significantly increase brain phenylalanine and tyrosine levels, and can suppress the usual increase in tryptophan that follows a carbohydrate rich meal.7 These neurochemical changes have been linked to numerous adverse clinical events including seizures, 8,9,10 mood disorders, 9, 11,12 headaches, 13 and paradoxical effects on appetite.14
Despite these studies suggesting adverse reactions there is extensive literature attesting to aspartame's safety. Allegations have been made that many of the studies supporting the product's safety have been funded by the Nutrasweet® industry, with consequent questions of appropriateness.15 To date, however, there has been no study correlating outcome with funding source in aspartame related research.
A search of the peer reviewed medical literature, utilizing multiple databases, including Medline, yielded 527 citations on aspartame. Of this number, 165 were felt to have relevance for questions of human safety. The accompanying chart (Table 1) lists these 166 studies, designates the funding source and whether or not an adverse reaction to aspartame was identified.
Seventy-four studies had aspartame related industry sponsorship (Searle, the Nutrasweet® Company, Ajinomoto, or the International Life Sciences Institute Nutrition Foundation) and 91 had non-industry related funding. Some of the studies have multiple funding sources. If an aspartame related industry was one of the sources, the study was considered industry-sponsored.