May 28, 2024

EFSA Says French GM Corn Study Not Valid; Others Disagree

The study that was released last month by a French research team headed by Professor Gilles-Eric Séralin was the first to find that genetically modified (GM) corn produced tumors in rats. It was published in the journal Food and Chemical Toxicology. But the European Food Safety Authority has released a statement saying that the study did not conform to standard study protocols and the organization is “unable to regard the authors’ conclusions as scientifically sound.”

HospitalThe criticisms focus on the methodology of the study instead of the results. All scientific studies must adhere to a certain methodology in order to produce results that are replicable, clear, and free of bias. The EFSA is planning to release a second review at the end of this month which will include additional information from the study’s authors.

This study directly refutes the Monsanto study that found the Roundup Ready Corn was safe for human consumption. That study followed the animals for 90 days. Séralin’s study found that the rats developed tumors after four months of being fed the GM corn. The criticisms of the study and Dr. Séralin’s responses as published by Sustainable Food Trust include several points.

First, the strain of rat, the Sprague Dawley rat strain, used in the study is prone to developing tumors over their two year life expectancy, which was not discussed by the authors. Dr. Séralin says they used the same rats that were used in the Monsanto study and that the SD rat cancer pattern accurately mirrors that of humans. Furthermore, that rat strain is an “excellent human-equivalent model for long-term carcinogenicity studies.” Second, the sample size of rats was too small to reach statistically significant conclusions. Dr. Séralin responds that Monsanto used the same number of rats in their study.

Third, the study only had one control group, even though there were ten treatment sets. Dr. Séralin says that the control group parameter is the same as used in industry, and that there are large differences in tumor frequencies between the control and experimental groups. In fact, the differences are so large there was no need to conduct statistical tests. Fourth, the tumor rates did not increase in line with the dose of GM foods fed to the animals. Dr. Séralin says that this is not a “regular poison effect”, but hormonal system disturbances, which display nonlinear effects.

The main conclusion of the paper is that the Monsanto study only lasted for 90 days, and the French study found tumors developed after 120 days. The study’s authors did stress that more research, in longer time frames, needs to be conducted to reach solid conclusions.


  1. One of the problems I had when I ate GM foods, was severe stomach pains. I quit eating foods and products that contain any of them, and my stomach pains cleared up. Sadly, my brother ate the foods and products that are GM adulterated, including corn. He suffered severe stomach pains, despite meds and other GI treatment. I’ll never know, if GMOs caused the stomach cancer that killed him 3 years ago.

    Obesity and diabetes are increasing at an alarming rate. My brother-in-law developed both, a few years ago. His funeral is Friday.

    Corn is fed to cattle to fatten them up for slaughter. So, what is corn doing to people. Think about it.

    I don’t eat corn. I weigh 100 pounds.

  2. Why don’t they study all the lab rats that are already in the US. All of us people, pets, farm animals and wildlife that have been force fed GMOs for many years. Perhaps, it is a case of ‘don’t look, don’t find’. Many people have already discovered that we can’t tolerate GM foods or products that contain them. We avoid the GMOs, and won’t feed them to our pets, either. Hard to do without truthful labels, but we do the best we can.

    • Rosalind Dalefield says

      A n interesting point. The health of the general popultion in the US is in fact closely monitored and regularly reported. GM plants have been a normal part of the US diet for years now, but age-adjusted incidence of cancer have been steadily DECREASING in the US population for every type of cancer except lung cancer (caused by smoking), cervical cancer (caused by human papilloma virus infection) and, in white people, malignant melanoma (caused by excessive UV exposure). With the exception of those who can’t afford health insurance, Americans are living longer than ever before, and are remaining healthier into old age than they have ever done in the past.

  3. Rosalind Dalefield says

    Dr Seralini is wrong. Sprague Dawley rats are not an excellent model for long-term carcinogenicity studies. They are very poor model because of their high spontaneous rates of tumours including the mammary adenomas observed in the study. The rat model of choice for carcinogenicity studies is the Han Wistar rat, which is longer-lived, less inclined to become obese, and has lower rates of background tumors. I have run carcinogenicity studies using both models and have seen many, many adenomas of the kind Seralini found in female Sprague Dawleys. They are most likely in the females that are most obese, i.e. the ones that are doing the best in the short term.
    The other, greater problem with the Seralini study is that they used only 10 rats/sex/group. Carcinogenicity studies should have at least 50 rats/sex/group to have adequate statistical power to detect differences in tumor incidence, because of the stochastic nature of carcinogenesis. The USFDA and other regulatory bodies would never accept a rodent carcinogenicity study with less than 50 rats/sex/group at the outset, for this reason. In fact they will not accept a study that has less than 25 rats/sex in the control group at the end of the study, and require studies to be brought down early if the control group reaches 25 rats/group. This required for results that are statistically meaningful. Seralini’s results are meaningless.

    • Linda Larsen says

      Interesting. How do you respond to the fact that Monsanto used Sprague Dawley rats and that same number of rats in their study that showed Roundup Ready Corn is “safe”?

      • Rosalind Dalefield says

        Monsanto’s study was a 90 day toxicity study. Sprague Dawleys are routinely used in toxicity studies because they mature quickly and because their high spontaneous tumor prevalence is not an issue in 90 day studies. It is standard to use 10 rats/sex/group in a toxicity study because toxicity is not a stochastic event like carcinogenesis. On the contrary, if the dose of a substance is over the toxic threshold, most or all of the rats in a group of 10 will show the effect. 10 rats/sex/group is therefore an appropriate number for a toxicity study, and provides adequate statistical strength, but it is a hopelessly inadequate number for a carcinogenesis study, and cannot possibly provide adequate statistical strength. Comparing toxicity studies with carcinogenesis studies is not just comparing apples and oranges, it is comparing apples and truffles.

