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Presently, it is widely estimated that between 60 and >90 percent of most staples (corn, rice, soybeans, sugar beets, and so forth and so on) in the American food supply are genetically modified. For instance, 80 to 90 percent of all corn grown in the US is “Roundup Ready,” meaning that it is genetically modified to be resistant to the Monsanto weed killer Roundup. Moreover, many GMOs contain more than one implanted gene; corn can and is modified to be resistant to Roundup along with, say, the corn bore. Non-staple foods, such as cucumber, peas and tomatoes, increasingly are modified, as well. With GMOs having such an extensive presence in the American food chain, most of us would assume that over the years there have been detailed independent tests confirming the safety of GMOs for both those consuming these foods and the environment. Unfortunately, anyone making this assumption would be wrong. As one recent literature review notes, “the risk assessment of GM foods in general, and crops in particular for human nutrition and health, has not been systematically performed as indicated in the scientific literature.”1

The failure to perform adequate risk assessments on GMOs, including a lack of independent non-company sponsored research, was brought into stark relief recently with the case of Gilles-Eric Séralini, who led a French team in studying animals fed Monsanto’s Roundup Ready corn and discovered increased mortality and more tumors in the active groups than in a control group.2 Although the study was greeted by a storm of criticism, it also has enjoyed considerable support. Nevertheless, shortly after the journal Food and Chemical Toxicology hired as a reviewer a former Monsanto employee who previously published papers touting the safety of GMOs, the journal decided to withdraw the paper. No fraud or intentional misrepresentation, plagiarism or incompetence was found to characterize the Séralini study, meaning that none of the classic grounds for withdrawing a published scientific paper have been found or even asserted. Indeed, the journal admits this and states in a press release, “the results presented (while not incorrect) are inconclusive.”3 One might be forgiven for noting that inconclusive results are not grounds for withdrawing a published paper.

Actually, a great many scientists have not been forgiving towards the journal or its new editor, Richard E. Goodman, who retains his connections to biotech and agrochemical companies’ industry-sponsored organizations, such as the International Life Sciences Institute (ILSI). (ILSI, due to its industry affiliations, is barred from contributing to World Health Organization safety standards. Indeed, the revelation of her hidden association with ILSI forced the resignation of Diana Banati, at the time head of the management board at the European Food Safety Authority.) The European Network of Scientists for Social and Environmental Responsibility (ENSSER) has been particularly critical, calling the actions of the journal “a flagrant abuse of science” that will “decrease public trust in science.” The journal has violated “not only the criteria for retraction to which the journal itself subscribes, but any standards of good science.”4,5

Negative Findings Have Consequences—for Researchers
Why did the guardians of GMO orthodoxy react so negatively to the Séralini study? Because the results were so negative. The article now apparently is freely available on the Internet, and its abstract has always been freely available at PubMed and elsewhere. Without a doubt, the findings are damning.6

The health effects of a Roundup-tolerant genetically modified maize (from 11% in the diet), cultivated with or without Roundup, and Roundup alone (from 0.1 ppb in water), were studied 2 years in rats. In females, all treated groups died 2–3 times more than controls, and more rapidly. This difference was visible in 3 male groups fed GMOs. All results were hormone and sex dependent, and the pathological profiles were comparable. Females developed large mammary tumors almost always more often than and before controls, the pituitary was the second most disabled organ; the sex hormonal balance was modified by GMO and Roundup treatments. In treated males, liver congestions and necrosis were 2.5–5.5 times higher. This pathology was confirmed by optic and transmission electron microscopy. Marked and severe kidney nephropathies were also generally 1.3–2.3 greater. Males presented 4 times more large palpable tumors than controls which occurred up to 600 days earlier. Biochemistry data confirmed very significant kidney chronic deficiencies; for all treatments and both sexes, 76% of the altered parameters were kidney related. These results can be explained by the non linear endocrinedisrupting effects of Roundup, but also by the overexpression of the transgene in the GMO and its metabolic consequences.

