On Thursday, the World Health Organization classified the soda sweetener aspartame as a possible carcinogen and cancer link but said it is safe for people to consume within limits.
By some calculations from another WHO panel, a person weighing 150 pounds could avoid a risk of cancer but still drink about a dozen cans of diet soda per day.
Aspartame is a nearly ubiquitous artificial sweetener, though has been a contentious ingredient for decades.
The International Agency for Research on Cancer said it based its conclusion on limited evidence from three observational studies of humans. The agency said these studies linked consumption of artificially sweetened beverages to an increase in cases of liver cancer at levels far below a dozen cans a day. It called for further study and cautioned that the results could potentially be skewed toward high-volume drinkers.
The U.S. Food and Drug Administration, which approved aspartame decades ago, issued an unusual criticism of the WHO’s findings and reiterated its position that the sweetener is safe. The FDA said it “disagrees with I.A.R.C.’s conclusion that these studies support classifying aspartame as a possible carcinogen to humans.”
Aspartame is used in Diet Coke, Pepsi Zero Sugar and other diet sodas, as well as some chewing gum and various Snapple drinks as a sugar substitute.
