Researchers at the University of Caen in France claim that a diet of Monsanto’s genetically modified (GM) maize—which has been approved for consumption in the United States since 2000—caused rats to suffer organ damage, develop debilitating tumors, and die early. But the 2-year study, which was published yesterday (September 19) in the journal Food and Chemical Toxicology, has drawn swift criticism from scientists who point out missing data and questionable methods.
In the study, researchers divided rats into 4 groups: one fed GM maize—resistant to Monsanto’s week-killer, Roundup—that had traces of Roundup; a second fed GM maize without Roundup; a third fed conventional maize and Roundup-laced water; and a control group given conventional maize and pure water.
Within 2 years—a rat’s normal lifespan—the study reports that of the rats fed GM maize, 50 percent of males and 70 percent of females died early, compared to 20 percent of males and 30 percent of females in the control group. Further, researchers noted liver and kidney damage and large mammary tumors in the rats fed GM maize.
But other scientists found flaws in the study. “This strain of rat is very prone to mammary tumors particularly when food intake is not restricted," Tom Sanders, head of nutritional science research at King's College London, told Rueters. He noted that the study did not disclose the rats’ food intake or growth rate.
He added that he was also suspicious of the analysis. “The statistical methods are unconventional,” he said. “It would appear the authors have gone on a statistical fishing trip.”
Mark Tester, a plant geneticist at the University of Adelaide, further questioned how scientists could have missed such significant health threats in the past. “If the effects are as big as purported, and if the work really is relevant to humans, why aren't the North Americans dropping like flies?” Tester wrote to Reuters in an email.
But Michael Antoniou, a molecular biologist at King's College involved with the study, stands by the findings. The data is “strong enough to withdraw the marketing approval for this variety of GM maize,” pending further testing, he told Reuters.