1.1—Pusztai’s Flawed Claims

Based on flawed and inconclusive experiments with rats, Arpad Pusztai makes claims about genetically engineered potatoes.

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

A panel of experts, the Royal Society and food-safety scientists in regulatory agencies around the world, all have concluded that the study does not demonstrate that the GM potatoes were unsafe in any way.  Although Pusztai travels around the globe fear-mongering about the dangers of GM crops, it is ironic that even if his study were correct, it would only prove that those specific potatoes were unsafe, and not that all GM crops are unsafe as he seems to be claiming.  For the record, the potatoes in question were a research project; they were never submitted to regulators and they were never commercialized.

  1. Experts say no scientific conclusion can be made from the work.  Two separate expert panels reviewed this research and concluded that both the experimental design and conduct of the experiments were fatally flawed, and that no scientific conclusion should be drawn from the work (Royal Society 1999; Fedoroff and Brown 2004).  Smith fails to tell us this.  When The Lancet published the work, editors there published a critical analysis in the same issue (Kuiper 1999).  The media has devoted little time and space to these critical analyses of Pusztai’s claims.
  2. No differences were seen between the groups of animals.  Experts who reviewed the data stated that there were no meaningful differences between control and experimental groups, that the same cellular differences could be seen in all groups—GM-fed or not—and that too few animals were used to allow statistical significance to be achieved (Royal Society 1999)
  3. Flawed study design and improper diets doomed the study to failure. The diets were protein-deficient and different groups of rats received different diets. Some rats were fed raw potatoes – raw potatoes are toxic to rats and might cause disturbances to gastrointestinal cells.  Three different varieties of potatoes were fed to the three different groups of rats (Royal Society 1999).
  4. Science should be published in peer-reviewed literature and not on TV. Scientists are expected to submit their findings to peer-review and publication in scientific journals.  In their review of the Pusztai claims, the Royal Society concluded that scientists should submit their work to journals (Royal Society 1999).  Peer-review is not always a guarantee that researchers’ conclusions are sound either.  Lancet published the paper by Ewen and Pusztai over the objections of reviewers: (news.bbc.co.uk/1/hi/sci/tech/472192.stm).  Perhaps in some misguided sense of fairness or balance, some journals have published unsound papers that make claims about the safety of GM crops (Shantharum and others 2008).


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

Fedoroff NV, and Brown NM (2004). Chapter 9 Poisoned rats or poisoned wells in Mendel in the Kitchen: A Scientist’s View of Genetically Modified Foods, Joseph Henry Press, Washington, D.C.

Kuiper HA, Noteborn HPJM , and Peijnenburg ACM (1999).Adequacy of methods for testing the safety of genetically modified foods.

Lancet 354 :1315-1316. Lemaux P (2008). Section 3.2.Were potatoes genetically engineered with a lectin protein unsafe to eat? In Review: Genetically engineered plants and foods: a scientist’s analysis of the issues (Part I).

Annual Review Plant Biology 59:771–812. Royal Society UK (1999) Review of data on possible toxicity of GM potatoes. royalsociety.org/Review-of-data-on-possible-toxicity-of-GM-potatoes/PDF file. Accessed Dec 6 2008.

Shantharam S, Sullia SB, and Swamy GS (2008). Peer review contestations in the era of transgenic crops. Current Science 95(2):167-168. Discusses the problems involved in bypassing the peer review system in science and other misuse of scientific evidence as it applies to agricultural biotechnology.

Genetic Roulette Falsely Claims: GM potatoes damaged rats.

  1. Rats were fed potatoes engineered to produce their own insecticide.
  2. These rats developed extensive damage to their digestive tracts and other organs.
  3. Genetic engineering was the cause of the changes observed in the rats.

In 1998 S.W. Ewen and Arpad Pusztai claimed to have conducted experiments revealing variations in the thickness of intestinal linings of rats when they were fed diets containing either GM or non-GM potatoes. The work was published the following year in the British medical journal The Lancet.