Scientist deconstructs Séralini’s PLOS GMO study: ‘Failed attempt at redemption’

Gilles-Éric Séralini, a molecular biologist at the University of Caen in France, is hoping for redemption with a new paper about the effect of pesticides and genetically modified (GMO) feed on rats and mice. He hasn’t earned that redemption.

A few years ago, Séralini suffered the ultimate humiliation for a scientist. The Journal Food and Chemical Toxicology retracted his high-profile study. The editors reviewed the raw data and found the results were “inconclusive” and did not back the conclusions that were loudly trumpeted in media headlines. The authors themselves eventually conceded that the study had serious flaws, noting in a press release that “the data are inconclusive, due to the rat strain and the number of animals used.”

Other long-term studies, which were publicly funded, had uncovered no health issues with GMO corn or the herbicide glyphosate. The Japanese Department of Environmental Health and Toxicology released a 52-week feeding study of GM soybeans in 2007, finding “no apparent adverse effect in rats.” In 2012, a team of scientists at the University of Nottingham School of Biosciences released a review of 12 long-term studies (up to two years) and 12 multi-generational studies (up to 5 generations) of GM foods in the same journal that published the Séralini paper, concluding there is no evidence of health hazards.” Consequently, there was growing pressure on the journal to retract the original study since publication in 2012, along with other criticisms and an exchange of letters in the journal.

Now, Séralini has a new study, released July 2 after being delayed more than two weeks, in which the authors measured the levels of various pesticides, industrial chemicals and genetically engineered crops in 13 brands of laboratory rodent feed. (NOTE: An earlier version of the embargoed journal article had been distributed to journalists and numerous news outlets, and Séralini’s own vanity site has broken the embargo.) There seems to be nothing wrong with the data itself. The results themselves of are not surprising given the currently planted genetically engineered crops and current pesticides usage.

  • GLP has assessments from the latest Séralini study by scientists from around the world here.
  • GLP has a profile of Séralini and his research here.

The authors take these unsurprising results and call into question the validity of everyone else’s studies. The conclusion, as explained in a university press release, is unfounded: “It therefore appears that the cause of diseases and disorders found in laboratory rats has been too quickly attributed to the genetic characteristics of the species used.” In other words, the rats are dying from GMOs and pesticides like glyphosate in feeds.

As a neuroscientist who works regularly with lab animals, I find these claims baffling.

These results do not mean much, given the absence of any data suggesting a correlation between diet and phenotype, a trait, in laboratory rodents. They have presented zero evidence from their own work or published work that feed contamination is an issue for laboratory animal health. They present no data on animal health and no data about which feeds, fed to which strains produce which pathological phenotypes. They also completely ignore the fact that different strains of rodents have different phenotypes and rates of spontaneous pathology. The authors have made a huge logical leap in concluding that this data calls into question all historical data used as external controls.

Fortunately, the very historical data that the authors are attempting to discredit are unlikely to support their conclusion.

I would also argue that if such changes in the phenotype of well-characterized strains of lab rodents were occurring, the scientists who work with these animals would notice. When your control animals don’t behave as expected (in their behavioral response, pathology, life span, reproductive success, anything really), this is a big red flag. If there was an issue with feed causing significant pathology in laboratory rodents, this is something that would be seen in labs around the world.

If we wanted to mine the existing data to address some of these concerns, here are a few question we can ask to explore if these chemicals or genetically engineered crops in laboratory feed affect the phenotype of laboratory rodents.

When genetically engineered crops were introduced in the 1990s, did control mice start having different phenotypes? We can pull the rates of spontaneous pathological effects from papers published before and after the introduction of the relevant genetically engineered crops and compare them. If there is no difference in control animals before and after the introduction of genetically engineered crops, then the GMO composition of laboratory feed has had no effect on the health of lab animals.

A study published last year by University of California-Davis animal geneticist Alison Van Eenennaam did just that with livestock. Her team examined almost 30-years of livestock studies, more than 100 billion animals, comparing their health before and after GMO feed became the norm. She found no difference in the animals.

