Although this means aspartame might cause cancer in humans, the Group 2B classification from the IARC means the evidence is “limited.” A summary of the working group’s evaluation, also published in The Lancet Oncology, explained that the classification was based on data from three studies assessing the link between aspartame intake and primary liver cancer.
Using that evidence, the World Health Organization and Food and Agriculture Organization Joint Expert Committee on Food Additives confirmed its existing stance that aspartame consumption of up to 40 mg/kg of body weight per day – the amount found in 9-14 diet soft drinks – is safe.
The decision, which was anticipated by Reuters in late June, drew praise from an array of experts who weighed in on the study results via the U.K.-based Science Media Centre. Many emphasized the lack of data showing a causal relationship between the low-calorie artificial sweetener and sought to temper any alarmism related to the decision.
“In short the evidence that aspartame causes primary liver cancer, or any other cancer in humans, is very weak,” said Paul Pharoah, MD, PhD, a professor of cancer epidemiology at Cedars-Sinai Medical Center, Los Angeles. “Group 2B is a very conservative classification in that almost any evidence of carcinogenicity, however flawed, will put a chemical in that category or above.”
Other examples of substances classified as Group 2B are extract of aloe vera, diesel oil, and caffeic acid found in coffee and tea, Dr. Pharoah explained, adding that “this is reflected in the view of the [JECFA] who concluded that there was no convincing evidence from experimental animal or human data that aspartame has adverse effects after ingestion.”
“The general public should not be worried about the risk of cancer associated with a chemical classed as Group 2B by IARC,” he stressed.
Alan Boobis, OBE, PhD, similarly noted that the Group 2B classification “reflects a lack of confidence that the data from experimental animals or from humans is sufficiently convincing to reach a clear conclusion that aspartame is carcinogenic.”
“Hence, exposure at current levels would not be anticipated to have any detrimental effects,” added Dr. Boobis, emeritus professor of toxicology, Imperial College London.
The IARC/JECFA opinion is “very welcome” and “ends the speculation about the safety of aspartame,” added Gunter Kuhnle, Dr. rer. nat., a professor of nutrition and food science at the University of Reading (England).
“It is unfortunate that leaking some information might have created unnecessary uncertainty and concern as consumers might be rightfully worried if they are told that something that is in many foods could cause cancer,” Dr. Kuhnle said. “The published opinion puts this into perspective and makes it very clear that there is no cause for concern when consumed at the current amounts.”
The data reviewed by the IARC Working Group included three studies, comprising four prospective cohorts, that “assessed the association of artificially sweetened beverage consumption with liver cancer risk,” the group reported.
The cohort studies – including one conducted within 10 European countries, one that pooled data from two large U.S. cohorts, and a prospective study also conducted in the United States – each “showed positive associations between artificially sweetened beverage consumption and cancer incidence or cancer mortality” in the overall study population or in relevant subgroups.
Although the studies were of “high quality and controlled for many potential confounders,” the Working Group concluded that “chance, bias, or confounding could not be ruled out with reasonable confidence.” Thus, the evidence for cancer in humans was deemed “limited” for hepatocellular carcinoma and “inadequate” for other cancer types.”
Dr. Pharoah and Dr. Kuhnle disclosed no relevant financial relationships. Dr. Boobis is a member of a number of advisory committees in the public and private sectors, including the International Life Science Institute and The Center for Research on Ingredient Safety at Michigan State University.
A version of this article first appeared on Medscape.com.