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Last Updated: Jun 30, 2008 - 11:14:37 AM |
Drinking four to five 20-ounce bottles of diet soda sweetened with aspartame each day may increase risk of cancers such as lymphoma, leukemia and other cancers, suggests an animal study that is scheduled to appear in a March issue of Environmental Health Perspectives, an US government-run environmental science journal.
In the animal study, 1,900 rats were fed the artificial sweetener in feed until they died. After their death, rats were examined to see if they suffered from the special sweet treat.
The results of the study showed that rats fed aspartame-sweetened soda were more likely to develope a variety of cancers, indicating that aspartame is a multipotential carcinogenic agent in rats.
Aspartame, known as Nutra-Sweet or Equal, is widely used in Diet Coke, Diet Pepsi, Diet Snapple and Sugar Free Kool-Aid, according to New York Times. Hundreds of millions of people use such diet soda worldwide.
A group of scientists headed by Dr. Morando Soffritti published their study last year. The news drew criticism from groups such as Calorie Control Council, a trade group for makers of artificial sweeteners that have been trying to quell fears about aspartame in the last 25 years, according to New York Times. Critics say aspartame has been used for so many years and it proved to be safe.
Published in the Nov. 17, 2005 issue of Environmental Health Perspectives, the study found a statistically significant increase in the incidence of malignant tumors, lymphomas and leukemias in rats after exposed to varying doses of aspartame appears to link the artificial sweetener to a high carcinogenicity rate.
The study showed that aspartame's carcinogenic effects are evident at a daily dose of 20 milligrams per kilogram of body weight (mg/kg), notably less than the current acceptable daily intake for humans. Currently, the acceptable daily intake for humans is set at 50 mg/kg in the United States and 40 mg/kg in Europe.
In that study, researchers administered aspartame to Sprague-Dawley rats by adding it to a standard diet. They began studying the rats at 8 weeks of age and continued until the spontaneous death of each rat. Treatment groups received feed that contained concentrations of aspartame at dosages simulating human daily intakes of 5,000, 2,500, 500, 100, 20, and 4 mg/kg body weight. Groups consisted of 100 males and 100 females at each of the three highest dosages and 150 males and 150 females at all lower dosages and controls.
The experiment ended after the death of the last animal at 159 weeks. At spontaneous death, each animal underwent examination for microscopic changes in all organs and tissues, a process different from the aspartame studies conducted 30 years ago and one that was designed to allow aspartame to fully express any carcinogenic potential.
The treated animals showed extensive evidence of malignant cancers including lymphomas, leukemias, and tumors at multiple organ sites in both males and females. The authors speculate the increase in lymphomas and leukemias may be related to one of the metabolites in aspartame, namely methanol, which is metabolized in both rats and humans to formaldehyde. Both methanol and formaldehyde have shown links to lymphomas and leukemias in other long-term experiments by the same authors.
In the current study, aspartame at concentrations of 100,000, 50,000, 10,000, 2,000, 400, 80, or 0 parts per millions (ppm) was administered with feed to 8 week-old Sprague-Dawley rats until they naturally died.
The results of the study have shown for the first time that aspartame causes an increased incidence of malignant tumor-bearing animals with a positive significant trend in males and in females, in particular those females treated at 50,000 ppm.
Aspartame also increased incidence of lymphomas and leukemias in both males and females, in particular in females treated at doses of 100,000, 50,000, 10,000, 2,000, 400 ppm.
Aspartame significantly increased incidence of transitional cell carcinomas of the renal pelvis and ureter and their precursors (dysplasias) in females treated at 100,000, 50,000,10,000, 2,000 and 400 ppm.
In addition, aspartame increased incidence of malignant schwannomas of peripheral nerves in males.
The results indicate that aspartame is a multipotential carcinogenic agent, even at a daily dose of 20 mg/kg body weight, much less than the current acceptable daily intake (ADI).
Previous US studies only observed the study animals to an age equavalent to 53 years old in humans. That is why previous studies would not find any evidence of the carcinogenicity of aspartame.
"Cancer is a disease of the third part of life," Soffritti was quoted by United Press International as saying. "You have 75 percent of cancer diagnoses for people who are 55 years old or older. So if you truncate the experiments at 110 weeks and the rats are supposed to survive until 150 to 160 weeks, it means you avoid the development of cancer at the time when cancer would be starting to arise."
On the basis of these results, the researchers suggest a re-evaluation of the present guidelines on the use and consumption of aspartame is urgent and cannot be delayed.
The current study was funded by the European Ramazzini Foundation of Oncology and Environmental Sciences, a nonprofit organization that studies cancer-causing substances.
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