A study of rats links low doses of aspartame -- the sweetener in NutraSweet, Equal, and thousands of consumer products -- to leukemia and lymphoma.
But food industry officials point out that many other studies have found no link between aspartame and cancer.
The rats in the study were fed various doses of aspartame throughout their lives.
In female but not male rats, lymphoma and leukemia were significantly associated with daily aspartame doses as low as 20 milligrams (mg) per kilogram (kg) of body weight.
To reach a dose of 20 mg/kg, a 140-pound woman would need to drink three cans of diet soda a day.
The sweetener is in thousands of products, ranging from yogurt to over-the-counter medicines.
The study comes from an independent research team led by Morando Soffritti, MD, scientific director of the European Ramazzini Foundation of Oncology and Environmental Sciences in Bologna, Italy.
"What I am recommending is for healthy children and women -- if they do not have diabetes -- to avoid consumer use of aspartame," Soffritti tells WebMD.
A consumer watchdog group, the Center for Science in the Public Interest, has called for FDA action.
If it is accepted as top quality, it could lead to a ban on aspartame," Jacobson tells WebMD.
"I think a lot of companies are going to see the writing on the wall from this study and switch to newer artificial sweeteners.
"So people shouldn't fear that if they have one diet soda a day they are going to develop cancer.
And I must say, the one qualm I have about the study is they found an increased risk of cancer at such a low level of exposure.
If aspartame were that potent a carcinogen, I wonder if we wouldn't be seeing a real epidemic of cancer."