Rat Study Shows Cancer, Aspartame Link
But Critics Charge That Research Is Flawed
WebMD News Archive
Nov. 18, 2005 - A study in rats links the popular artificial sweetener
aspartame to a wide range of cancers, but industry officials charge that the
research is badly flawed.
Aspartame is found in the low-calorie sweetener Equal and in many other
sugar-free products under the brand name NutraSweet. It is the second
best-selling nonsugar sweetener in the world.
Researchers in Italy concluded that rats exposed to varying doses of
aspartame throughout their lives developed leukemias, lymphomas, and several
other cancers in a dose-dependent manner.
They report that the product is a potential cancer-causing agent to humans
even at levels that are less than half of what is considered safe by the U.S.
The study appears in the Nov. 17 issue of the journal Environmental
Health Perspectives, which is published by the National Institute of
Environmental Health Sciences (NIEHS) of the U.S. Department of Health and
But critics charged that the investigators did not follow the guidelines for
scientific study outlined by the NIEHS' own research group, the National
Toxicology Program. They further noted that the NTP's own animal studies
involving similar levels of aspartame exposure showed no link between the
sweetener and an increase in cancers.
And an NIEHS spokesperson said Friday that the agency had "no role in
the design, performance, or interpretation" of the newly published
'Findings Speak for Themselves'
The study was conducted by researchers from the European Ramazzini
Foundation, an independent group located in Bologna, Italy.
One hundred male rats and 100 female rats were followed from 8 weeks of age
until their deaths from natural causes. The rats were fed aspartame at doses
approximating a wide range of human consumption levels, from very low levels to
Each rat was autopsied following its spontaneous death, and exposed animals
were found to have a higher rate of leukemias, lymphomas, kidney and pelvic
cancers and a brain cancer.
Researcher Morando Soffritti, MD, and colleagues called for an "urgent
re-evaluation" of the current guidelines for the use of aspartame.
"The findings speak for themselves," he tells WebMD. "They show
the potential carcinogenicity of aspartame in animals."
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.