Summary answer:

No mandatory protocols exist for GM food safety testing. Industry is free to design its own tests, which are generally weak. Séralini designed a protocol to test the long-term health effects of a GMO and its associated pesticide. His protocol was the first to differentiate between the effects of the GMO and those of the pesticide.


Detailed answer:

Critics of Séralini’s study complain that it does not follow internationally standardized protocols set by the Organisation for Economic Cooperation and Development (OECD).

But in fact, no such protocols for testing GM foods have ever been set by the OECD, the European Food Safety Authority (EFSA), or any other body. This is in spite of repeated demands for standardized protocols by scientists and civil society groups, who have criticized the weakness of industry studies submitted in support of applications for GM crop approvals.

Industry and academic scientists researching the health effects of GMOs are free to design their own experiments. So it is absurd to argue that Séralini has broken some fundamental rule in his protocol design. There is no rule.

The European Food Safety Authority (EFSA) has listed some OECD protocols that it deems “relevant” to GM food safety testing, but EFSA does not require or even recommend any particular protocol.5 The OECD protocols that EFSA lists vary widely in design.

In practice, industry has often adapted OECD protocol 408, a subchronic 90-day rodent feeding trial designed for testing chemicals, for its safety tests on GM foods.6

However, industry has not kept to the protocol laid down in OECD 408, but only used it as a starting point. The number of animals used and analyzed, the endpoints (effects) tested for, the control groups included, the diets used, and which data is reported, have not been in accord with OECD 408 and vary widely between experiments.

Often, industry has adapted OECD 408 in the direction of less rigour. For example, OECD 408 requires a minimum of three doses in order to establish a dose-response relationship, but Monsanto’s tests on GMOs have used only two.2 3 4 Since you can draw a straight line between any two points on a graph, a dose-response relationship cannot be established with only two doses. A third dose is needed in order to draw any conclusions about dose-related effects. This is the reason why Seralini included a third feeding dose of GM maize and of Roundup in his study.

Why are mandatory protocols for industry tests on GMOs important?

The lack of mandatory standardized protocols for industry studies on GMOs allows selection of data, and therefore bias, to creep in. For example, if a test on one species of animal shows ill effects from eating the GM food, a test on a less sensitive animal could be submitted to regulators instead. If one type of ill effect is found, that endpoint could be omitted from the submitted data and other endpoints, where no problem was found, included instead.

In an example of selective reporting of results, Monsanto, in some of its 90-day feeding trials on GMOs (including the one on NK603 maize), weighed the organs of all 20 animals in each test group but reported blood and urine measurements from only ten out of 20. The Monsanto researchers gave no information about why only ten out of the 20 animals were analyzed and how those ten were selected.23 4 Did they analyze the blood and urine chemistry of only the rats with the healthiest organ weights? Such selective reporting invalidates Monsanto’s data because of the potential for bias.

The way to avoid such bias is to set rigorous, internationally agreed, and mandatory protocols for testing GM foods. In the past, attempts by independent (non-industry) scientists such as Arpad Pusztai to design such protocols have been deliberately obstructed. Pusztai’s government-funded experiments with GM potatoes in the 1990s were intended to establish protocols for testing GM foods for safety. But his experiments and career were abruptly terminated in 1998 after he went public with his findings that GM potatoes caused toxic effects in rats. Pusztai came under the same type of vicious attacks as are now being directed at Séralini.7 However, Pusztai’s findings passed peer review and were published.8

Double standards used to evaluate GMO safety tests

There has been widespread use of double standards to attack Séralini’s study. Séralini built on an experimental protocol used by industry in its 90-day safety tests on GMOs,23 4 but his experiment was longer in duration and tested for more effects.

Séralini’s critics did not complain about the design and methodology of the industry studies when the conclusion was that the GMO was safe. Yet they condemn Séralini’s study, which is of a more rigorous design but came to the opposite conclusion: that the GMO and Roundup are not safe.

In an open letter to Le Monde newspaper, 140 French scientists condemned the double standards used by Séralini’s critics:

“It is remarkable to see these same experts accept (even if they sometimes criticize) an experimental protocol when it gives results that are in line with the acceptance of a technique [GM] and demolish it so ardently when the results are in the opposite direction. This is in our opinion totally contrary to all scientific ethics. We therefore affirm that if the findings of larger scale experiments [like Séralini’s] are open to question, then this [scepticism] also applies to the tests that were used to approve all the transgenic crops currently on the market.”9

In an example of these double standards at work, BASF’s Amflora GM potato was authorized in the EU on the basis of a 90-day rat feeding study using only five rats per sex per group – half the number stipulated by the OECD protocol 408, on which most industry studies on GMOs are based, and half the number that Séralini used.