1) Some commonly used lab strains have been used for 70+ years. The pesticide residues found in laboratory feed reflect the pesticides in current use, just as pesticide residues on food reflect current pesticide use. So an obvious question is: have the phenotypes of these mice changed as our pesticide use has changed?

Related article:  Viewpoint: Roundup is a 'timid cousin' of dangerous pesticides, and a blessing to agriculture

When organochlorines were banned in the 1970s and replaced by organophosphates, was there a concurrent change in the phenotype of lab animals? As use of organophosphates has declined more recently, have we seen a change in the animals? As glyphosate has replaced more toxic herbicides have we seen a change in lab animal health? Again, we can assess this by comparing control animals in different decades. If the phenotype of control animals has been consistent, these changes in pesticides residues found in laboratory feed have had no effect on their health outcomes.

2) In the paper, the two feeds used in Italy had the highest amount of contaminants, according to the authors. This leads to the question: do lab animals in Italian labs have a different set of phenotypes as a result of eating this specific brand of feed? A more general way to put that question is to ask if the same lab strains fed feed with different contaminant profiles have different phenotypes?

We can easily mine existing data to address these questions. Let’s look at Sprague-Dawley rats as an example to answer the first two questions. These rats were originally bred in 1925 so they have been used experimentally for enough time to answer questions 1 and 2 above. If we look at historical and current data on these animals, we can see if there have been any changes in their background phenotype. This has already been addressed in a rebuttal letter to a previous paper from Séralini’s group. The rate does not appear to have changed.

This specific breed of rats is well known to be prone to develop cancer with age and especially when there is no dietary restriction. For example, Prejean et al. (1973) noted a spontaneous tumour incidence of 45% in 360 Sprague–Dawley rats (179 males and 181 females) in an 18-month series of carcinogenesis experiments. The percentage of female rats with tumours was almost double that of males. Durbin et al. (1966) reported a mean incidence of 71%, the peak incidence in normally aging rats were age-related with abrupt increases in the rate of development of mammary tumour, one occurring at about the 500th and the other at about the 660th day of life, with the median age at 671 ± 41 days. Harlan, the company that marketed the animals, describes the high incidence of 76% of mammary gland tumours (predominantly fibroademonas) in females on Life-span and Spontaneous Disease of Sprague-Dawley. Keenan et al. (1995) describes spontaneous tumours in up to 87% of females and up to 71% of males fed ad lib. Dietary restriction significantly reduced the incidence of tumours.

3) To address the third question, we can compare data on control animals from studies done in different countries. Of course, the proper way to address these issues is to do a thorough meta-analysis of all control animals in studies, separated by strain. However, quick reviews of the literature for the incidence of spontaneous pathology doesn’t seem to justify such an effort. Basically, if changes in phenotype of commonly used strains of laboratory rodents were occurring, we would see it in the existing data. If adverse events were occurring in control animals, a properly conducted study would report these adverse effects and we would see these changes in behavior of control animals in the literature. There are also ethical and legal obligations for reporting such adverse events to the veterinary staff and institutional ethics boards for animal research. Furthermore, the question of why the control mice are behaving differently than all other control mice would be very interesting research question that scientists would follow up on.

The authors of this study are searching for an answer to a non-existent problem. All Séralini had to do is a literature search to determine if this is a problem. They are trying to blame external factors (chemical contamination and GMOs) for a problem of genetics. We can, in fact, address many of the issues that authors say cannot be addressed by mining the very data that Seralini and colleagues want to throw away out of hand. But they didn’t address them and thus cannot make any conclusion except that genetically engineered crops and low levels of these chemicals exist in laboratory feed.

The authors also conclude that because of the high background pathology (reminder: not demonstrated here), the recommendation to study larger groups of animals is invalid. This is not how statistics works. If your variation is higher, you need a larger group to discern a pattern. If there is, in fact, high background variation, the only thing this underscores is the important of choosing an appropriate mouse strain for your study.

