The World Health Organization’s International Agency for Research on Cancer announced Thursday that the artificial sweetener aspartame, commonly found in Diet Coke and other sugar-free foods, is a possible carcinogen.
However, another WHO group, the Expert Committee on Food Additives, did not change the threshold for the daily amount of aspartame that is safe to consume: 40 milligrams per kilogram of body weight for adults weighing about 154 pounds. Altogether, that’s the amount in around 14 cans of Diet Coke. The Food and Drug Administration has a slightly higher daily limit of 50 milligrams per kilogram of body weight for an adult weighing about 1[ads1]32 pounds.
“It’s a little warning to people, but it’s not ‘do not consume,'” Barry Popkin, professor of nutrition at the University of North Carolina Gillings School of Global Public Health, said of the WHO decision. “Eat moderate levels and you’re OK.”
Aspartame is found in more than 5,000 foods and drinks, and is far sweeter than sugar. In 1974, the FDA approved its use as a tabletop sweetener and ingredient in chewing gum, cereal, instant coffee, dairy products, and other items. Common foods and drinks with aspartame include:
- Tabletop sweeteners including NutraSweet, Equal and Sugar Twin.
- Beverages and drink mixes, such as Diet Coke, Coke Zero, Diet Snapple, Fanta Zero, Sprite Zero, Crystal Light and Wyler’s Light.
- Sugar-free gum, including Trident, Extra, Wrigley’s and Mentos gum.
- Gelatin-based products, including sugar-free Jell-O and Royal Gelatin.
- Syrups, including Mrs. Butterworth’s Sugar Free Syrup and Log Cabin Sugar Free Syrup.
Following the WHO announcement, the FDA said in a statement that it “disagrees with IARC’s conclusion.”
“FDA researchers do not have safety concerns when aspartame is used under the approved conditions,” the agency said.
What the research says about cancer risk and aspartame
The WHO placed aspartame in a risk category below two others: “carcinogenic to humans” and “probably carcinogenic”. Other substances in the “possible carcinogen” category include aloe vera, pickled vegetables and nickel.
Previous research linking aspartame to cancer has not provided conclusive evidence that it causes the disease, and many studies examining links between cancer and artificial sweeteners have relied on animals, not humans, Popkin said.
A 2020 study, for example, found an increased incidence of leukemia and lymphoma in mice consuming aspartame — but the doses were nearly four times the weight of the mice, Popkin said, making them a poor benchmark for human risk. Meanwhile, studies from the 1980s found that aspartame did not cause brain tumors or bladder cancer in rats.
However, a 2022 study of more than 100,000 adults in France found that consuming large amounts of artificial sweeteners was linked to a slightly higher risk of cancer.
Artificial sweeteners can pose other health risks
While the WHO’s announcement may seem to suggest that aspartame is worse than other artificial sweeteners, Popkin said, it could all be linked to negative health effects.
“Honestly, I think it’s such a trivial difference that all dietary sweeteners should be treated the same,” Popkin said. “But if you’re drinking 10 Diet Cokes or 10 Diet Pepsis in a day, you shouldn’t. You need to cut back, because that’s way too much, and it’s moving toward potentially carcinogenic levels.”
Previous research has linked artificial sweeteners to a higher chance of heart disease, high blood pressure, diabetes and obesity.
In May, the WHO advised against consuming artificial sweeteners as a weight loss strategy, as they have not been shown to reduce body fat in the long term.
“If you’re drinking 32 ounces, 64 ounces of soda a day, it’s probably better to have these low-calorie artificial sweeteners than to drink that much added sugar,” said Dariush Mozaffarian, professor of nutrition at Tufts University. “On the other hand, I wouldn’t think of these as just blankets 100% safe. I’d avoid them as much as possible.”
The 2022 study in France found that people who ate aspartame had an increased risk of stroke, and that replacing added sugar with artificial sweeteners did not reduce the risk of heart disease.
In another study published last year, Israeli researchers found that artificial sweeteners changed participants’ populations of gut microbes.
“It’s best to eat a natural, healthy diet with naturally sweet foods,” Mozaffarian said. “So I think of these artificial sweeteners as a bridge away from very high doses of added sugar, but not necessarily a safe switch.”
CORRECTION (July 14, 2023, 5:55 PM ET): An earlier version of this article misinterpreted the WHO’s recommended limit for aspartame consumption. That’s 40 milligrams per kilogram of body weight, not 40 milligrams in total.