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The World Health Organization muddied the waters on the long-running debate about the safety of the artificial sweetener aspartame by recently labeling it as “possibly carcinogenic to humans.”
The International Agency for Research on Cancer, the cancer agency of the World Health Organization, and the Food and Agriculture Organization Joint Expert Committee on Food Additives in July released an assessment citing “limited evidence” for carcinogenicity in humans but still classifying aspartame as a Class 2B carcinogenic and reaffirming the acceptable daily intake of 40 milligrams per kilogram of body weight (a 154-pound person would have to consume 9 to 14 cans of aspartame-sweetened drinks a day to exceed that limit, according to WHO).
The cancer research agency has a four-level hazard classification indicating the degree of certainty that a substance can cause cancer. With Class 2B classification, there is limited evidence in humans and less than sufficient evidence in experimental animals that a substance causes cancer.
First approved by the U.S. Food and Drug Administration in 1974, aspartame is widely found in various food and beverage products, including diet drinks, dairy products such as yogurt, toothpaste and medications such as cough drops and chewable vitamins.
The assessment from WHO using language that seems to link the artificial sweetener to cancer — a concern that has followed aspartame for years — appears to be a significant change. However, the FDA followed the WHO’s announcement with its own statement saying the agency disagrees with the committees’ conclusions on “one of the most studied food additives in the human food supply.” It pointed out that the committees did not raise safety concerns for aspartame under the current levels of use and did not change the acceptable daily intake.
“FDA scientists do not have safety concerns when aspartame is used under the approved conditions,” according to a statement on the FDA website.
David Turner, Ph.D., recommends using aspartame in moderation. (Photo courtesy Massey Cancer Center)
So what, if anything, changed because of the new assessment? First, it helps to understand how the statement came about, says David Turner, Ph.D., associate professor at the Massey Cancer Center.
The two WHO committees conducted independent but complementary reviews of scientific evidence, including some recent studies pointing to cancer risks, Turner said. The IARC committee concluded there was sufficient evidence to say aspartame is a carcinogen and may cause cancer.
The other committee concluded that, while aspartame may cause cancer, humans are not generally exposed to high enough levels.
Turner, who works in cancer research related to food, says people are generally not exposed to high enough levels of aspartame for it to be a cancer risk but adds that “there is a lot of research that needs to be done to definitively say that.”
One drawback, Turner says, with existing studies is that they often fail to acknowledge subgroups that may be more at risk, such as people who are obese, struggle with chronic conditions or have genetic mutations.
“I pretty much agree with what they are saying but with the caveat that there could be specific groups that might be more susceptible to aspartame and the damage that it does, and you would expect that they might get cancer more readily than other people,” Turner says.
It is difficult to do long-term studies on the effects aspartame has on humans because they involve so many unknowns and are so expensive. Cancer generally occurs over several years and has multiple contributing factors, Turner says. Even long-term studies done with animals consuming the sweetener have produced varying results, he adds.
“One way of putting it is we don’t all just eat aspartame. We eat other things — fats, sugars, whatever it is you eat — that can also affect what happens with aspartame,” Turner says.
Virtually everything with nutrition comes back to the moderation line.
—David Turner, Ph.D., Massey Cancer Center
Cancer is a leading cause of death globally, killing one in six people every year, so “science is continuously expanding to assess the possible initiating or facilitating factors of cancer, in the hope of reducing these numbers and the human toll,” Francesco Branca, director of WHO’s Department of Nutrition and Food Safety, said in an agency statement. “The assessments of aspartame have indicated that, while safety is not a major concern at the doses which are commonly used, potential effects have been described that need to be investigated by more studies.”
Turner says he wishes the committees had specific recommendations to the wider research community on where to go in the future.
For consumers, Turner points out there is often too much ambiguity with nutrition that confuses people.
“Virtually everything with nutrition comes back to the moderation line. If anyone is feeling uncomfortable, there are lots of sweeteners that don’t have aspartame in them, so they can really swap over,” he says. “Anybody that is uncomfortable, it is on the label; you can really avoid them quite easily. But also, definitely don’t have too much of this stuff. That has definitely come out from this study.”
