The Italian scientist Morando Soffritti has revived the debate about the safety of aspartame, an artificial sweetener used in many popular products, including diet softdrinks made by Coca-Cola and Pepsi Co. After studying 1,800 rats over eight years, his research team concluded that aspartame could have carcinogenic effects.

The results, first released in July 2005 and published in March in the U.S. Department of Health's journal, "Environmental Health Perspectives", contradict other studies financed by the company that created the sweetner, G.D. Searle & Company, which assures aspartame poses no risks to human health.

For the past 25 years, the product has been authorised by the U.S. Food and Drug Administration (FDA) for human consumption.

The sale of aspartame, with only four calories per gram and 200 times sweeter than sugar, is sold under the trademarks NutraSweet and Equal, bringing in 570 million dollars a year. It is estimated that some 350 million people around the world, many in hopes of losing weight, consume aspartame daily through 6,000 kinds of foods and beverages. In Europe alone, 2,000 tonnes of the sweetener are sold annually.

Soffritti's investigation was conducted at the Cesare Maltoni Cancer Research Centre, of the European Ramazzini Foundation in Bologna, which he heads. This institution, founded in 1971, won international credibility when it uncovered the cancer-causing properties of the gasoline additive MTBE (methyl tertiary butyl ether), which led to its ban in 21 U.S. states.

Tierramérica spoke with Soffritti in Italy. Following are excerpts from that dialogue:

Q: What are the results of your investigations conducted between 1997 and 2005 about the effect of aspartame?

A: The results indicate that aspartame is a multi-potential carcinogen, even consumed daily at 20 milligrams per kilogram of body weight. That is a lower quantity than the maximum recommended by the FDA (50 mg/kg of body weight) and the European Union (40 mg/kg).

Q: What kind of cancer does it produce?

A: Our study showed for the first time that aspartame increases the incidence of malignant tumours in rats. In the females it increases leukaemia and lymphomas, as well as cancerous cells in the pelvis and urethra. In the males, it especially increases the incidence of malignant tumours in peripheral nerves.

Q: How many rats were studied and what method was used?

A: We studied 1,800 rats (Sprague-Dawley) that were raised for this purpose. We gave them, by groups, doses similar to those ingested daily by people, of 5,000, 2,500, 500, 100, 20, 4 or 0 mg/kg of body weight. Aspartame was added to the standard diet (seven doses in the food).
The experiment began when the animals were eight months old and lasted until their natural death, at 159 weeks. When the rats died we conducted histopathological studies of their organs and tissues. We analysed more than 30,000 samples.

Q: Can it be assumed that what happened in the rats could also happen in human beings?

A: According to an investigation of cancer by the World Heath Organisation, the experimental study of carcinogenic agents in rats is very important for humans. One-third of the cancer-causing agents in man have been discovered with experiments conducted on animals.

Q: Aspartame is sold mainly as a means for people to control their weight. In your experiment, did the animals lose weight?

A: No. We saw that those consuming aspartame ate less, but their body weight remained the same. We don't have an explanation for that, not in our field.

Q: Aspartame is also consumed by children and by pregnant women. What effects could it have on them?

A: The study of the doses correlated between the milligrams that were consumed and body weight. This tells us that the carcinogenic effect in children could be greater (because of their lower weight). The carcinogenic agents have a stronger effect on the embryo, which is why pregnant women are at greater risk.

Q: Are people who consume aspartame condemned to developing cancer?

A: Cancer is related to many factors and to genetics. We can't say that a consumer of aspartame will develop cancer. There are people who smoke cigarettes their entire lives and never develop lung cancer.

Q: There are several studies that assure aspartame is harmless to human health. What is the difference between those and the study that you led?

A: First, those studies about the cancerous effect in rats and mice were done in the 1970s, before the commercialisation of aspartame began, and were paid for by the companies that produced [the sweetener].
The results of those studies did not show that aspartame was carcinogenic. But some members of the scientific community doubt the quality of of those experiments because some animals that consumed aspartame presented with brain tumours, while the control animals didn't have any problems.
Second, those studies utilised fewer animals (280 and 688 rats) and were not conducted according to the standards of "Good Laboratory Practices", so one cannot conclude with certainty that aspartame is not a carcinogen. Our research centre is independent. It doesn't receive any financing from the industry producing the product.

Q: Are new scientific studies about the potential cancer-causing effects of aspartame necessary?

A: Yes, more studies are needed in order to obtain greater precision in quantifying the risk. The current results already demand -- by the competent bodies -- an urgent review of the norms regulating the use and consumption of aspartame in order to protect public health, especially children's health.

Q: Your study is being reviewed by the European Commission's Food Safety Authority, which will issue a statement in May. Do you think it will validate your study, and do you think government agencies in Europe and elsewhere should ban aspartame?

A: I hope they revise their current regulations.

•  More articles on Aspartame