WHO groups split: Aspartame may cause cancer but still safe to consume

The artificial sweetener aspartame may cause cancer, a World Health Organization-affiliated research group declared Thursday, even as another group linked to the international health body said the sweetener is safe to consume at the currently recommended levels.

The conflicting reports were released from the International Agency for Research on Cancer (IARC), the cancer research agency of the World Health Organization (WHO), and the Joint Expert Committee on Food Additives (JECFA), a group of WHO and U.N. scientists that makes recommendations on how much of a product people can safely consume.

Aspartame is one of the most popular artificial sweeteners in the world, found in many diet sodas like Coke Zero and Diet Coke, some types of sugar-free foods, chewing gum and other products.

“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 and better studies,” Francesco Branca, director of the WHO Department of Nutrition and Food Safety, said in a statement.

According to WHO’s cancer research agency, aspartame is “possibly carcinogenic” to humans and associated with a type of liver cancer called hepatocellular carcinoma, based on limited evidence of three studies.

But those three studies could have been influenced by chance, bias or other flaws.

There are 322 agents included in that classification, which means IARC put aspartame into the same category as engine exhaust, gasoline and infection with type 2 HIV, but also coconut oil soaps, aloe vera, pickled vegetables and nickel.

The separate WHO-affiliated food safety group, meanwhile, concluded that “there was no convincing evidence from experimental animal or human data that aspartame has adverse effects after ingestion.”

The committee said that the data evaluated “indicated no reason to change the previously established acceptable daily intake” of aspartame, which is 40 milligrams per kilogram of body weight per day.

The Food and Drug Administration’s (FDA) recommended daily limit is 50 milligrams of aspartame per kilogram of body weight per day. Based on those guidelines, an occasional can of Diet Coke or chewing gum is unlikely to pose any risk.

The two agencies have different roles in evaluating substances. IARC, the cancer research group, looks at the strength of the scientific evidence of a cancer hazard but not the actual cancer risk. 

Meanwhile the food safety group, JECFA, looks at all possible health impacts and conducts a risk assessment to determine the probability of a specific type of harm. 

A number of public health agencies, including the FDA, have repeatedly said aspartame is safe, and public health experts as well as food and beverage industry executives have expressed concern that the conflicting reports will result in confusion.

On a website for “aspartame and other sweeteners,“ the FDA said aspartame “is one of the most studied food additives in the human food supply” and noted the evidence “has continued to support the FDA’s conclusion that aspartame is safe for the general population when made under good manufacturing practices and used under the approved conditions of use.”

In a letter to the WHO sent in 2022, a top official in the Department of Health and Human Services (HHS) said JECFA was best suited to conduct the review and expressed concern about the concurrent review.

A JECFA assessment considers all relevant toxicological endpoints, including carcinogenicity, wrote Mara Burr, director of the Multilateral Relations Office at HHS. In contrast, an IARC review would be “incomplete and its conclusions confusing to consumers” because it only relies on publicly available data, she wrote.