Séralini Paper Retracted – GMOs do not cause cancer in Rats

Just a year ago a paper by Gilles-Eric Séralini published in the Journal of Food and Chemical Toxicology, Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize created a stir in the anti-GMO community. It was touted around the world as the definitive proof that GMOs caused cancer, just as many had decided many years ago. This month, the paper was retracted, which means that it has been removed from the archives of the journal, and we should consider that the paper had never been published.

The paper was plagued with criticism from the very beginning; from the way it was released to the methodology and the analysis. First of all, the paper was released to journalists, who were required to sign a confidentiality agreement. This allowed the author to control the message without being concerned about the detailed analysis that independent scientists can provide. This technique is considered both bad science and bad journalism.

Besides criticizing the way the paper was released, scientists were critical of the work itself. One of these who offered a detailed critique was pseudonymous writer Scicurious in Discover Magazine.

Following the release of the study, numerous scientists questioned the findings, citing “anomalies throughout the paper that normally should have been corrected or resolved through the peer-review process.” In particular, there are problems with the statistics performed on the data, the way the data were presented, and the numbers and types of animals used in the study.

With out going into too many details here, the number of controls for the different comparisons was inadequate.

In most well-performed experiments, there would be a separate group of control rats for each condition, the GMO food alone, the GMO + Roundup, and the Roundup alone. The controls used for the study, as Anthony Trewavas, a cell biologist at the University of Edinburgh, pointed out in a press release response, are “inadequate to make any deduction.”

In addition, the rats used were a type bred to develop tumours even without interventions of any sort.

Up to 57% of female Sprague Dawley rats have been shown in other studies to develop tumors, especially mammary tumors, spontaneously. Males develop tumors at fairly high incidence as well. But in their striking mortality numbers for the study, showing the type and incidence of tumor development, the authors of the study do not show any of the control groups, and so we cannot actually compare the death rates of any of the GMO and Roundup exposures to controls.

The statistical analysis was also partially over-simplified and partially unnecessarily complex.

In comparison to the 50% male death rate for the GMO maize diet…is a 30% death rate in controls any better? There are no statistical analyses of how death rates compare between the different treatment groups and controls, only percentages. The way the data were analyzed is also unusual and highly complicated. This struck many of the scientists who read the study (including me) as odd. When comparing groups of doses as these authors did, there are simple enough statistical tests that will easily differentiate among the groups.

Scicurious sums it up succinctly;

All we can really conclude is that rats who are prone to develop tumors…develop tumors, whether they are fed GMO maize, Roundup, both, or neither.

Similar criticisms came from other scientists as well. A group of French researchers raised many of the same concerns. The European Food Safety Authority recognized the flaws and refused to accept the findings. Mark Tester, from the University of Adelaide and David Spiegelhalter of the University of Cambridge were two others who were skeptical of the study. David Tribe at the website Biofortified also wrote a detailed analysis of the flaws in the paper.

These are just a few of the criticisms that were raised within the first month following publication. Since then, two things have happened. Those who are opposed to GMOs have trumpeted the study as proof of what they have known since the first GMOs were developed: these are unnatural products and are therefore harmful to people and the environment. On the other side, more and more scientists have spoken out about the flaws in the study both in public and in letters to the journal culminating in the retraction of the paper.

Séralini and his supporters have responded by claiming that Monsanto stacked the editorial team of the Journal of Food and Chemical Toxicology to suppress his findings and by threatening lawsuits to have the study reinstated.

On the other side of the GMO argument, an analysis of studies conducted over the past ten years was published in the Journal Critical Reviews in Biotechnology. The results directly contradicted Séralini’s findings by demonstrating a complete lack of danger in GMOs.