In BASF’s experiment, just ten rats were fed the GM potato, which only made up 5% of their diet – too small a proportion to reliably show toxic effects.10

Even so, the test revealed an increased number of thyroid cysts in the GM-fed male rats. But the European Food Safety Authority (EFSA) dismissed the finding as “likely to be due to natural variability”10 – in spite of the small number of rats used – and the potato was authorized for commercialization.

So EFSA found this small number of rats sufficient to prove safety in an industry experiment, but twice the number of rats in Séralini’s experiment insufficient to prove risk.

Also, EFSA criticized Séralini for not following OECD protocols,11 even though none exist for GM food safety testing, but accepted BASF’s study in spite of the fact that it departs from any OECD protocol cited by EFSA as relevant to GM safety testing.5

EFSA routinely uses such double standards in evaluating studies on GMO safety. The German research organisation Testbiotech pointed out that EFSA criticized Séralini’s study for not conforming to OECD protocols but routinely accepts non-OECD-compliant tests carried out by industry as proof of GMO safety:

“EFSA does not apply OECD standards to subchronic, 90 day feeding studies when these are prepared by industry and do not show health effects from consuming genetically engineered foods. In contrast, the OECD standards have been used by EFSA to attack the research of Séralini et al., 2012.”12

The European Network of Scientists for Social and Environmental Responsibility (ENSSER) has also condemned EFSA’s double standards in evaluating GMO safety tests.13

Clearly, this biased system favours industry at the expense of public health.


EFSA’s stance on GM safety testing threatened by Séralini’s findings

While the industry animal feeding studies routinely carried out on GMOs for regulatory purposes are inadequate, the European Food Safety Authority (EFSA) has argued that even these should not be mandatory. EFSA added that if such tests are carried out, a duration of 90 days is sufficient to see any long-term effects that might result from GM foods.5

Séralini’s findings show that this stance is not scientifically justified, as the tumours, premature deaths and organ damage were only visible after 90 days. The first tumours appeared only 4-7 months into the study, with ill-effects escalating and peaking during the second year.

If Séralini’s results were taken seriously, they would demolish long-standing and fundamental policies on GM foods held by regulatory bodies such as EFSA.

In the case of NK603, EFSA has issued opinions claiming that it is as safe as non-GM maize.14 Again, Séralini’s study shows that this is not valid. Given EFSA’s investment in the assumed safety of NK603 maize and other GMOs, it is not surprising that it denies the validity of Séralini’s findings.

Why so much talk of OECD protocols?

We include this detailed discussion of OECD protocols not because they represent the best, most up-to-date, or reliable science. They do not.

We include it because there is an increasing tendency on the part of industry affiliates and some regulators to dismiss the findings of any study by independent scientists on the grounds that it does not conform to OECD protocols. The European Food Safety Authority (EFSA) dismissed Séralini’s study largely on the grounds that it does not conform to OECD protocols,11 though EFSA has accepted as proof of the safety of GM foods industry studies that fall far short of standards set in OECD protocols.

For example, industry studies have tested only two doses of the GM food23 4 instead of the three demanded by OECD subchronic protocol 408,6 meaning that no dose-response relationship can be established in any effects found. Séralini’s study, in contrast, used three doses, as recommended by the OECD.

Séralini also included additional toxicological measurements, such as hormonal effects, that exceeded the standards set by the OECD and that were not carried out in the industry studies. In addition, Séralini’s study followed up over a long-term period the signs of toxicity found in Monsanto’s 90-day study.

So Séralini’s study met higher scientific standards than those of the OECD protocols and the industry studies. Yet EFSA rejected Séralini’s study on grounds that they do not conform to OECD protocols, while accepting industry studies that also do not conform to OECD protocols.

A report on these double standards by the German scientific organisation Testbiotech concluded:

“EFSA does not apply OECD standards to subchronic, 90 day feeding studies when these are prepared by industry and do not show health effects from consuming genetically engineered foods. In contrast, the OECD standards have been used by EFSA to attack the research of Séralini et al., 2012.”12

OECD protocols are a set of internationally agreed methods that industry must follow in testing its products and substances for regulatory purposes. They were designed by industry and government representatives for industry tests, not for independent scientists. The aim was twofold:

  • To reduce the testing burden on industry: industry only has to do one set of tests to gain regulatory authorization in every country that has signed up to the OECD system
  • To ensure a minimum standard for industry tests.

Far from being a hallmark of good science, OECD protocols are a compromise between what is affordable to industry and what is acceptable to regulators.

Few independent (non-industry) researchers use OECD protocols, because they do not find them useful. OECD protocols have come under increasing criticism for being rigid, limited, decades out of date, and insensitive. They often miss important toxic effects such as low-dose effects and effects at vulnerable life stages, such as development in the uterus, infancy, and old age.

A related concept that is also used by industry and some regulators to dismiss the findings of independent scientific studies is Good Laboratory Practice (GLP). Like OECD protocols, GLP rules are not a hallmark of good science. They are a set of laboratory management rules brought in by government regulators in the 1970s and 1980s to combat widespread industry fraud in the testing of chemicals for regulatory purposes.

