The popular diet sweetener aspartame won another round in the safety debate when a European panel of scientists said Friday there's no sign it raises the risk of cancer.
An Italian study last year wrongly concluded the sugar substitute led to higher rates of lymphoma and leukemia in rats, said the experts who advise the European Food Safety Authority.
"There is no reason ... to undertake any further extensive review of the safety of aspartame," said Iona Pratt, a toxicologist who headed the panel.
The findings support a large U.S. federal study released last month, which found no link to cancer in a study of aspartame use among more than half a million Americans.
Aspartame is found in thousands of products, including diet sodas, chewing gum, dairy products and even many medicines. It's sold under the brand names NutraSweet, Equal and Canderel.
The new review of its potential health risks found that the number of tumors in rats did not increase in relation to the dosage of aspartame fed to the animals. Many of the rats in the study had suffered from chronic respiratory disease and the panel said that was the most likely cause of the tumors.
The European panel said its assessment should put the lid on years of debate over the sweetener. The food safety scientists were also satisfied with the current European level set for its safe daily consumption — a maximum of 40 milligrams per kilogram (about 2.2 pounds) of body weight — saying that the limit is well above what people consume normally.
"If you pick up little packets of it, you would have to take 80 of those packets into your coffee in one day in order to exceed this level," Pratt said at a presentation in Rome of the panel's findings.
The Italian researchers who conducted the rat study insisted that their initial findings were correct and pledged to continue studying the subject.
Dr. Morando Soffritti, who led the study for the Bologna-based European Ramazzini Foundation, also assailed the U.S. study, saying that it was an example of how "some researchers are ready to put themselves at the disposal of the industry" that produces sweeteners. He contended the U.S. research didn't distinguish between aspartame and other sweetener use and did not measure lifetime sweetener use.
History is full of examples where animal studies showed benefit or harm from a substance that later proved not true of people. But Soffritti insists that animal studies are better when it comes to aspartame because it's nearly impossible to find a comparison group of people who don't use the sweetener at all.
"How do you do a study on humans when aspartame is used in 6,000 products? How do you find a population that has never used it?" he asked.
Aspartame first came on the market 25 years ago. Research in the 1970s linked a different sweetener, saccharin, to bladder cancer in lab rats. Although the mechanism by which this occurred does not apply to people and no human risk was ever documented, worries about sugar substitutes in general have persisted.
Those concerns grew after Soffritti's research was reported. It involved 1,800 rats and was the largest ever done of aspartame in animals.
The rodents were divided into seven groups and fed different doses of the sweetener over their natural life span. Some of the rats, especially females, developed more lymphomas and leukemias than those not fed aspartame.
But the European food safety panel said the rats had respiratory problems. That and other factors could have affected the observations, the panel said.
The U.S. findings on aspartame are based on lengthy food questionnaires sent in the 1990s to 340,045 men and 226,945 women, ages 50 to 69. They were volunteers in a research project by the National Institutes of Health and AARP, formerly known as the American Association of Retired Persons.
Based on those food surveys, filled out in 1995 and 1996, researchers with the National Cancer Institute calculated how much aspartame the participants consumed, especially from sodas or from adding the sweetener to coffee or tea. No connection was found between aspartame consumption and the type or number of tumors developed in later years.