Should we be concerned about the ‘Séralini studies’ that purport to show GMOs and glyphosate can cause severe harm?
At a Glance
The best known and most controversial GMO-related studies are those by French scientist Gilles-Eric Séralini, professor of molecular biology at the University of Caen. Since 2007, he has published numerous studies and non-peer reviewed reports focusing on GMOs and the herbicide glyphosate. The most contentiously received was a 2012 study of GMO corn and glyphosate published in a prominent journal and accompanied by pictures of rats with large tumors.
The article, accompanied by an anti-GMO publicity campaign, stirred intense reactions. Scientists and regulatory agencies around the world criticized its methodology, and the journal was criticized for publishing it. It was controversially retracted the following year, but was later republished in a non-peer reviewed ‘predatory’ journal.
With few exceptions, the scientific community has dismissed the body of Séralini’s work and has called for a more rigorous peer-review system in scientific journals. His anti-GMO research also has been criticized because it has been funded, in part, by the alternative health and organic industries.
Séralini supporters allege a conspiracy between regulators and the agro-chemical industry, arguring the journal retraction resulted from a pro-GMO campaign. They say this case demonstrates how the industry interferes in the scientific process. Some anti-GMO scientists have voiced support for Séralini’s work. He has become a featured spokesperson for advocacy groups opposed to crop biotechnology.
Science and Politics
In 2007, Séralini published a peer-reviewed Greenpeace-funded study that concluded there were health risks with GMO foods. The independent European Food Safety Authority and the French Commission du Génie Biomoléculaire (AFBV) found the study flawed and disputed its conclusions.
In 2009, the Séralini lab published a study concluding that the three corn crops resistant to the herbicide glyphosate caused liver, kidney and heart damage in rats. The French Haut Conseil des biotechnologies (High Council of Biotechnologies Scientific Committee or HCB) reviewed the study and concluded that it “presents no admissible scientific element likely to ascribe any haematological, hepatic or renal toxicity to the three re-analysed GMOs.”
A 2011 article by the Séralini lab reviewed 19 published animal-feeding studies, as well as data from animal-feeding studies submitted by industry for regulatory approval, concluding that GMO foods caused liver and kidney effects.
The release in September 2012 of yet another study by Séralini and his team sent shockwaves throughout because it was published in a major journal, Food and Chemical Toxicology, and was accompanied by dramatic photos of tumor-afflicted rats. Seralini released a book and film promoting his findings on the day the article appeared, and he and his supporters launched a massive worldwide public relations effort the same day.
The 24-month study, billed by anti-GMO advocacy groups as the first of its kind, centered around the feeding of GMO corn to rats. Researchers reported the development of cancerous tumors, particularly among the female rats. Among the conclusions:
The results of the study presented here clearly demonstrate that lower levels of complete agricultural glyphosate herbicide formulations, at concentrations well below officially set safety limits, induce severe hormone-dependent mammary, hepatic and kidney disturbances.
Anti-GMO forces were quick to seize on the study as evidence of the dangers presented by the genetic modification of crops. The results were released as California was in the midst of a GMO labeling ballot initiative that eventually failed. One of the campaign leaders, Gary Ruskin, now of US Right to Know, but then a leader of the California initiative, said:
This new study is destined to raise more questions than it answers. But at this point, a few things are clear. It is outrageous and shocking that this is the first long-term feeding study, even though this genetically engineered corn has been on the market for nearly 20 years.
In fact, by 2012 there were dozens of long-term studies of GMO crops (see here and here) and glyphosate and many more since, with none showing that either GMOs or glyphosate pose serious health risks.
The Séralini study touched off an international furor, widely known as the Séralini Affair. Kenya, an African pioneer in crop biotechnology, issued an indefinite ban on all GM crops, citing the study, and other African governments slowed research or put it on hold.
Séralini’s research was immediately criticized by prominent scientists (as reported here and here), who took issue with its methodology and lack of supporting data. Among the complaints was the choice of rats, a type known for its propensity to develop mammary tumors.
Regulatory agencies around the world reviewed and rejected the study’s methodology and conclusions. A joint report by three Canadian regulatory agencies identified “significant shortcomings in the study design, implementation and reporting.” Six French national academies (of Agriculture, Medicine, Pharmacy, Science, Technology and Veterinarians) issued a joint statement – a rare event in French science– condemning the study and the journal that published it. Similar conclusions were reached by the French HCB and the French National Agency for Food Safety, the Vlaams Instituut voor Biotechnologie, the Technical University of Denmark, Food Standards Australia New Zealand, the Brazilian National Technical Commission on Biosafety and the European Food Safety Authority.