Overall, this paper is a thinly veiled attempt to address the consensus scientific criticism of Séralini’s previous work. This new paper doesn’t do anything to help his case that these criticisms were not valid.

Alison Bernstein is a scientist studying Parkinson’s disease living in Atlanta with her husband, 2 kids and 2 cats. Follow her on her Mommy PhD Facebook page and on Twitter @mommyphd2.

67 thoughts on “Scientist deconstructs Séralini’s PLOS GMO study: ‘Failed attempt at redemption’”

  1. Yeah, if you think all of biomedical science “control” animals are now invalid, that’s ridiculous. I used to work at one of the world’s top research animal colonies. They carefully examine all the animals. There are staff veterinarians. Technicians are trained to look for anomalies. If they were all getting giant lumpy tumors, we’d know. These people study rodents all day long–I swear, they’d know.

    But the Italian result now makes me wonder. If that’s highly contaminated, maybe that’s what happened to those Malatesta animals. It was strange that nobody else saw what they seemed to find. Hmm.

    • I wonder how much oversight of animal welfare occurred during Seralini’s experiment. I can’t imagine a vet or animal tech worth their salt that wouldn’t be fighting for those rats to be euthanized long before those tumors grew that large. Seralini is preaching straight to the Moms Across America crowd now. Anyone with any science background realizes that he is just pointing out that lab animals have eaten millions of meals containing GM corn and soy and nobody noticed any adverse effects.

      • My thoughts exactly, Verna. This is incredibly cruel to the rats. How big do the tumors have to be before the rats are humanely euthanized? Naaaaah, he just wants to hold up a rat with a tumor the size of the rat’s body, for press and “shock and awe.” I’ve been kinda horrified at that, also.

        I would presume that any genuine cancer study wouldn’t let it get to this degree of harm to the rat, just to make a dramatic point; any bio-scientists or cancer researchers here have any comments about this? Would love to know if Seralini is way out of line in his treatment of these animals.

          • Really? That’s interesting to know. How big do you think the tumors are on those rats? Looks like several centimeters to me … is there a case for animal cruelty here? “Look how big I can grow these tumors, just in case you missed them somehow.”

            Thanks for that information. It saddens me and disgusts me to think that there’s a 2mm limit, which this jerk has exceeded by many times, just to make some kind of a “point” which has been disclaimed anyway. At the expense of these animals. So sad.

          • At contract toxicology labs I have worked at, it was not permitted to keep rats alive if the tumors interfered with normal eating or excreting, prevented/impeded normal movement, developed areas of necrosis, or were getting abraded by caging or bedding. The tumors Seralini shows off are obviously so big that they would impede normal movement, and some of them appear to be abraded too. A reputable lab would have terminated those rats long before their tumors got that big.

          • Rosalind, thank you for that explanation. In that case, Seralini is responsible for not only bad science, but animal abuse.
            He should be slammed by lab research professionals such as yourself, for this abominal treatment of the rats. All done to make a point.

          • I agree, it is definitely inhumane to keep the rats alive this long. Many critics of the original paper commented negatively about the size of the tumors. I wonder what sorry excuse for an Ethics Committee or Institutional Animal Care and Use Committee oversees his CRIIGEN Institute.
            Looking at the pictures again, that rat in the right hand picture would not be able to eat normally either. Neither of them would be able to groom themselves properly, or double themselves over to practice coprophagy, which is essential in rats for normal mineral metabolism (primarily iron metabolism if I remember correctly). Altogether, it is disgraceful treatment and proves nothing because a big tumor doesn’t prove anything that a small tumor doesn’t.

  2. No one seems to be asking why the authors are so concerned about the control rats in toxicity studies if their primary claim is that the commodity crops in commerce are causing all sorts of chronic effects? Could the focus on control rats by these authors actually be a distraction from their extraordinary contention that the residues in commodity crops are unsafe even though these levels are set at least 100-fold lower than any adverse effects seen in any animal study? Did the authors not know that the levels of potential contaminants like pesticides and heavy metals are routinely measured during toxicology tests run to satisfy regulatory requirements? Are the authors aware of the GLP regulations under which such regulatory tests are run?