The Séralini group has been roundly criticized for using too few animals per arm and using the wrong animal model. Curiously, Séralini, in fact, had followed almost exactly the protocol of an animal trial conducted by Monsanto and published in the same journal, Food and Chemical Toxicology, eight years earlier—the same number of animals per arm and the same rat species (Sprague-Dawley). Here are some differences between the two studies along with a couple of responses to criticisms:

  1. Séralini followed his animals for two years rather than 90 days
  2. Séralini carefully purified the chow of his animals so that non-GMO rat chow was, in fact, non-GMO, whereas with the earlier study by Monsanto it appears that this caution was not exercised.
  3. In response to the claim that too few animals were found per arm, it is noted that this Séralini was a general long-term toxicology study using the same model normally suggested by various national and international bodies for this type of research and for such studies, 10 animals is acceptable. Very large numbers of animals are used in dedicated cancer studies.
  4. The findings of this Séralini study were sufficient for European regulators to set aside three million euros to reproduce the study using larger numbers of animals.

As has been noted by others, the journal Food and Chemical Toxicology belongs to a professional organization that directly provides the only three reasons recognized for forcibly with-drawing already published articles, to wit, (1) findings unreliable due to misconduct, (2) plagiarism or redundant publication, and/or (3) unethical research / data fabrication. The journal itself admits that none of these three factors applies to the Séralini paper. One succinct overview of the controversy points out that this is the second negative article on bioengineering to be retracted by the journal since Goodman became an editor, implying scientific censorship.7

Findings suggesting long-term toxicity of GMOs, such as the toxicities uncovered by Séralini, are not unique. Perhaps the most famous case is that of GM potato toxicity found in a rat model by Arpad Pusztai in the United Kingdom. Pusztai at the time was considered a world authority on GMOs and until his negative findings with the engineered potatoes he was a darling of the bioengineering world. (The laboratory animals consuming the test materials developed damage to the gastrointestinal tract along with other changes.) After his revelations regarding the side effects of the potatoes, however, his career was trashed through a systematic campaign. Readers who are interested in pursuing the history of opposition to GMOs and the consequences might start with the film, The World According to Monsanto, by Marie-Monique Robin. Moreover, it should be kept in mind that the holders of many of the patents on genetically modified features refuse to allow independent third party researchers from conducting studies on their seeds. Similarly, many growers’ contracts prevent them from providing seeds or feed grains to researchers (giving, selling, providing seed for growth of the food, etc.). These restrictions obviously are designed to prevent independent investigations. As one observer has asked rhetorically, “Any study you want to do with these engineered crops, you need to get the company’s permission… Could you imagine if tobacco research was only done when the tobacco companies had the final say?”8

Despite such scorched earth responses from the bioengineering industry towards scientists who publicize toxicity and other findings involving GMOs, it remains the case that numerous studies have found damage to the liver, kidneys, gastrointestinal tract and other organ systems in animals fed grains engineered to be highly tolerant glyphosate (Roundup Ready), the leading chemical weed killer.9 Quite recently, a US/Australian study on pigs consuming GM and non-GM corn and soy found “significantly higher rates of ‘severe’ stomach inflammation, as well as an average of 25 percent heavier uteri in relation to body weight… 23 GM pigs had severely inflamed stomachs, while only 9 non-GM did.”10,11,12

But GMOs Are Natural….
Currently, there is a push to characterize genetic modification as being as “natural” as the plant breeding done for hundreds of years. However, normal or “natural” breeding techniques change the genetic code found in the nucleus of the cell, whereas genetic modification typically plants genes in the cytoplasm of cells or uses other techniques that do not firewall the implanted genes.

This is horizontal gene transfer (also called horizontal inheritance) as opposed to the vertical gene transfer found in natural reproduction.

There are consequences. For instance, leaving aside the well documented damage to soil quality, the glyphosate resistance engineered into Roundup Ready crops can be—and is—passed onto plants growing in the same vicinity. The horror of Roundup-resistant weeds now sprouting everywhere not only is that they are resistant to Roundup, but that many of these weeds are showing unexpected characteristics, such as growing faster and larger, having thick and woody stems difficult to cut with farming equipment, etc. Worse yet, the same transfer of genetic material that is happening routinely at farms raising GMOs can take place at large, especially in related species. Whether by accident or by design, the widespread planting of GMOs threatens to contaminate the remaining non-GMO forms of the plants involved throughout the entire world. In the US presently these GMOs already are planted widely: soy, corn, cotton (for oil), canola (for oil), sugar beets, zucchini, yellow squash, Hawaiian papaya and alfalfa.

