Study Linking Aspartame to Malignant Tumors, Leukemia, and Lymphomas Even at Low Consumption Levels Rekindles Safety Debate

By Steven DiJoseph

From the very beginning, aspartame has been mired in controversy with respect to potential long-term health problems associated with its use as an artificial sweetener in thousands of food products worldwide.

Highly debatable safety studies by its inventor, G. D. Searle & Co., allegations of dubious conduct on the part of the company and FDA officials during the approval process, and the marked discrepancy between industry-funded studies (100% favorable) and independent analyses (91% negative to one degree or another), have fueled an ongoing, contentious dispute between supporters and critics of the sweetener. (For a thorough examination of these factors, see “The Lowdown on Sweet?” by Melanie Warner, The New York Times 2/12/06.)

An Italian study that was released last July ( 7/15/05) only promises to harden the battle lines on each side of the debate and renew calls for a ban on the use of aspartame in all food products. The study has already prompted numerous countries and their respective health agencies to re-examine (or examine for the first time) the safety of aspartame as an artificial sweetener.

Aspartame is a highly successful artificial sweetener invented in 1965 that is 200 times sweeter than ordinary sugar. Although it has enjoyed growing success in the U.S., the UK, and other markets over the past 10 years, it has also been the subject of claims that it is linked to various forms of cancer.

The sweetener, marketed under the brand names NutraSweet and Equal, is found in a number of low-calorie or non-calorie drinks and foods. It is also packaged and sold in powder or tablet form as a sweetener for cold or hot beverages or for the use in food or baking recipes.

The manufacturer, NutraSweet AG, has always maintained that the overwhelming weight of scientific evidence does not link the product to malignant brain tumors or any other form of cancer. The company regards efforts to label the sweetener as a health risk as nothing more than “scare-mongering.”

Thus, the company welcomed the announcement of an upcoming three-year study by researchers from King’s College (London) which will examine whether there is any link between the product and an increased risk of developing malignant brain tumors.

Among other things, the researchers will look at whether people with certain genetic make-ups are susceptible to methanol, a component of aspartame, which some research has suggested may attack DNA and cause cells to mutate and cause cancer.

While that study is still far off in terms of meaningful data, the Italian study involving rats, published first in the European Journal of Clinical Oncology, and then in Environmental Health Perspectives (EHP) has demonstrated far more than mere suspicion of a link between aspartame and cancer.

The EHP-in-Press peer-reviewed article is published under the title: First Experimental Demonstration of the Multipotential Carcinogenic Effects of Aspartame Administered in the Feed to Sprague-Dawley Rats ( Its authors are Morando Soffritti, Fiorella Belpoggi, Davide Degli Esposti, Luca Lambertini, Eva Tibaldi, and Anna Rigano.

Dr. Soffritti is a renowned expert with 28 years of experience researching potential carcinogens who oversees some 180 researchers in 30 countries.

In the study conducted at the Cancer Research Center in Bologna, eight-week-old rats were fed varying amounts of aspartame while the control group remained free of the product. The results were disturbing in that these rats,showed significant evidence of cancers, including leukemia, lymphomas, and tumors in multiple organs.

Aspartame is found in more than 6,000 products, including carbonated and powdered soft drinks, candy, desserts, hot chocolate, chewing gum, yogurt and tabletop sweeteners, as well as some pharmaceutical products like vitamins and sugar-free cough drops. It is the second most widely used artificial sweetener in the world.

Over 200 million people worldwide consume the sweetener. First approved by the FDA in 1974, aspartame has been used for more than 30 years.

The acceptable daily intake for humans is currently 50 mg/kg in the United States and 40 mg/kg in Europe. The results of this study are significant in that the dose levels administered to the rats were equal to and even less than what is approved for humans.

As a result, the researchers have urged experts to call for an “urgent re-evaluation” of the current guidelines for human consumption of aspartame. “Our study has shown that aspartame is a multipotential carcinogenic compound whose carcinogenic effects are also evident at a daily dose of 20 milligrams per kilogram (mg/kg) of body weight notably less than the current acceptable daily intake for humans.”

In the study, researchers gave aspartame to the rats by adding it to a standard diet. They studied the rats from eight weeks of age and continued until the spontaneous death of each rat.

Treatment groups were fed concentrations of aspartame at dosages that simulated human daily intakes of 5,000, 2,500, 500, 100, 20 and 4 mg/kg body weight. Groups had 100 males and 100 females at each of the three highest dosages, and 150 males and 150 females at all lower dosages, as well as controls.

The experiment ended when the last rat died at 159 weeks. As each animal died, researchers looked for microscopic changes in all organs and tissues. This approach, which allowed the aspartame to fully express any carcinogenic potential, was not the approach taken during the original studies done 30 years ago.

In both males and females that were tested, there was widespread evidence of malignant cancers, including tumors, lymphomas, and leukemia in various organ sites. The control rats, however, were cancer-free.

The team believes that the increase in lymphomas and leukemia could be related to one of the metabolites in aspartame — namely methanol. Methanol metabolizes in both rats and humans to formaldehyde. In other long-term experiments, both methanol and formaldehyde have been linked to lymphomas and leukemia. (At least one expert, however, questions the “methanol” theory simply because it would be difficult to imagine a human consuming enough aspartame to satisfy the hypothesis.)

As a result of their findings, the researchers believe their study raises questions concerning the level of aspartame-exposure that should prompt an urgent “re-examination” of the subject. The critical question is: How much aspartame can be consumed (in relation to a person’s weight) without any appreciable health risk?

The study is not without its critics, however. The Calorie Control Council (a trade group of artificial sweetener makers) claims that basing conclusions on 3-year-old laboratory rats instead of the traditional 2-year-old animals skewed the results. The Council argues that cancers in older rats, just like older people, may be nothing more than the result of a combination of numerous influences and, thus, it would be error to attribute the presence of the disease to any one cause, especially aspartame.

Dr. Soffritti, however, sees the advanced age of the rats in his study as more, rather than less, indicative of the long-term effects of aspartame. Other experts agree with this hypothesis and many critics of the sweetener have always believed that Searle’s studies, as well as others funded by the industry, have been terminated too soon to accurately reflect the true long-term effects of aspartame.

As quoted in The New York Times, Dr. Soffritti stated: “Cancer is a disease of the third part of life. 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.”

Clearly, Dr. Soffritti’s study has served to intensify the debate over the safety of aspartame and to galvanize critics of the sweetener for a new round of efforts to ban it as a food additive. Thus, even those who are not willing to accept the study as definitive proof of the potential dangers posed by aspartame concede that it raises serious issue worthy of further examination.

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