Artificial sweetener aspartame is possibly carcinogenic, WHO says

More research is needed, WHO officials said, to better understand the sweetener’s risks. While safety is not a “major concern” at the levels people typically consume aspartame, “potential effects have been described that need to be investigated by more and better studies,” Dr. Francesco Branca, director of the WHO’s nutrition and food safety department, said in a statement.  

The Calorie Control Council, a trade group for the low-calorie food and beverage industry, says on its aspartame website that scientific evidence “overwhelmingly supports the safety of aspartame even in amounts far greater than people typically consume,” adding that over 200 studies attest to its safety. Following earlier press reports that the cancer-research agency’s classification of aspartame was forthcoming, the International Council of Beverages Associations said in a statement that the designation “contradicts decades of high-quality scientific evidence” and that it remains “confident in the safety of aspartame” given positive determinations from food safety authorities in more than 90 countries.

Read more: What is aspartame, and is it bad for you? Here’s what health experts say

Aspartame, sold under brand names like Equal and NutraSweet, was approved as a sweetener by the U.S. Food and Drug Administration in 1974. 

The new assessments come in the wake of WHO guidelines released in May recommending against the use of non-sugar sweeteners to control body weight. The available evidence suggests that use of non-sugar sweeteners “does not confer any long-term benefit in reducing body fat in adults or children,” the WHO said, and long-term use may have negative effects such as higher risk of type 2 diabetes and cardiovascular diseases. 

If consumers are trying to decide between drinks containing sugar and those with artificial sweeteners, “I think there should be a third option considered, which is to drink water instead, and to limit the consumption of sweetened products altogether,” Branca said during a press briefing Wednesday. “This is particularly important for young children,” he said, who can adjust their tastes early on. 

The WHO cancer-research agency’s designation of aspartame as “possibly carcinogenic to humans” places the sweetener in the third-highest out of four classification levels assessing the strength of evidence as to whether an agent can cause cancer. Other agents with the same classification include aloe vera, chloroform and gasoline-engine exhaust.

Those classifications consider all types of exposures — whether it’s through diet, occupational, or other means — and they don’t illustrate the risk of developing cancer at any particular exposure level. A WHO and Food and Agriculture Organization joint committee of experts on food additives assesses risks based on levels of exposure, and that group reaffirmed Thursday evening that it’s safe to consume up to 40 milligrams of aspartame per kilogram (or 2.2 pounds) of body weight daily. 

That adds up to a lot of diet sodas: A person weighing 154 pounds would have to drink more than nine to 14 cans per day to exceed that level, assuming there’s 200 to 300 milligrams of aspartame in each drink, according to the committee. The FDA says the acceptable daily intake of aspartame is even higher, at 50 milligrams per kilogram of body weight.

After weighing animal and human studies, the food additives expert committee “concluded that the evidence of an association between aspartame consumption and cancer in humans is not convincing,” Dr. Moez Sanaa, head of the WHO’s standards and scientific advice on food and nutrition unit, said in a statement. “We need better studies with longer follow-up” and repeated dietary questionnaires, he said. 

The evidence that triggered the cancer-research agency’s “possibly carcinogenic” designation for aspartame comes from three studies of artificially sweetened beverages conducted in the U.S. and 10 European countries, Dr. Mary Schubauer-Berigan, acting head of the International Agency for Research on Cancer’s monographs program, said during the press briefing Wednesday. The group determined that the artificially sweetened beverage consumption studied was a good proxy for aspartame consumption, given that aspartame was the main sweetener used in those drinks in the times and places studied, Schubauer-Berigan said. All three studies showed links between the beverage consumption and liver cancer. But the group determined that chance and bias could not be ruled out, she said, leading to the conclusion that the evidence is limited. 

Both the cancer-research agency and the food additives committee based their assessments on scientific data from peer-reviewed papers, government reports, regulatory studies and other sources.