Aspartame – an artificial sweetener found in diet sodas, gum, and other foods – has been ruled a possible cause of cancer by the World Health Organization.

WHO officials say the sweetener is still considered safe in limited quantities, but called for “a bit of moderation.”

Current guidelines set the ‘acceptable daily intake’ at 40 milligrams per kilogram of body weight.  For a 150-pound person, that’s roughly 12-14 cans of diet soda per day.