The EFSA concluded:
The study as reported by Séralini et al. was found to be inadequately designed, analysed and reported…The study as described by Séralini et al. does not allow giving weight to their results and conclusions as published. Conclusions cannot be drawn on the difference in tumour incidence between treatment groups on the basis of the design, the analysis and the results as reported. Taking into consideration Member States’ assessments and the authors’ answer to critics, EFSA finds that the study as reported by Séralini et al. is of insufficient scientific quality for safety assessments
It was also noted that the French scientist’s results were far off from the reality of a world where GMO corn had by then been widely consumed by humans since 1996. In 2014, University of California-Davis Department of Animal Science geneticist Alison Van Eenennaam reviewed 29 years of livestock productivity and health data from both before and after the introduction of genetically engineered animal feed—an estimated 100 billion animals. She found no evidence that health issues escalated after 1996.
No study has revealed any differences in the nutritional profile of animal products derived from GMO-fed animals. Because DNA and protein are normal components of the diet that are digested, there are no detectable or reliably quantifiable traces of GMO components in milk, meat, and eggs following consumption of GMO feed.
In November 2013, after a year of continued public outcry by the science community and pressure from the agricultural biotechnology industry, Elsevier, the publisher of Food and Chemical Toxicology, announced a retraction of the paper. The publisher’s editor said he found no evidence of fraud or intentional misrepresentation of data. But wrote:
However, there is a legitimate cause for concern regarding both the number of animals in each study group and the particular strain selected. The low number of animals had been identified as a cause for concern during the initial review process, but the peer review decision ultimately weighed that the work still had merit despite this limitation. A more in-depth look at the raw data revealed that no definitive conclusions can be reached with this small sample size regarding the role of either NK603 or glyphosate in regards to overall mortality or tumor incidence. Given the known high incidence of tumors in the Sprague-Dawley rat, normal variability cannot be excluded as the cause of the higher mortality and incidence observed in the treated groups.
Séralini supporters, including a group of scientists and anti-GMO groups, attacked the retraction, accusing the journal of bowing to pressure from Monsanto. They argued that the journal held the Séralini study to a higher standard than other similarly inconclusive works. The Séralini-led European Network of Scientists for Social and Environmental Responsibility (ENSSER), whose deputy chairman is co-author of the French study and whose membership is a ‘Who’s Who’ of anti-biotechnology scientists, released a statement calling the retraction “a severe blow to the credibility and independence of science, indeed a travesty of science. … The conclusiveness of their data will be decided by future independent science, not by a secret circle of people.”
Claire Robinson, an editor with GM Watch, wrote:
It is important that scientists do not overstate their findings or draw conclusions that are not justified by the data, but Prof Séralini’s paper does not do this. Because Prof Séralini’s study was a chronic toxicity study and not a full-scale carcinogenicity study, which normally requires larger numbers of rats, he conservatively did not do a statistical analysis of the tumours and mortality findings. Instead he simply reported them, without drawing definitive conclusions. This is in line with the OECD chronic toxicity protocol, which requires that any “lesions” (including tumours) observed are recorded.
A modified version of the retracted paper was republished in June 2014 in Environmental Sciences Europe, a journal that charges researchers to publish their studies. It was not peer reviewed. [An analysis of the study here]. This set off another round of debates, with scientists generally agreeing that the nearly identical republished paper suffered the same flaws as the original. David Vaux, medical researcher at the Walter and Eliza Hall Institute in Australia wrote:
Instead of performing new experiments, in which more control animals were included, the animals were randomised and treated in an unbiased and blinded fashion, the results analysed with robust statistics, and the full dataset provided in the supplementary material, the authors have repackaged the same data as before, but have found a journal with lower standards for publication.
Séralini has continued to publish studies attempting to demonstrate the dangers of GMOs and glyphosate. In 2014, Séralini and his team published a study in BioMed Research International claiming that pesticides were more toxic than regulatory bodies previously thought. The study prompted Ralf Reski, one of the editors of the journal in which it was published, to resign. Reski said, “I do not want to be connected to a journal that provides [Séralini] a forum for such kind of agitation.”
In July 2015, Séralini was part of a team of researchers that published a study in PLOS One about the presence of toxic levels of environmental contaminants in the commercial diets of laboratory rodents [Analysis of the study here]. They argued that the presence of these pesticides and other contaminants make it difficult to use control groups in animal feeding trials:
Efforts towards safer agricultural practices and better control of environmental contaminants have to be made in order to feed laboratory rodents with healthy diets. This will not only improve the reliability of toxicity tests, but also the value of animal feeding trials in biomedical research.