        • Linda Larsen says

          Monsanto needs to do a long term carcinogenesis study. Why haven’t they? Because they had a supposedly “clean” toxicology study they didn’t need to meet the criteria for the Delaney clause that forbids the use of any substances that induces cancer in man or other animals. No one who supports GMO products has answered my question: why did Monsanto stop their study at 90 days? Why not conduct longer tests?

          • Rosalind Dalefield says

            Monsanto, like almost every other company producing products that require regulatory oversight, do the studies that regulators require. Animal studies, particularly 2-year carcinogenicity studies, are fantastically expensive and if international regulatory bodies do not require carcinogenicity studies for GM foods, then there is no reason for Monsanto to do them. A 90-day study in rats is more than adequate to detect chronic toxicity, because it is equivalent to 10 to 15 years of a human being’s lifetime. There is no indication that GM foods have any genotoxic effects and therefore there is no scientific justification for conducting carcinogenicity studies.

          • I agree with Linda. Monsanto is making billions of dollars on these products. They can certainly afford to conduct carcinogenicity tests, especially after results like the French study. And 10 to 15 years of a human being’s lifetime is NOTHING. The rat toxicity studies should be for the entire rat’s lifetime, so it is more equivalent to the human being lifespan. Monsanto is trying to get away with something. And there certainly is indication that GM foods have genotoxic effects.

    • John Wagoner says

      Thank you Rosalind for that insight. Can you comment on the other pathologies. In addition to the cancers, weren’t the experimental rats having significant pathologies involving liver and kidney damage / failure as compared to the control ?

      There seems to be enough data here to warrant more robust, independent replication of these observations for a period representing the life of the rats.

      Aside from the question of if the science is robust, weak, questionable or not, the basic issue in the U.S. is that GMO products are Secretly incorporated into our food, and we have a basic right to know the food ingredients so we can make our own decisions.

      Its outrageous that our governments have been so heavily influence by industry as to have allowed the secret inclusion of GMO into our food supply for as long as it has happened.

      • Rosalind Dalefield says

        I have a copy of the Seralini paper in front of me right now, and I have read it, and tried to make sense of it, several times. The alleged increase in liver and kidney damage cannot be verified by the data presented, and Seralini et al have refused to release their raw data, which is not the typical conduct of reputable scientists. Liver and kidney failure are both very common age-related events in Sprague Dawley rats. The very limited data presented actually show that the incidence of liver pathology does not increase with increasing dose of GM feed or of Roundup, which a toxicologist would conclude is evidence that the liver pathology is unrelated to the GM feed or the Roundup. There are no data on clinical pathology related to liver function, and the clinical pathology data presented related to kidney function are presented in such an eccentric manner that they are impossible to interpret.
        In my opinion as a double Boarded toxicologist, with a PhD in veterinary pathology and years of experience in conducting rodent toxicology and carcinogenicity studies, there is not enough evidence here to warrant any replication efforts. Roundup, being a herbicide, was subject to comprehensive testing in rodents prior to approval and none of those studies showed any of the effects claimed in this paper. It is astonishing to me, and a number of toxicologists of my acquaintance, that this paper ever made it through peer-review.
        Seralini et al have a previously established history of claiming deleterious liver and kidney effects on the basis of DECREASES in serum markers of liver or kidney pathology in treated rats relative to controls. In other words, in situations in which a clinical pathologist would say that the data showed that the liver and/or kidney function was if anything better in the treated animals than the controls, Seralini et al claimed the opposite.
        As for whether foodstuffs containing GM food should be labelled or not, I think that is a separate issue entirely.

        • John Wagoner says

          Its my understanding that Seralini is refusing to release his raw data until Monsanto does the same with the data they used to justify the safety of their product. So much for transparency in science.

          It doesn’t bother you that these GMO products are secretly incorporated into prepared food ? I for one refuse to function as free Guinea pig for the Monsanto corporation.

        • John Wagoner says

          Upon further reflection, the fact that you are willing to impugn Seralini et al reputations by stating the fact they are refusing to release their data but not stating the reason why ( they are demanding Monsanto release theirs ) reveals you are willing to build your arguments on Half Truths, and I suspect all your opinions. When corporations won’t release their raw data, then they are most likely hiding the fact that they have only published the data that supports their economic interests. I assume people who pretend half truths make credible arguments are influence by conflicts of interests.

  4. John Wagoner says

    How is it that the study by Gilles-Eric Séralini uses the same experimental protocol ( sample size, rat variety, etc. ) that Monsanto used to justify the safety of their Round Up Ready Corn, just tested the rats for their life span, instead 90 days, and these experiments are somehow not valid ? I smell corporate rats.

    Since 70 percent of the corn grown in the US is the Monsanto varieties then its safe to conclude if the product ( made from corn ) is not labeled organic then it is secretly made from GMO corn. Think about those pictures of the rats with tumors the next time you eat your corn flakes !!

    If you care to read the an article on this subject that’s not propaganda, google: Study linking GM maize to cancer must be taken seriously by regulators by John Vidal, Guardian.

    Why have no newspapers run a story on these studies. Only critical editorials have been published. Shouldn’t the possibility of the corn being unsafe be headlines news ??

    • Linda Larsen says

      That is why I put the responses by Dr. Séralin into the story. I think the critical point is that his studies were conducted longer than the Monsanto studies and showed significant problems. Notice that the critics don’t point that out. We need long term studies on GM foods.

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