Earlier we explored the debate over Prop. 37, the November ballot initiative that would require labeling for some genetically modified foods. Backers of Prop. 37 have pointed to a new weapon in their arsenal: a study published last month that claims to prove that genetically modified corn causes tumors in rats.
At first, the paper published in the journal Food & Chemical Toxicology shocked plant scientists and genetic researchers. A team in France fed groups of male and female rats genetically modified corn produced by Monsanto. The company added a toxic protein to the corn to make it resistant to its herbicide, Roundup.
French molecular biologist Gilles-Eric Seralini says rats of both genders developed liver and kidney problems. Many died. Seralini, who led the study, speaks through an interpreter in part of the video. Here he describes tumors on the rats the size of tennis balls. Again, it's translated. But at least one word in French catches the ear: "enorme." Nearly eighty percent of the female rats in the study that ate Roundup-ready corn developed tumors.
Seralini is an unapologetic activist, the founder of his own research institution on GMOs.
In this video, found on the website of his research group, CRIIGEN, Seralini says the way European governments permit GMOs is scandalous, because approval is based on 90-day tests.
That's why Seralini says he designed his study to last two years.
“We tried to evaluate a maximum of biological and biochemical parameters,” the voice over translation says, in English, “with repeated blood tests, weighing of the specimens, and urine tests.”
But Alan McHughen, a geneticist at UC Riverside, is not impressed. “Most of the scientific communities are saying that this study is meaningless,” he says. “But the damage is done because it already got the big media push.”
McHughen objects to the fact that Seralini’s team hasn’t released all of its data. And he says it’s really inappropriate that Seralini asked reporters seeing the paper in advance to sign confidentiality agreements. “Unprecedented,” he says.
NYU food policy professor Marion Nestle, a supporter of the GMO labeling movement, takes issue with how the study presented its results. She says Seralini’s team didn’t do a statistical analysis common to this type of study, an analysis needed to back up the conclusion that the tumors were caused by GMOs.
"Until they do, the question remains open about whether the results that they got are just a statistical fluke or something that occurred by chance,” Nestle says. “I don’t think that’s excluded by the data, and I wish they had done that.”
Alan McHughen of UC Riverside says Seralini’s study has another big methodological weakness: its subjects are a breed of rats called Sprague-Dawley.
“It’s suspicious that they chose this particular strain of rats and without disclosing in the manuscript that it was a strain that was known to be prone to produce tumors spontaneously,” he says. “That’s a big issue.”
McHughen points out that twenty to 30 percent of the control group rats, the ones that did not eat GMO corn, developed tumors, too.
Seralini’s supporters counter that Monsanto studies that found genetically modified corn to be safe used the same rats. Michael Antoniou is a geneticist at Kings College in London and a member of Seralini’s research organization.
“This Seralini project was a direct follow up using exactly the same experimental design as what industry did before,” Antoniou said on a recent visit to Los Angeles. “So either both are correct, or both are wrong.”
The most radical claim Seralini has made in releasing his study is that the mere act of changing the genetic makeup of corn makes it harmful to eat.
Again, from the first video embedded above, a translation: “The biggest surprise came when we realized that GMOs without any Roundup residue were responsible for deaths in the increase in the death rates of females and some males.”
That’s the kind of allegation that angers plant biologists like Ottoline Leyser, who works at the University of Cambridge.
“There is nowhere in the paper where it says that the reason for the problem is that the thing was genetically modified generically,” she says. “It says it’s to do with the protein introduced by the GM, not to do with the process by which it was introduced.”
Opponents of Prop. 37 say that, with all of its flaws, the Seralini study cannot be used as an argument in favor of Prop 37. The scientists who find fault with the study say there is little high quality research on the long-term benefits and possible risks of GMOs. Most of them want to see more.