GM maize is not safe to eat

The most in-depth GM-food safety study to date has been published.

It represents a landmark on three counts:
  • It's what GM-free Scotland and similarly concerned people have been asking for since the 1990s
  • The study is unprecedented in scale, control of variables, exposure time, and the breadth of parameters measured
  • And, it confirms that existing GM food safety testing protocols are totally inadequate to identify harm.
What was found was a shocking catalogue of chronic ill-health in all animals exposed to test diets. With regard to the disturbances in renal function alone, the lead author, Eric-Gilles Séralini, said “Any doctor would panic for a patient in this case.”

The study was a long-term feeding trial of Monsanto's NK603 Roundup Ready maize which is approved for import into the EU. It was designed to distinguish between adverse effects arising from the GM maize itself, from the Roundup herbicide which the maize accumulates, and from both consumed together. (See details below.)

The experiment

The experiment involved 200 rats assigned to 10 groups of 20, consisting of 10 males and 10 females.
Standard laboratory rats of a strain widely used as a surrogate for humans were used.

The maize formulated into the rats' diet consisted of NK603 maize grown with or without Roundup spraying, or a genetically equivalent conventional maize, all grown at the same site.

The rats' health was recorded until they died of natural causes at around 2 years, or until they were euthanised to prevent undue suffering due to ill-health.

Each group received a different diet:
  • The test groups were fed Roundup-treated NK603 maize at three diet-relevant concentrations, thus modelling one common GM maize as actually eaten.
  • To control for the effects of the genetic transformation, further groups were fed unsprayed NK603 at three concentrations.
  • To control for the effects of the herbicide treatment, further groups were given the conventional maize, and had Roundup added to their drinking water at three environmentally-relevant concentrations.
  • One group, the control, was fed the conventional maize
In all, 80 rats were fed conventional maize, 120 rats were fed GM maize, and 120 rats were exposed to Roundup.

Whether the rats received GM maize, Roundup or both together, multiple problems were observed. For example, blood chemistry and tissue pathology revealed sex hormone imbalance, pituitary dysfunction, kidney failure, and liver-function impairment.

The rat strain used has a known tendency to develop tumours, especially mammary tumours, in old age. Since experiments are normally short-term and use young healthy animals, tumours are nor see, but in this life-long experiment some tumour development was expected. However, it was found that the numbers of tumours per individual were significantly greater (in some cases more than double) in most test groups, and in all female groups. Of even more concern, was the observation of widespread premature tumour appearance in test groups (the fastest took only four months, which is early adulthood in a rat).

Roundup has been linked to DNA damage, cancer, developmental abnormalities, micronutrient interference, and endocrine disruption, while NK603 has never been studied in any depth beyond its short-term livestock feeding value. It was very surprising to see that adverse effects were equally evident in all groups fed GM maize both with and without Roundup.

Few of the observed adverse effects were dose-related as would be the case if a specific toxin were targetting specific metabolic pathways or structures. Rather, the picture is of the experimental animals falling victim to an interacting cocktail of low-level toxins plus endocrine- and micronutrient-disruption: a threshold is present above which the cumulative stresses of subtle but harmful elements the diets trigger physiological failure. In such circumstances, individual weaknesses dictate actual susceptibility, and a variety of diseases can present. On the level of a population, the effect is a steady accumulation of disease over time with marked ill-health in old age.

Another possibility considered by the authors is that harm may arise from novel foods in addition to nutritional deficiencies, toxins, and hormone disruption. Substances thought to exert a protective effect on the kidney were found to be low in NK603. Only long-term feeding studies will ever pick up this class of harm.

Notably, life-length tended to increase in males given test feed. This isn't a sign of their better health because laboratory rats have a reduced life-span due to over-availability of food. The long-lived test rats were sick and losing weight. Life-span by itself is clearly not a measure of food safety.

Due to the huge amount of data collected during this study, not all of them could be presented in one paper. It is, therefore, planned to be the first of several.

The authors concluded: “Altogether, the significant biochemical disturbances and physiological failures documented in this work confirm the pathological effects of these GMO and (Roundup) treatments in both sexes, with different amplitudes. We propose that agricultural edible GMOs and formulated pesticides must be evaluated very carefully by long term studies to measure their potential toxic effects.”


The outcome of this study is of major concern, especially to vulnerable sectors of the population and to women with any risk of breast cancer.

Worse, it delivers a major health warning to all people in places polluted by Roundup: in other words most rural areas in the developed world, areas which grow GM crops, and many recreational sites such as parks and playgrounds.

The cause of the health problems arising from NK603 remains to be clarified. They may be due to side-effects of the protein produced by the artificial gene, or to side-effects arising from some other induced aberration in gene expression in the GM plant. Whatever the cause, the same thing may well be present in some form in all Roundup-Ready crops. People in areas where such crops form the staple diet are very much at risk.

Needless to say, as soon as the news broke on this study, the political fallout began raining down, see POLITICAL FALLOUT FROM UNSAFE GM MAIZE - News, October 2012 .

As Guardian science writer, John Vidal, said the “Study linking GM maize to cancer must be taken seriously by regulators”. Start demanding this NOW because the pro-GM lobby is doing everything within its power to divert attention, confuse the public, and cover up the evidence.

  • Gilles-Eric Séralini et al., 2012, Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize, Food and Chemical Toxicology, on-line August 2012
  • Author defends Monsanto GM study as EU orders review, Reuters, 20.09.12
  • John Vidal, Study linking GM maize to cancer must be taken seriously by regulators, Guardian 28.09.12
  • Elinor Zuke, Monsanto Roundup weedkiller and GM maize implicated in 'shock' new cancer study, The Grocer, 19.09.12
  • Monsanto's attempt to “disappear” tumours is invalid, Earth Open Source briefing, 26.09.12
  • Elinor Zuke, Scientists shrug off attacks on Monsanto GM/cancer trial, The Grocer 20.09.12
  • FAQ - From CRIIGEN research team,, 22.09.12

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