Prepared by Paul D. Terry (UTGSM Department of Medicine), Ling Zhao (UT Department of Nutrition), and Jiangang Chen (UT Department of Public Health)
Aspartame is an artificial sweetener that is added to many foods, candies, gums, and beverages, such as diet soda. Because it is approximately 200 times sweeter than table sugar, smaller amounts of aspartame are added to foods, with considerably fewer calories. NutraSweet® and Equal® are well-known brand names
for aspartame sold in packages for individual use. Since aspartame was first approved for consumer use in the 1970s, scientists have expressed some concerns regarding its safety. To date, however, there has been no clear evidence of harm. Nonetheless, because scientific studies of aspartame consumption continue to be conducted and published, the evaluation of potential risk is an ongoing process. The recent designation of aspartame as “possibly carcinogenic” by IARC is based on “limited” evidence. IARC classifies degrees of evidence of carcinogenicity as being “sufficient,” “limited,” “inadequate,” or “suggesting lack of carcinogenicity.” “Limited” evidence, such as it pertains to aspartame in this instance, denotes weak or inconsistent associations or evidence that cannot be considered “sufficient” due to an appreciable potential for bias. In other words, some data suggest an association between aspartame consumption and the risk of hepatocellular cancer, but those data are methodologically too weak to be definitive.
Independently of the IARC expert panel, WHO also collaborates with the Food and Agriculture Organization Joint Expert Committee on Food Additives (JECFA), which currently concludes: “There is no convincing evidence from experimental or human data that aspartame has adverse effects after ingestion, within the limits established by previous committee [members],” which is 40 mg/kg of body weight in aspartame per day. This translates to approximately 8 to 12 cans of soda for a person weighing 132 lb. (60 kg) and 2 to 3 cans per day for a child weighing 33 lb. (15 kg), depending on the amount of aspartame in the drink, the exact weight of the consumer, and assuming no additional aspartame is ingested from other sources. Thus, two separate WHO-sponsored expert panels appear to be reaching different conclusions regarding the potential risk posed by aspartame.
How Can Two WHO-Affiliated Consensus Groups Reach Different Conclusions?
It is not uncommon for scientific consensus groups to differ in how they classify risk based on the results of published studies, even if more than one of those consensus groups is affiliated with the same agency or parent organization. For example, there may be differences in the criteria used to define specific risk categories, the reliance on animal and in vitro studies with unclear applicability to humans, the human studies that are selected for review and analysis, how individual study results are weighted in terms of quality and limitations when forming conclusions, which specific disease endpoints are being considered, the timing of review panel meetings (calendar month and year) relative to when the most recent studies were published, and even the degree to which individual panel members are experienced and dispassionate with respect to the subject under review.
IARC’s statement may appear to be more worrisome than that of the JECFA, but the two statements are not incompatible. IARC’s classification of “limited” denotes a relatively weak degree of evidence. Thus, JECFA’s “no convincing evidence” is consistent with IARC’s classification. Furthermore, in terms of chemical safety evaluation, IARC assesses whether a chemical substance could potentially induce or promote the development of cancer, whereas JECFA assesses the likelihood of harm at specific levels of exposure. Because “evidence suggesting lack of carcinogenicity” does not exist for every substance that is safe with normal use, the JECFA’s recommendation is more relevant in establishing public health guidelines. It is not surprising, therefore, that WHO continues to support JECFA’s recommendation of a daily maximum aspartame intake of 40 mg/kg of body weight, or approximately 60 packets of aspartame per day for a person weighing 132 lb. (60 kg). Of note, JECFA’s recommendation is more conservative than the U.S. Food and Drug Administration’s (FDA) recommended maximum daily intake of 50 mg/kg, or approximately 75 packets of aspartame per day for a person weighing 132 lb. The current position of both the FDA and the European Food Safety Authority (EFSA) is that the consumption of properly manufactured aspartame at typical exposure levels is safe.
Is Aspartame Less Safe Than Other Sweeteners?
Alternatives to aspartame include other artificial sweeteners (such as saccharin and sucralose), sugar alcohols (such as sorbitol and xylitol), naturally-derived sugar-free sweeteners (such as Stevia), and natural, simple sugars, such as those in sugar cane, sugar beets, and honey. The availability of a wide variety of approved sweeteners seems like a good thing, but a typical internet search reveals considerable inconsistency in how different organizations and individuals rank these sweeteners in terms of consumer health. For example, whereas some view cane sugar as preferable for being more natural and containing more nutrients, others argue that simple sugars are addictive, diabetogenic, and nutritionally insignificant; whereas some view artificial sweeteners as a viable means to avoid sugar, others suggest that the potential harms of artificial sweeteners are still not sufficiently understood; and whereas some view Stevia or sugar alcohols as a good compromise between artificial sweeteners and simple sugar, others advocate abstinence from any sweetener product. Depending on the direction and breadth of one’s search for information, the consumer may be left with little more than conflicting cautions and recommendations.
What is the “Bottom Line” Regarding Aspartame?
Regarding the choice and use of sweeteners, consumers may wish to consider such things as taste preference, body weight and composition, diabetes status and risk, possible allergic responses to a sweetener (such as headaches), and evidence from future scientific studies. For some individuals, such considerations are preferably taken in consultation with their physicians. Regarding aspartame, several national and international consensus groups have evaluated dose-risk associations with human health and consider typical levels of consumption to be safe. Indeed, after many years of laboratory and epidemiologic studies, there remains no clear evidence that consumption of aspartame in typical doses presents any significant risk.