The findings were rejected by the EFSA:
There are several limitations with the methodological approach used by the authors, including insufficient information about the test material and methodology used, incomplete reporting of the data, and inappropriate interpretation of legislation and results…In conclusion, no new scientific elements were provided that would impact on the validity of regulatory feeding tests in the EU.
Séralini’s January 2016 paper purportedly showing that the first commercialized GMO corn in Europe, grown from 1997-2002, was “toxic to animals over the long term” was published in another pay-for-play journal, Scholarly Journal of Agriculture Science. It states that it “was not designed as a scientific experiment,” yet it concludes that GMO corn (which is no longer available in the European market) likely played a role in the poor health of dairy cows.
A July 2016 paper published in a fringe open source journal, BMC Complementary and Alternative Health, claims to demonstrate the protective effects of Digeodren, a homeopathic product made by Sevene Pharma. The study, funded by Sevene, a longtime contributor to the French scientist’s research and public relations efforts, concludes that Digeodren can reverse the toxic effects of prolonged exposure to glyphosate. The popular herbicide is not considered by regulators to be particularly toxic or unsafe when used correctly.
Conflict of interest concerns aside, critics took aim at the premise of the study, which is based on the results of his discredited 2012 work. Others criticized the study’s controls and challenged the dosages used. Steve Savage, plant pathologist and genetics consultant, told the Genetic Literacy Project in an email:
The dose is absurd. They gave the animals the equivalent of what could be in the spray tank including the surfactants and the a.i. (active ingredients). If glyphosate or its AMPA metabolite ever end up in a food, it is at extremely low concentrations and never with the surfactant. Unless you were a farmer or gardener who routinely drinks from the spray tank over 8 days, this study is meaningless.
Much of this work, which often appears in scientifically marginal pay-for-play journals, has been widely criticized by other scientists and rejected by regulatory agencies around the world over the methodologies used and his selective presentation of data. Séralini’s supporters argue that he has been unfairly targeted by the agriculture industry and its boosters.
Related GMO FAQs
- Are GMOs safe?
- Are most GMO safety studies funded by industry?
- Do GMOs cause hidden health problems, like allergies or autism?
- Is glyphosate (Roundup) dangerous?
- What does it take to bring a new GM product to market?
- Can water protect you from glyphosate ‘poisoning’? Gilles-Eric Séralini’s homeopathy “detox” hoax, Andrew Porterfield, September 27, 2016
- Global scientists assess homeopathy-funded Séralini study claiming all GMO tests ‘contaminated,’ July 2, 2015
- Ethics debate intensifies over retraction of flawed Séralini GMO rat study, Jon Entine, January 15, 2014
- Anti-GM corn study reconsidered: Séralini finally responds to torrent of criticism, Jon Entine | November 19, 2012
- Turning point from the botched French maize study: GM opponents look like climate deniers, Jon Entine, September 28, 2012
- Gilles-Éric Séralini: Activist professor as the face of the anti-GMO industry, Biotech Gallery
• Laboratory Rodent Diets Contain Toxic Levels of Environmental Contaminants: Implications for Regulatory Tests, Robin Mesnage, Gilles-Eric Séralini, et al., PLOS One, July 2, 2015
• Seralini Rat Study Revisited, Andrew Kniss, Control Freaks, July 3, 2014
• Retracted Roundup-fed rat research republished, Nathanael Johnson, Grist, July 1, 2014
• Séralini study is given new life, but where’s the new data?, David Vaux, The Conversation, June 25, 2014
• Republished study: long-term toxicity of a Roundup herbicide and a Roundup-tolerantgenetically modified maize, Gilles-Eric Séralini, et al., June 24, 2014
• An anti-GMO article rises from the grave, Ian Musgrave, The Conversation, June 24, 2014
• Paper claiming GM link with tumours republished, Barbara Casassus, Nature, June 24, 2014
• 150 scientists condemn retraction of Séralini study as bow to commercial interests, End Science Censorship, March 4, 2014
• Séralini Threatens Lawsuit In Wake Of Retraction Of Infamous GMO Cancer Rat Study, Jon Entine, Forbes, November 29, 2013
• Journal retraction of Séralini study is illicit, unscientific, and unethical, Claire Robinson, GMWatch, November 27, 2013
• Controversial GMO Study By Gilles-Eric Seralini Retracted, Kate Kelland, Reuters, November 28, 2013
• Elsevier Announces Article Retraction from Journal Food and Chemical Toxicology, Elsevier, November 28, 2013
• Study says genetically modified corn causes tumors, but other scientists skeptical about research, Michelle Castillo, CBS News, September 21, 2012
• Why I think the Seralini GM feeding trial is bogus, Andrew Kniss, Control Freaks, September 19, 2012