In April 1998, Arpad Pusztai, a researcher at the Rowett Research Institute in Aberdeen, UK, announced on British television his findings that an unmarketed variety of GE potatoes caused intestinal inflammation in rats. He used the opportunity to decry the hazards of GE foods, exclaiming that it was 'very, very unfair to use our fellow citizens as guinea pigs.' Pusztai failed at first to produce data to back his claim, and was summarily sacked by Rowett. The announcement launched a firestorm of controversy, followed by a series of increasingly heated editorials in the prestigious British medical journal, The Lancet, and ultimately calls by the British Medical Association to ban all GE foods until "proven safe." The Royal Society (the premier British scientific academy) conducted an unorthodox closed-door evaluation of Pusztai's unreleased data and concluded that his study was "flawed in many aspects of design, execution, and analysis and that no conclusions should be drawn from it."

Eventually, Pusztai produced his data for peer review and The Lancet begrudgingly published it, explicitly to avoid accusations of censorship, 18 months after Pusztai's TV appearance. The editors of The Lancet prefaced Pusztai's work with their own comments:

"… it has been peer reviewed by six specialist advisers-- a nutritionist, a human pathologist, a veterinary pathologist, an agricultural geneticist, a plant molecular biologist, and a statistician-- who had several requests for clarification about the design of the study, the laboratory methods used, and the statistical tests applied. Some advised rejection; others encouraged us to go ahead and publish… [One reviewer,] while arguing that the data were 'flawed', also noted that, 'I would like to see [this work] published in the public domain so that fellow scientists can judge for themselves… if the paper is not published, it will be claimed there is a conspiracy to suppress information.'"

Now that the data have come to light, Pusztai's conclusions have baffled many scientists trying to interpret his results-- some have called his findings questionable, confusing, and arbitrary.

On the other hand, however, it is not at all surprising that these particular GE potatoes might be toxic. The potatoes had been engineered to produce a new lectin-- a kind of protein important in many plants' natural defenses-- in order to improve their resistance to insects. Although lectins are very common in plants (including potatoes), researchers have long known that many lectins are especially toxic, antinutrative, and even allergenic (in wheat and peanuts, for example). Additionally, lectins are known to cause the kind of intestinal damage Pusztai later observed in his rats. With this potential in mind, the specific lectin (from the snowdrop plant) genetically-engineered into potatoes was selected because preliminary tests-- tests conducted by Pusztai himself in earlier research-- showed that its impact on rat health would be minimal. Pusztai's feeding study with the GE potatoes was the natural next step in assessing their safety.

The controversy largely stems from Pusztai's claim that the toxic effect of the GE potatoes might not be due entirely to the lectin protein engineered into the potato, but additionally to the process of genetic engineering itself-- a claim that some scientists felt stretched his data too far. Further, Pusztai was criticized for announcing to the media that GE foods were widely "consumed untested" based on his findings that an already-suspect, unmarketed GE variety could pose a health risk.

Will plants genetically-engineered to contain lectin genes adversely affect human health? It seems very possible. But there are none presently on the market, and none for which marketing approval has ever been sought. If the lectin-based strategy should be used in new GE plants, the potential health effects should be very cautiously and thoroughly evaluated before marketing.
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Bateson, P.P.G. 1999. Genetically modified potatoes. Lancet 254:1382.

Editorial. 1999. Health risks of genetically modified foods. Lancet 353:1811.

Ewen, S.W.B., & Pusztai, A. 1999. Health risks of genetically modified foods. Lancet 354:684.

Mitchell, P. & Bradbury, J. 1999. British Medical Association enters the GM-crop affray. Lancet 353:1769.