A scientific journal has formally retracted a controversial study linking genetically modified corn to tumor growth and death risk in rats.
The study had appeared in the Sept. 19, 2012 issue of Food and Chemical Toxicology, and made headlines around the world with its stark images of rats who purportedly were more likely to develop large tumors and die early after eating Monsanto’s genetically modified maize, whether or not it was treated with a weed killer.
But now the journal’s publisher, Elsevier, says the study led by biologist Dr. Gilles-Eric Seralini of Caen University in France is being retracted due to concerns with the research methodology.
Elsevier emphasized there’s no evidence of fraud or intentional misrepresentation.
“This retraction comes after a thorough and time-consuming analysis of the published article and the data it reports, along with an investigation into the peer-review behind the article,” Elsevier said in the statement. “Ultimately, the results presented (while not incorrect) are inconclusive, and therefore do not reach the threshold of publication for Food and Chemical Toxicology.”
For the original study, about 200 albino Sprague-Dawley rats were divided into groups of 10 and fed diets with GM corn cultivated with our without the Roundup weed killer, or they were assigned to drink Roundup alone in water. Twenty rats served as controls.
Female mice on GM diets were found to be two to three times more likely to die than those in the control group, and their health seemed to be more negatively affected by the diets whether it was sprayed with Roundup or not. About 50 percent of males and 70 percent of the females eating Monsanto GM corn died prematurely, compared to 30 percent of males and 20 percent of females not eating the corn.
Large mammary tumors developed in female rats about four months into the two-year study, some that were so large they blocked organ function.
Yet, some experts at the time questioned the findings, nothing Sprague-Dawley rats are more likely to develop tumors anyway, and that 20 rats make for too small of a comparison control group.
“The most evocative part of the paper is those pictures of tumorigenesis,” said Maurice Moloney, a research biologist at Rothamsted Research in Harpenden, England, said in Sept. 2012. “If there was a control that ended up showing similar kinds of tumorigenesis then a picture of that rat should be shown as well, just so we can see if there are any qualitative differences between them.”
The journal’s editor-in-chief began to review these questions and allegations soon after the study was published, and requested to see all the raw data from the researcher, with Seralini complying.
A “more in-depth analysis” showed that “no definitive conclusions can be reached with this small sample size… in regards to overall mortality or tumor incidence.”
Given these rats are more likely to develop tumors, normal variability cannot be excluded as a cause of what the researchers found, according to the journal.
“The peer review process is not perfect, but it does work,” said Elsevier. “The retraction is only on the inconclusiveness of this one paper. The journal’s editorial policy will continue to review all manuscripts no matter how controversial they may be.”
Nature reports the news shouldn’t come as a surprise, because editor-in-chief Wallace Hayes announced earlier this month that he’d retract the paper if Seralini and his colleagues didn’t withdraw the study, which the team reportedly refused to do at a Nov. 28 press conference, standing by their research.
Seralini told Reuters the criticism of his work was “unacceptable” and threatened legal action.
Joel Spiroux, president of the France-based Committee for Research and Independent Information on Genetic Engineering (CRIIGEN), which collaborated on the study, called the retraction a “a public-health scandal” to Nature.
Monsanto could not be reached for comment at press time.