The study has been widely criticised.
Many claimed that Séralini's conclusions were impossible to justify given the statistical power of the study. Sprague-Dawley rats have a lifespan of about two years and have a high tendency to get cancer over their lifespan (one study found that over eighty percent of males and over seventy percent of females got cancer under normal conditions).[36][37][38] The Séralini experiment lasted the normal lifespan of these rats, and the longer the experiment goes, the more statistical "noise" there is - the more rats get cancer naturally, regardless of what you do to them. So for the experiment to have adequate statistical power, all the groups - control groups and test groups - would have to include at least 65 rats per group in order to sort out any experimentally caused cancers from cancers that would occur anyway - but the Séralini study had only ten per group.[34] OECD (Organisation for Economic Cooperation and Development) guidelines recommend 20 rats for chemical-toxicity studies, and 50 rats for carcinogenicity studies.[39]:5-6 In addition, if the survival of the rats is less than 50% at 104 weeks (which is likely given the Sprague-Dawley rats used in the study) the recommended number of rats is 65.[34][37][38]
Kings College London Professor Tom Sanders[40] wrote that since Sprague-Dawley rats are susceptible to mammary tumors when food intake is not restricted, data should have been provided about how much food the rats were fed (as well as the presence of fungus in the feed, another confounder). Sanders also wrote of this study, "The statistical methods are unconventional ... and it would appear the authors have gone on a statistical fishing trip."[41]
The Washington Post quoted Marion Nestle, the Paulette Goddard professor in the Department of Nutrition, Food Studies and Public Health at New York University and food safety advocate: "' can’t figure it out yet....It’s weirdly complicated and unclear on key issues: what the controls were fed, relative rates of tumors, why no dose relationship, what the mechanism might be. I can’t think of a biological reason why GMO corn should do this.....So even though I strongly support labeling, I’m skeptical of this study.'"[42] University of Calgary Professor Maurice Moloney, among others, went on record wondering why there were so many pictures in the study, and in sympathetic news reports about it, of treated rats with horrific tumors, but no pictures of the rats in the control group.[43]
Many national food safety and regulatory agencies reviewed the paper and condemned it. The German Federal Institute for Risk Assessment VP Reiner Wittkowski said in a statement, ""The study shows both shortcomings in study design and in the presentation of the collected data. This means that the conclusions drawn by the authors are not supported by the available data."[44] A joint report by three Canadian regulatory agencies also "identified significant shortcomings in the study design, implementation and reporting."[45] Similar conclusions were reached by the French HCB[30] and the National Agency for Food Safety,[46] the Vlaams Instituut voor Biotechnologie,[47] the Technical University of Denmark,[48] Food Standards Australia New Zealand,[49] the Brazilian National Technical Commission on Biosafety,[50] and the European Food Safety Authority (EFSA).[39] The conclusions of the EFSA evaluation were:
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.[39]
The European Federation of Biotechnology lobby, which counts Monsanto and other GM firms among its members,[51] called for the paper to be retracted, calling its publication a "dangerous failure of the peer-review system."[34] Six French national academies (of Agriculture, Medecine, Pharmacy, Science, Technology and Veterinarians[52]) issued a joint statement - "an extremely rare event in French science"[53] - condemning the study and the journal that published it.[52] The joint statement dismissed the study as 'a scientific non-event'.[53] The Food and Chemical Toxicology journal, an Elsevier imprint, has a full peer review process, and at least three scientists were needed to endorse the Seralini article prior to publication. The journal in question published a statement in their November 2012 issue,[3] that "the Editors have encouraged those people with concerns to write formally to the Editor-in-Chief, so that their views can be publicly aired."
In March 2013, the same journal that published the Seralini study, published a letter[54] from Erio Barale-Thomas,[55] Principal Scientist of Johnson & Johnson Pharmaceutical Research and Development and the President of the Conseil d’Administration of The Société Française de Pathologie Toxicologique (SFPT, French Society of Toxicologic Pathology[56]). SFPT is "a non governmental/non profit organization formed by veterinarians, physicians, pharmacists and biologists specialized in veterinary and toxicologic pathology. Its aim is to promote knowledge in pathology, toxicology and laboratory animal sciences for safety studies of drugs, chemicals and food products, and the role of the pathologist in the study design and data interpretation."[54] The letter criticized the Seralini study on several fronts, and concluded: "However, given this study presents serious deficiencies in the protocol, the procedures and the interpretation of the results, the SFPT cannot support any of the scientific claims drawn by the authors, and any relevance for human risk assessment. This letter presents the consensus scientific opinion of the Conseil d’Administration of the SFPT."[54]
As a result of the publication of the Séralini paper, the Belgian Federal Minister of Public Health asked the Belgian Biosafety Advisory Council (BBAC) to evaluate the paper. The BBAC was asked to "inform the Minister whether this paper (i) contains new scientific information with regard to risks for human health of GM maize NK603 and (ii) whether this information triggers a revision of the current authorisation for commercialisation for food and feed use of this GM maize in the European Union (EU)."[57] Responding to the two point mandate, the BBAC committee, whose members are drawn from the Belgian biotech Professoriat,[57] pointed out that "the long duration of this study is a positive aspect since most of the toxicity studies on GMOs are performed on shorter periods," and concluded that:
"Given the shortcomings identified by the experts regarding the experimental design, the statistical analysis, the interpretation of the results, the redaction of the article and the presentation of the results, the Biosafety Advisory Council concludes that this study does not contain new scientifically relevant elements that may lead to reconsider immediately the current authorisation for food and feed use of GM maize NK603. Considering the issues raised by the study (i.e. long term assessment), the Biosafety Advisory Council proposes EFSA urgently to study in depth the relevance of the actual guidelines and procedures. It can find inspiration in the GRACE project[58] to find useful information and new concerted ideas."[57]:9