An overview of the last 10 years of genetically engineered crop safety research Alessandro Nicolia, Alberto Manzo, Fabio Veronesi, and Daniele Rosellini

The technology to produce genetically engineered (GE) plants is celebrating its 30th anniversary and one of the major achievements has been the development of GE crops. The safety of GE crops is crucial for their adoption and has been the object of intense research work often ignored in the public debate. We have reviewed the scientific literature on GE crop safety during the last 10 years, built a classified and manageable list of scientific papers, and analyzed the distribution and composition of the published literature. We selected original research papers, reviews, relevant opinions and reports addressing all the major issues that emerged in the debate on GE crops, trying to catch the scientific consensus that has matured since GE plants became widely cultivated worldwide. The scientific research conducted so far has not detected any significant hazards directly connected with the use of GE crops; however, the debate is still intense. An improvement in the efficacy of scientific communication could have a significant impact on the future of agricultural GE. Our collection of scientific records is available to researchers, communicators and teachers at all levels to help create an informed, balanced public perception on the important issue of GE use in agriculture.

The key phrase is bolded: The scientific research conducted so far has not detected any significant hazards directly connected with the use of GE crops.

Since the paper itself is not available to me, I turned to The Skeptical Raptor for further comments:

  • the scientific literature was heavily in favor of the safety, to both the environment and to humans, of GM based agriculture.
  • Environmental impact studies are predominant in the body of GM research, making up 68% of the 1,783 studies. These studies investigated environmental impact on the crop-level, farm-level and landscape-level. Nicolia and his team found “little to no evidence” that GM crops have a negative environmental impact on their surroundings.
  • Little to no evidence that GM agriculture harms native animal species.
  • Non-GM crops actually tend to reduce biodiversity to a higher degree.
  • Genes of GM crops can spread to wild plants, other crops and microorganisms. However, the authors state that this type of gene transfers occurs naturally all the time with non-GM crops. In fact, local plant genotypes get supplanted by non-GM crops genes. The study also stated that wild plant populations frequently mutate and become resistant to herbicides, so they form their own genetic modification (what we call evolution). Soil bacteria can take genes from all kinds of plants and other microorganisms, but that’s not harmful, it’s part of how evolution proceeds.
  • GMO crops are safe for humans and animals to consume. Before any GM crop can be shipped to a grocery store, they must be shown to be substantially equivalent to non-GM foods. In other words, GM crops should have no toxic biomolecules and have similar (if not more) of the nutrients found in the non-GM foods. This is known as substantial equivalence, and the Italian researchers could not find a single credible paper that demonstrated that GM foods had any detrimental effect on animals or humans that consume them.
  • DNA from GM crops cannot be incorporated into our DNA. This is one of the most ridiculous (and pseudoscientific) claims of the anti-GMO groups. We ingest a lot of DNA every day (from meats to raw plants), and it just doesn’t happen. Most of the DNA is broken down in the digestive tract. And if it were so easy to inject genes into the human genome, then we could really stop spending money trying to figure out how to transfer genes for medical purposes. But what we found out about gene transfer is that it’s so difficult that it may not ever be useful as a medical treatment. What makes anyone think that consuming transgenic DNA (which really is just DNA) will somehow do something that just can’t be done intentionally.
  • In the food and feeding category, the team found no evidence that approved GMOs introduce any unique allergens or toxins into the food supply. All GM crops are tested against a database of all known allergens before commercialization and any crop found containing new allergens is not approved or marketed.

Of course, none of this will be enough to convince the true believers. They will continue on with their campaign against genetically modified plants and animals, while ignoring the scientific consensus and the importance of these products to the future of agriculture.

This type of public scaremongering in the face of scientific research is reminiscent of the anti-vaccine furor created by Andrew Wakefield following his 1998 paper. Despite the fact that both the paper and Wakefield have been totally discredited, the paper is still widely believed, and Wakefield a hero to his supporters. This is fuelled by active campaigners and a credulous media, who are more interested in controversy than facts. The result is unnecessary illness and death as in some areas vaccine use has dropped below critical levels.

People such as Gilles-Eric Séralini, Andrew Wakefield, and Magda Havas are not maverick researchers who have uncovered harms that the rest of the scientific community have missed or deliberately suppressed. They are experts in self-promotion and spread FUD (fear, uncertainty, and doubt) in an effort to promote their own agendas.

Science is a messy business and scientists are human beings. Some studies may contradict the prevailing understanding, but the majority of them will be discarded along the way. As time goes on, some theories will be refined and some totally discarded. However, jumping in with a knee jerk reaction every time a study reinforces or contradicts your own biases is no way to promote science or develop public policy.


