WHO agency warns of potential cancer risk from aspartame

For the new report, IARC convened 25 cancer experts from 12 countries to review existing research on cancer risk. Overall, the researchers determined that there was "limited evidence" that aspartame was "possibly carcinogenic to humans."

According to IARC's working group, several recent studies found an association between consuming artificially sweetened beverages and certain kinds of liver cancers. Three studies also found an increased incidence of liver cancer in both mice and rats after consuming aspartame.

However, Mary Schubauer-Berigan, acting head of IARC's monographs program, noted that the experts' findings only identified aspartame as a potential carcinogenic hazard and did not assess its potential risk of causing cancer in humans.

"A hazard identification aims to identify the specific properties of the agent and its potential to cause harm — that is, the potential of an agent to cause cancer," she said. "The classification reflects the strength of the scientific evidence as to whether an agent can cause cancer in humans, but it does not reflect the risk of developing cancer at a given exposure level."

IARC also noted that it could not rule out chance, bias, or confounding as potential explanations for its findings.

In a separate report released at the same time, WHO's Joint Expert Committee on Food Additives (JECFA) determined that the available evidence on aspartame and cancer risk was inconclusive. Based on these findings, JECFA did not change its current recommended maximum daily dose of aspartame, which is set at 40 milligrams per kilogram of a person's weight.

According to Francesco Branca, WHO's director of nutrition and food safety, this limit is roughly equivalent to nine to 14 cans of soda a day for an average-sized adult weighing 70kg (154lb). For young children, the limit would be lower at roughly 800 mg of aspartame, or two to three cans of soda a day.

In general, "[o]ccasional consumption of aspartame is … probably not going to be associated with a health risk for most individuals," Branca said.

Commentary

Reactions to WHO's reports have largely been mixed, with some experts saying that aspartame is largely safe while others argue there are still potential concerns about its health risks and that more research is needed.

In response to IARC's report, FDA said it disagreed with the conclusion that aspartame should be classified as a possible carcinogen to humans. The agency also noted that there were "significant shortcomings" in the studies that IARC used in its analysis.

"Aspartame is one of the most studied food additives in the human food supply," the agency said. "FDA scientists do not have safety concerns when aspartame is used under the approved conditions."

Food industry leaders have also pushed back on IARC's findings, arguing that several food safety agencies and more than 90 countries have found aspartame to be safe.

"That is an expression of personal opinion, not the science," said Kevin Keane, interim president of the American Beverage Association. "The compendium of science consistently shows all these products are safe and can be part of a balanced diet. We offer people an array of safe beverage choices that can meet their needs, including if they want to reduce sugar and calories."

However, other health experts disagreed. According to Thomas Galligan, principal scientist for food additives and supplements at the Center for Science in the Public Interest (CSPI), IARC's conclusion about aspartame being a potential carcinogen is "pretty much in line with what CSPI has been saying for years" and "really reemphasizes the need for consumers to avoid aspartame."

"We would like to see the FDA protect consumers by banning aspartame," Galligan said. "We strongly hope that the FDA will take notice and re-evaluate, and even though they've said many times that aspartame is safe, we hope they'll take the WHO's evaluation very seriously."

In general, many health experts say that there is not enough long-term research into aspartame, which is important since it can take decades for cancer to develop after carcinogen exposure. WHO officials have also said they hope the reports will lead to more research into the potential risks of aspartame.

"This is really more a call to the research community to try to better clarify and understand the carcinogenic hazard that may or may not be posed by aspartame consumption," Schubauer-Berigan said. (Florko, STAT, 7/13; Reiley, Washington Post, 7/13; Jewett, New York Times, 7/13; Mallenbaum, Axios, 7/13; Frieden, MedPage Today, 7/14; Weintraub, USA Today, 7/14; Aubrey, "Shots," NPR, 7/13)

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