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Rat Study Shows Cancer, Aspartame Link

But Critics Charge That Research Is Flawed

'Findings Speak for Themselves' continued...

Soffritti said the fact that the rats in the study died of natural causes rather than being sacrificed at a specific point in their lives helped the researchers to better identify the cancer links.

But critics contend that this was a big problem with the study. Most cancer study guidelines recommend the sacrifice of research animals at specific ages -- in the case of the rats used in the study around 104 to 110 weeks.

That would be the equivalent of age 60 or so in humans. The last rat in the study died at 159 weeks of age.

"Rats, like people, develop a wide range of cancers in old age, and establishing whether there is a cause-and-effect relationship (at an age when cancers are common) is not possible," says Joe Poulos, a spokesman for Merisant, the company that makes the aspartame sweetener Equal.

"More than 200 toxicological and clinical studies have been conducted over the past 30 years, all of which have confirmed the safety of aspartame," he tells WebMD.

Widely Considered Safe

Poulos says that regulatory agencies in 130 countries have reviewed aspartame and found it to be safe.

Most scientific organizations that have weighed in on the question have come to the same conclusion, including the American Medical Association, the American Dietetic Association, the American Diabetes Association, and the American Cancer Society.

In its report on aspartame, the American Cancer Society concludes that "current evidence does not demonstrate any link between aspartame ingestion and increased cancer risk."

In the newly published study, Soffritti and colleagues speculated that methanol, which is a byproduct of aspartame, may explain the increase in cancers seen in the study. Methanol is metabolized in both rats and humans to form formaldehyde, which is a carcinogen.

Beth Hubrich, MS, MD, of the artificial sweetener-industry group Calorie Control Council, tells WebMD that all kinds of foods contain methanol. She calls the newly published study "seriously flawed."

"You can actually find six times more methanol in a glass of tomato juice than in a beverage sweetened with aspartame," she says. "And there is no difference in the way that methanol is metabolized by the body when it comes from aspartame or from some other source like tomato or orange juice."

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