Over the past couple of weeks, I have discussed a study by Gilles-Eric Séralini et al. published in Food and Chemical Toxicology that concluded that glyphosate-resistant NK603 GMO corn developed by Monsanto causes severe diseases such as tumors in rats. Of course, the study was picked up by many anti-science groups and broadcast widely as “GMO foods cause cancer.”
Except, the study really was badly done. Read about my deconstruction of the study here. And read how GMO’s have become the “global warming denialism” of the left. The study was ridiculed widely in science and skeptics blogs. A new article in Nature News summarized the criticism of Séralini et al.:
The biggest criticism from both reviews is that Séralini and his team used only ten rats of each sex in their treatment groups. That is a similar number of rats per group to that used in most previous toxicity tests of GM foods, including Missouri-based Monsanto’s own tests of NK603 maize. Such regulatory tests monitor rats for 90 days, and guidelines from the Organisation for Economic Co-operation and Development (OECD) state that ten rats of each sex per group over that time span is sufficient because the rats are relatively young. But Séralini’s study was over two years — almost a rat’s lifespan — and for tests of this duration, the OECD recommends at least 20 rats of each sex per group for chemical-toxicity studies, and at least 50 for carcinogenicity studies.
Moreover, the study used Sprague-Dawley rats, which both reviews note are prone to developing spontaneous tumours. Data provided to Nature by Harlan Laboratories, which supplied the rats in the study, show that only one-third of males, and less than one-half of females, live to 104 weeks. By comparison, its Han Wistar rats have greater than 70% survival at 104 weeks, and fewer tumours. OECD guidelines state that for two-year experiments, rats should have a survival rate of at least 50% at 104 weeks. If they do not, each treatment group should include even more animals — 65 or more of each sex.
“There is a high probability that the findings in relation to the tumour incidence are due to chance, given the low number of animals and the spontaneous occurrence of tumours in Sprague-Dawley rats,” concludes the EFSA report. In response to the EFSA’s assessment, the European Federation of Biotechnology — an umbrella body in Barcelona, Spain, that represents biotech researchers, institutes and companies across Europe — called for the study to be retracted, describing its publication as a “dangerous case of failure of the peer-review system”.
The numerous issues relating to the design and methodology of the study as described in the paper mean that no conclusions can be made about the occurrence of tumours in the rats tested.
Therefore, based on the information published by the authors, EFSA does not see a need to re-examine its previous safety evaluation of maize NK603 nor to consider these findings in the ongoing assessment of glyphosate.
On the basis of the publication, the BfR has come to the conclusion that the authors’ main statements are not sufficiently corroborated by experimental evidence. In addition, due to deficiencies in the study design and in the presentation and interpretation of the study results, the main conclusions of the authors are not supported by the data.
- Séralini GE, Clair E, Mesnage R, Gress S, Defarge N, Malatesta M, Hennequin D, de Vendômois JS. Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. Food Chem Toxicol. 2012 Nov;50(11):4221-31. doi: 10.1016/j.fct.2012.08.005. Epub 2012 Sep 19. PubMed PMID: 22999595.
- A study of the University of Caen neither constitutes a reason for a re-evaluation of genetically modified NK603 maize nor does it affect the renewal of the glyphosate approval. Bundesinstitut für Risikobewertung (BfR). October 1, 2012.
- EFSA Press Release: EFSA publishes initial review on GM maize and herbicide study. European Food Safety Authority. October 4, 2012.