    • No, they dont care at all, mix of incompetence and interest, Séralini is funded by Cere, a foundation of multinational retailer (Carrefour and Auchand) who make easy money with no GMO and organic food.

        • Looking at the activities of Greenpeace, Govt of India banned the activities of Green Peace and froze its accounts, a couple of months back. It was found by the the govt. and its all advisors that the organisation is the biggest bottleneck in its devolpment plans which need to revolve around the sustainable development relevant to roughly 1.5 billion people who need food,feed,clothing and energy and not follow the pseudoscientific hypotheses put forwarded by these people.As Prof of Biotechnolgy we witnessed the successes of GM technology in the last five decades as well as the success of medical biotechnol for the the last 65 years but a the handful of people with ulterior motives and supported by a coitre are really working against the humanity so as to meet their insatiable monetary greed. Hope other nations also follow the action of Govt of India and clears the debris created by the Green Peace, on the path of their progress.

    • I think he does, he’s just willing to trade professional credibility for ideology.

      And I think he knew about spontaneous tumor formation in Sprague-Dawley rats when he did his lousy study that got retracted a couple of years ago.

          • Like Mem_somerville had said, the first order of business for your control variables is that they are under control. He tested or had certified that his gmo-free/gly-free feed was such AND, that the other stuff had gly and or GMO feed in it.

          • I understand what you’re saying. But you have a technical background and that means that everything should make sense. And it doesn’t.

            Seralini doesn’t care if it makes sense or not. That’s not the point. He wants true believers, because true believers bring in the cash and recognition.

            I say let his bullshit play out. He can be the Heaven’s Gate or Jim Jones of anti-biotech.

          • I wasn’t disagreeing, just adding. He knows there’s no clothes and, as a degreed scientist, he went through experiment design training and stats. I wish we could all just sit back and laugh at the BS but his crap is doing real damage.

          • Let them drink their non-GMO cyanide just like the Jim Jones followers did. Good riddance to them.

      • Of course he knew. He’s a veteran scientist. A lot of people are bending over backwards to call him simply incompetent. He’s not and this new paper is proof of his intentions.

  3. Alison, this is truly an excellent explanation of how we should look at these things and why Seralini’s latest paper is one again junk.

    On reading the paper my first impressions with respect to the results was meh. They were pretty much what I would expect, small amounts of pesticides and other compounds below concentrations likely to be harmful. On reading Seralini et al.’s explanations, I was struck by how little they were supported by the results provided.

  4. Doesn’t it sound rather odd to you when then say. “This specific breed of rats is well known to be prone to develop cancer
    with age and especially when there is no dietary restriction.”. It’s as if cancer in some rats is a “normal” condition with no environmental causes. Like cancer is genetically caused in this breed, but somehow this breed survived all those reproductive generations. This whole article appears “sketchy” to me and to be motivated by big AG money.

  5. I can’t see the attempt at redemption. This is just another attempt
    to discredit the regulatory processes and, untimately, our production
    chains. It’s not science, but politics.

    Some comments here suggest that their authors had access to the
    paper. Any link available?

    • I don’t know what the original source is of this one, and it’s the pre-official PLOS one. So depending on what’s holding up the actual launch, the details may change. Follow link there to reply

      There are at least 3 versions I’m hearing of what’s holding up the paper.

      1. Big conspiracy including the State Department:

      2. Author says some revisions:

      3. Seralini says…I don’t know what he claims, I think it’s more conspiracy on this conflict of interest thing.

      • Thanks for the link, Mem. He tests for GMO’s along with pesticides and heavy metals. The rest of the paper then points out how this heavy metal or that pesticide might cloud whatever issue you might be looking at. For the GMO’s, in of themselves, he offers no such suppositions. Indeed for there is no known effect from the consumption of GMO’s simply because they are GMO’s. Hence, no NOAEL’s, no ADL’s, no MRL’s can be found or calculated for GMO’s.