In practice, OECD protocols and GLP rules are often misused as a shield to protect industry’s risky products from the inconvenient findings of independent science.

For more on OECD/GLP and related issues, see:

  • Myers, J. P., F. S. vom Saal, et al. (2009). Why public health agencies cannot depend on good laboratory practices as a criterion for selecting data: The case of bisphenol A. Environ Health Perspect 117: 309-315.
  • Soffritti, M., F. Belpoggi, et al. (2007). Life-span exposure to low doses of aspartame beginning during prenatal life increases cancer effects in rats. Environ Health Perspect 115(9): 1293-1297.
  • Tweedale, A. C. (2011). Uses of Good Laboratory Practices by regulated industry and agencies, and the safety of bisphenol A. J Epidemiol Community Health 65: 475-476.
  • Vandenberg, L. N., T. Colborn, et al. (2012). Hormones and endocrine-disrupting chemicals: Low-dose effects and nonmonotonic dose responses. Endocr Rev 33: 378-455.
  • Vom Saal, F. S. and C. Hughes (2005). An extensive new literature concerning low-dose effects of bisphenol A shows the need for a new risk assessment. Environ Health Perspect 113: 926-933.




1.         de Vendomois JS, Roullier F, Cellier D, Séralini GE. A comparison of the effects of three GM corn varieties on mammalian health. Int J Biol Sci. 2009; 5(7): 706–726.

2.         Hammond B, Dudek R, Lemen J, Nemeth M. Results of a 13 week safety assurance study with rats fed grain from glyphosate tolerant corn. Food Chem Toxicol. Jun 2004; 42(6): 1003-1014.

3.         Hammond B, Lemen J, Dudek R, et al. Results of a 90-day safety assurance study with rats fed grain from corn rootworm-protected corn. Food Chem Toxicol. Feb 2006; 44(2): 147-160.

4.         Hammond BG, Dudek R, Lemen JK, Nemeth MA. Results of a 90-day safety assurance study with rats fed grain from corn borer-protected corn. Food Chem Toxicol. Jul 2006; 44(7): 1092-1099.

5.         European Food Safety Authority (EFSA) GMO Panel Working Group on Animal Feeding Trials. Safety and nutritional assessment of GM plants and derived food and feed: The role of animal feeding trials. Food Chem Toxicol. Mar 2008; 46 (Suppl 1): S2-70.

6.         Organisation for Economic Cooperation and Development (OECD). OECD guideline no. 408 for the testing of chemicals: Repeated dose 90-day oral toxicity study in rodents: Adopted 21 September 1998. 1998.

7.         Rowell A. Don’t Worry, It’s Safe to Eat. London, UK: Earthscan Ltd; 2003.

8.         Ewen SW, Pusztai A. Effect of diets containing genetically modified potatoes expressing Galanthus nivalis lectin on rat small intestine. Lancet. Oct 16 1999; 354(9187): 1353-1354.

9.         Andalo C, Chercheuse AHS, Atlan A, Auclair D, Austerlitz F, Barot S. Science et conscience [Science and conscience]. Le Monde. 14 November 2012.

10.      European Food Safety Authority (EFSA). Opinion of the Scientific Panel on Genetically Modified Organisms on an application (Reference EFSA-GMO- UK-2005-14) for the placing on the market of genetically modified potato EH92-527-1 with altered starch composition, for production of starch and food/feed uses, under Regulation (EC) No 1829/2003 from BASF Plant Science. EFSA Journal. 2006; 2006(324): 1-20.

11.      European Food Safety Authority (EFSA). Review of the Séralini et al. (2012) publication on a 2-year rodent feeding study with glyphosate formulations and GM maize NK603 as published online on 19 September 2012 in Food and Chemical Toxicology. EFSA Journal. 2012; 10(10): 2910.

12.      Then C. The European Food Safety Authority: Using double standards when assessing feeding studies: A Testbiotech background. 30 October 2012.

13.      European Network of Scientists for Social and Environmental Responsibility (ENSSER). Questionable biosafety of GMOs, double standards and, once again, a “shooting-the-messenger” style debate. 5 October 2012.

14.      European Food Safety Authority (EFSA). Opinion of the Scientific Panel on Genetically Modified Organisms on a request from the Commission related to the safety of foods and food ingredients derived from herbicide-tolerant genetically modified maize NK603, for which a request for placing on the market was submitted under Article 4 of the Novel Food Regulation (EC) No 258/97 by Monsanto (QUESTION NO EFSA-Q-2003-002): Opinion adopted on 25 November 2003. EFSA Journal. 2003; 2003(9): 1–14.


Sources of criticism:


European Food Safety Authority

BfR (German federal institute for risk assessment)

Science writer Declan Butler, writing in Nature journal