5 Responses to “Séralini Paper Retracted – GMOs do not cause cancer in Rats”

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  2. Jeff says:

    I find the criticism of having several control groups puzzling. Having a control group for each treatment group essentially means running different experiments and inflating the likelihood of a Type 1 error – and I’ve never seen an experiment run like this. But yea, otherwise it sounds like this study was horrible in many many ways. Thanks for the info.

  3. Becky says:

    It doesn’t take a rocket scientist to figure out food bioengineered to withstand weed killer cannot be good for humans. If bt toxin in corn causes necrosis in the intestines of the bees and insects then I am sure there is microscopic hemorrhaging in human intestines!! As a nurse who has seen a massive increase in GI DISORDERS AND AUTOIMMUNE DISEASES OVER THE LAST TEN YEARS I DONT NEED A THINK TWICE ABOUT NOT EATING GMO’S!

    • chris says:

      Welcome to a skeptic blog Becky, where anecdotal evidence, speculation, and irrational fear all do not equal causation. Over the last 30 years a whole lot of scientists (although not aeronautic ones) have figured out to a high degree of certainty that GE food IS safe. The weed killer you speak of (I’m assuming you’re talking glyphosate aka Round-up) actually has very low toxicity in humans and has a far lower environmental impact than some organic farming herb/fungicides like copper and sulphur which are less effective than synthetics and must be applied more often and at higher rates …

      You do realize Bt endotoxins are used as a pesticide for conventional and organic farming too (since the 1920s), and that studies have shown no significant adverse affects on bees (http://hal.archives-ouvertes.fr/docs/00/89/22/71/PDF/hal-00892271.pdf). The endotoxins are extremely specific and to steal from Myles Power:

      “Even though the toxin is so specific, some people seem to be under the impression that what kills one organism will kill another, but we all know this not to be true, otherwise we would not take penicillin to kill a bacterial infection, and we would have no problem feeding chocolate to our dogs. The Bt delta endotoxins are so non-toxic to mammals that when mice where fed 3,289mg/kg of one of them (CryIAb delta endotoxin) in a single dose, no adverse effects were recorded. (http://pmep.cce.cornell.edu/profiles/biopest-biocont/bioinsect/bac_thur/btcry1a_endotoxin/btendo_exm_corn_0895.html). To put that in context, that would be the equivalent of the average British man (who weights 84kg) eating 276.3g of the purified toxin and having no adverse effects.”

      I suggest you read Nicolia’s meta-study refered to in the article which can be found here:

      GE crops are the most tested foods that have ever been produced; Nicolia reports that 770 papers on human and animal interaction in the past 10 years! A few notes from the study:

      - Humans consume between .1 and 1g of DNA per day. Transgenic DNA is enormously diluted by the total amount of ingested DNA (from 0.00006% to 0.00009%) and is digested like any other DNA (Parrot et al., 2010).

      - the antibiotic resistance genes found into GE crops today do not present any significant risk to human or animal health (Ramessar et al., 2007), and they are already naturally present into the environment and/or the human/animal GI (EFSA, 2011; Wilcks & Jacobsen, 2010).

      - No evidence has been obtained to date that DNA absorbed through the GI tract can be integrated into the cells of the host organism and lead to a germ line transfer.

      On safety of transgenic products (stuff like the insecticidal proteins produced by Bt varieties):

      - during the digestion process the proteins generally undergo degradation that leads to the loss of activity (Delaney et al., 2008)

      - the consumption of transgenic proteins contained in the authorized GE crop does not result in any detectable systemic uptake (Kier & Petrick, 2008) and transgenic proteins are usually rapidly degraded and not detectable in animal derived products (e.g. milk, meat, eggs) (Ramessar et al., 2007)


  • John Underhay

    John Underhay, also known as Peicurmudgeon, is just your average atheist, left leaning, SCUBA diving, snorkeling, biker. He lives on PEI and spends some of his time attempting to point out the flaws and or dangers in promoting ideas that run contrary to the laws of physics, chemistry, or biology. He has a BSc (Biology) and an MSc (Pharmacology) from the University of Prince Edward Island, and is currently retired. You can read more of his posts at http://peicurmudgeon.wordpress.com/