Can things get worse? They certainly can. Evidence is accumulating to the effect that glyphosate, the active ingredient in Roundup, suppresses cytochrome P450 enzymes and related amino acid biosynthesis by human gut bacteria and that this action may be responsible for activating and/or increasing the virulence of a number of disease conditions.13,14 Worse yet, at least some of the genetic modifications inserted into our food crops may find their way into our own gut bacteria. As one research has put it,15

“It is now clear that horizontal transfer of GM DNA does happen, and very often. Evidence dating from the early 1990s indicates that ingested DNA in food and feed can indeed survive the digestive tract, and pass through the intestinal wall to enter the bloodstream. The digestive tract is a hotspot for horizontal gene transfer to and between bacteria and other microorganisms. ... What are the dangers of GM DNA from horizontal gene transfer? Horizontal transfer of DNA into the genome of cells per se is harmful, but there are extra dangers from the genes or genetic signals in the GM DNA, and also from the vector used in delivering the transgene(s). GM DNA jumping into genomes cause ‘insertion mutagenesis’ that can lead to cancer, or activate dormant viruses that cause diseases. GM DNA often contains antibiotic resistance genes that can spread to pathogenic bacteria and make infections untreatable. Horizontal transfer and recombination of GM DNA is a main route for creating new viruses & bacteria that cause diseases.”

Genetic modification technology is a bit like the discovery of fire: both useful and dangerous. To date, there is little or no evidence that the widespread adoption of GMOs has improved food production or has lowered most production costs. Although it may be desirable to be able to rapidly introduce new traits into crops, the hidden costs and the costs simply transferred into the future are quite real. Numerous non-industry sponsored studies have revealed potential toxicities from GMOs that need to be further studied. As several recent academic reviews have noted, up to this point there have not been adequate studies using standardized methodologies and protocols. The Affair Séralini, if nothing else, makes clear that we have been conducting an elaborate experiment on ourselves performed adequate and sometimes quite basic toxicology studies. The proper response is not to use pressure behind the scenes to force the retraction of papers guilty of no more than publishing a few inconclusive data points, but rather to conduct proper large scale trials which are independent, third party and open to protocols which critics of GMOs, not just proponents, would find to be adequate.

Above all, it is important to avoid the “well, the study was not perfect” types of arguments so often used to reject any criticisms of GMOs. Big Tobacco used precisely these types of arguments to safeguard tobacco sales against medical criticisms for, quite literally, decades. No one today can defend smoking, so why were those arguments so successful for so long? We should be extremely wary about giving GMOs the same degree of freedom from scrutiny that so long characterized smoking in this country.

  1. Domingo JL, Giné Bordonaba J. A literature review on the safety assessment of genetically modified plants. Environ Int. 2011 May;37(4):734–42.
  2. 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.
  3. Elsevier Announces Article Retraction from Journal Food and Chemical Toxicology. Press release, November 28, 2013.
  4. ENSSER Comments on the Retraction of the Séralini et al. 2012 Study.
  5. “Monsanto behind Journal’s retraction of GMO rat-cancer link” accessed at
  6. See
  7. Living on Earth, episode for December 6, 2013 found at
  8. Michael Hansen in “Scientists Debate New Study on GMO-Fed Pigs,” Food Safety News 13 June 2013 found at
  9. Domingo JL, Giné Bordonaba J. A literature review on the safety assessment of genetically modified plants. Environ Int. 2011 May;37(4):734–42.
  10. “Scientists Debate New Study on GMO-Fed Pigs,” Food Safety News 13 June 2013 found at
  11. Carman J, et al. A long-term toxicology study on pigs fed a combined genetically modified (GM) soy and GM maize diet. Journal of Organic Systems Vol. 8(1) 2013.
  12. See
  13. Samsel A, Seneff S. Glyphosate’s Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases. Entropy 2013, 15, 1416–63.
  14. See
  15. See the discussion at of 6 August 2013 with material from Dr. Mae-Wan Ho at Why GMOs Can Never Be Safe,

Dallas Clouatre, PhD

Dallas Clouatre, Ph.D. earned his A.B. from Stanford and his Ph.D. from the University of California at Berkeley. A Fellow of the American College of Nutrition, he is a prominent industry consultant in the US, Europe, and Asia, and is a sought-after speaker and spokesperson. He is the author of numerous books. Recent publications include "Tocotrienols in Vitamin E: Hype or Science?" and "Vitamin E – Natural vs. Synthetic" in Tocotrienols: Vitamin E Beyond Tocopherols (2008), "Grape Seed Extract" in the Encyclopedia Of Dietary Supplements (2005), "Kava Kava: Examining New Reports of Toxicity" in Toxicology Letters (2004) and Anti-Fat Nutrients (4th edition).