A study reported last week renewed the debate over the safety of aspartame, one of the world's most popular artificial sweeteners. The study, conducted by researchers at the European Ramazzini Foundation of Oncology and Environmental Sciences in Bologna, Italy, found that aspartame causes lymphomas and leukemias in rats. Lymphomas are malignant tumors of the lymph glands, whereas leukemias are malignancies of bone marrow. The study noted no statistical increase in brain tumors, one of the most widely cited concerns about aspartame.
The Italian researchers studied 1,800 rats for nearly three years. The doses of aspartame (the study used the American brand NutraSweet) were provided in a ratio equivalent to human intake. "The data indicate that [aspartame] causes a statistically significant increase in the incidence of lymphomas and leukemias in females. ... This increase is dose-related," the researchers wrote.
The research "is not consistent with the extensive body of scientific research [that] exists on aspartame," according to Ajinomoto, one of the largest manufacturers of aspartame, based in Tokyo. Citing its safe use by "hundreds of millions of consumers around the world" since 1979, Ajinomoto said the sweetener is made of two amino acids, the building blocks of protein. "Even frequent users of products with aspartame obtain about 99 percent of their daily dietary intake of the two amino acids in aspartame from other dietary sources." The company also criticized Ramazzini's research methods, stating that the U.S. Food and Drug Administration found the foundation's previous work to be unreliable. In addition, Ajinomoto said, the researchers have not responded to requests to submit their work for peer review.
According to the Ramazzini scientists, however, the studies Ajinomoto cites, performed in the 1970s, "did not comply with the basic requirements which must nowadays be met when testing the carcinogenicity potential of a chemical or physical agent." Moreover, they say aspartame is metabolized into not two, but three components: the amino acids aspartic acid and phenylalanine, and methanol. "The increase in lymphomas and leukemias, observed in the [aspartame] study, could be related to methanol, a metabolite of [aspartame], which is metabolized to formaldehyde and then to formic acid, both in humans and rats." The researchers further note that in 2002, methanol administered to rats in drinking water increased the rates of these same types of cancer.
Aspartame is used in more than 6,000 products worldwide. In the United States and Europe, the maximum recommended intake is 40 mg to 50 mg per kg of body weight. An adult would have to drink 14 cans of an aspartame-sweetened soda to consume that much.
The European Food Safety Authority has said it will review the findings "as a matter of high priority" and that the review would likely take several months. An FDA official said the agency was aware of the publication of preliminary data but had not yet reviewed it. "We will be requesting primary data from the study for our review. The extensive information which we have previously reviewed supports the safety of aspartame for use in a normal diet," the official said.
NutraSweet, the largest American manufacturer of aspartame, did not return a phone call seeking comment. NutraSweet was first formulated in 1965 at G.D. Searle Co. In 1981, aspartame was approved for use in dry goods, some say at the behest of Donald Rumsfeld, then CEO of Searle and a member of Ronald Reagan's transition team. It was Rumsfeld who appointed the FDA commissioner. FDA had denied approval until that time. In 1985 Monsanto acquired Searle, and sold it in 2000 to equity firm J.W. Childs for $440 million.