        However he tries to make a link that glyphosate residues increase with the amount of RR GMO’s in the particular rat chow. And, such a link might be there though we are talking ppb’s, far, far below any NOAEL’s for glyphosate consumption, that i know of. I notice he makes no attempt to calculate any other correlations to the other pesticides and heavy metals with respect to the level of GMO’s in the rat chows.


        It seems this paper is an attempt to associate, emotionally, GMO’s with toxins by testing for them with the rest as if they were a class of toxins, as a foregone conclusion that they are, which, of course, they are not.

        One must consider, though, for his earlier rat paper, did he not test for the level of GMO’s in both his non-gmo control feed and his gmo test feed?

        Note, I am not a scientist (I’m an engineer)

          • I kind of remember a few people bringing that up, perhaps at May have been you. :)

            So Seralini’s just catching up to this. It still leaves the question as to whether he tested his own rat chow back in 2012 for levels of gly. and gmo’s. And, if he did not, is he backtracking on his own conclusions after all?

          • Remember when dear Gilles Eric got his study retracted and he threatened to sue? Which never happened. Because it was easier to blame Dr. Goodman of some kind of impropriety than to man up.

            He still has butthurt. What better way to play the butthurt card when you’ve got zero professional cred left than to blame the rat chow? Seralini’s Waterloo, if you will.

            Did you notice how he listed himself last on the author list of his latest gem? Nothing like putting the plebes in front of the cannons. Seems like he’s resorting to using human shields, Possible exit strategy? I dunno.

          • « Seralini’s Waterloo »?


            His paper was due to be published, and his media blitz to take place, on 18 June… the 200th anniversary of Waterloo.

  6. A more important question is how PlosOne proceeded to accept to
    publish the paper, and then to refuse it.

    Conspiracy theory: this was a coup to increase media attention and
    give credence to the Seralini theories. If the paper wasn’t
    published, of course under pressure from industry, it’s because he
    has unveiled an inconvenient truth.

    • Seralini had threatened to sue if the word « fraud » was pronounced.

      And we may also assume that the editor did not want to have his good name associated with… the smell of a rat.

  7. How can this Seralini character still be in the academic business? Are all of his papers so shoddy? I suspect he doesn’t really care about quality. All he has to do is crank out a bad research paper every now and then, have it rejected by the respectable journals and then claim that there is a corporate conspiracy to silence him. Then he stars in some anti-GMO documentary film that will never see the darkness of a real movie theater, but instead will hit all the usual anti-GMO venues where all the true believers will shell out their money to have their bias reconfirmed. I really think his university should investigate him.

  8. “This epistemic violence is now being combined with the violence of corporate interests to viciously attack all scientific traditions, including those that have evolved from within Western Science and transcended the mechanistic world view.Industrial-scale farming, in this way, is actually becoming anti-science.” I thought wow! Spot on. But, then I though this piece is too well thought out, it will sail right over their heads because basically their (Monsanto, DOW, BASF, BayerCropScience, Syngenta etc) science and spin are anti-intellectual … as a result we see lab techs like Robert Wager posting here and claiming to be faculty on this biotech website … know this will be hard for most of you at genetic literacy project to understand but someone can help you with the tougher words …

  9. There has been one observed change in phenotype of historical controls that is worth mentioning. I don’t attribute this to GMO feed or pesticides however (for example, some populations of wild animals also showed the trend in this study).

    Among mice in control groups in the National Toxicology Programme (NTP), there was a 11.8 per cent increase in body weight per decade from 1982 to 2003 in females coupled with a nearly twofold increase in the odds of obesity. In males there was a 10.5 per cent increase per decade. Among female rats in the NTP, there was a 0.2 per cent increase in body weight per decade, coupled with a 45 per cent increase in the odds of obesity, while among males there was a 6 per cent increase in body weight per decade coupled with a 1.25-fold increase in the odds of obesity.

  10. A study published last year by University of California-Davis animal geneticist Alison Van Eenennaam did just that with livestock. Her team examined almost 30-years of livestock studies, more than 100 billion animals, comparing their health before and after GMO feed became the norm. She found no difference in the animals.

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