Source: Peta Firth, Scientific American, May 1999
British scientist Arpad Pusztai, who was fired last year from the Rowett Research Institute in Aberdeen, Scotland, and banned from speaking to the press for a while, told a parliamentary select committee on March 8 in London he had no regrets about his comments that led to his dismissal. Humans, he had said, were being used as guinea pigs in a vast experiment with genetically modified (GM) foods.
Pusztai’s testimony to the committee followed headlines in British newspapers screaming that a scientist had been gagged and his findings suppressed to keep secret that genetically modified foods threaten health. Conspiracy theories abounded–namely, that President Bill Clinton had personally pressured Prime Minister Tony Blair to give biotechnology companies, including Monsanto, a freer rein in planting GM crops. An admission on March 1 from John Prescott, secretary of state for Environment, Transport and the Regions–that the British government has indeed received representations from its U.S. counterpart about GM crops–did not help.
The furor started last August, when Pusztai released to the media results that he said indicated that rats fed potatoes genetically engineered to contain a lectin from the snowdrop plant–a naturally occurring–had suffered damaged immune systems and stunted growth of vital organs. The results stood in stark contrast to safety claims made by biotech companies and to the received wisdom of the harmlessness of transgenic crops.
Four days after his announcement Pusztai, a renowned scientist who pioneered studies on the effects of lectin, was suspended. The Rowett institute stated he had muddled his findings. Quietly, over the ensuing months, Rowett invited a group of independent scientists to audit Pusztai’s work–and the audit found that his conclusions were indeed erroneous, although it absolved him of the more serious charge of scientific fraud.
Other scientists, though, came to Pusztai’s defense. Two researchers forwarded his data to 21 scientists, who later issued a memorandum in February that said, “We are of the opinion … that the consumption of the GM potatoes by rats led to significant differences in organ weights and depression of lymphocyte responsiveness compared to controls.”
A study that criticized the Rowett audit and confirmed Pusztai’s results also got some backing. Done by pathologist Stanley Ewen of Aberdeen University, a friend of Pusztai’s, the work was examined by Thorkild Bøg-Hansen, a lectin expert from the University of Copenhagen (and one of the researchers who forwarded Pusztai’s results to others). He concluded that “Dr. Ewen’s results clearly showed the errors in the audit report that followed Dr. Pusztai’s suspension from the Rowett Research Institute. The experiments clearly showed that … the GM potatoes caused a major intraepithelial lymphocyte infiltration similar to inflammatory responses.”
Vyvyan Howard, a toxicopathologist at the University of Liverpool and Pusztai supporter, says that the results showed the main risk of GM food to be “long-term, low-dose toxicity from subtle changes to the nature of the food chain.” He describes Pusztai’s findings as unexpected and not totally attributable to the lectin. In other words, the genetic modification process itself was causing unpredictable outcomes. Speculations include virus promoters (mechanisms used to switch on the inserted genes) and possible unintended switching off of beneficial genes. “It is precisely this type of finding which means that animal testing for developmental toxicological effects is essential,” says Howard, who also argues that the “mixture problem” must be addressed as well. “None of us eat only a single food. The effects of mixtures to my knowledge have not been addressed,” he notes, concluding that “human volunteer testing would probably be advisable.”
Tom Sanders of King’s College London, a nutrition expert and a member of the government’s Advisory Committee on Novel Foods and Processes, is not convinced by Pusztai or his supporters. After reviewing Pusztai’s experiments, he maintains that all they definitively proved was that eating raw potatoes, which are indigestible, is harmful to mammals– “something that has been known for many years,” he asserts.
Sanders also says that carrying out full pharmaceutical-style testing on GM foods would be impossible, because low-level poisons ostensibly from GM products would not appear in ordinary toxicological testing. He also points out that testing for human allergenicity with animals is not possible. He suggests instead that known allergens be banned for use in GM food, along with markers used to tell which foods have been modified.
Jim Dunwell of the plant sciences department at the University of Reading has another point against Pusztai: all potatoes are not alike, and toxin levels can vary widely between different tubers before any modification is carried out. “Many assertions that are made against GM crops are not backed up by sound science,” he contends.
Both Sanders and Dunwell note the potential benefits from genetic modification–food engineered to prevent tooth decay or to deliver vaccines. Genetic engineering could cut the need for pesticides. But both also admit its risks. Sanders says that “each crop needs examination on a case-by-case basis. It is dangerous to extrapolate from one to another.” They also admit that genetic engineering could be a threat to the environment, especially if tests are not conducted locally. “The English countryside is not the American prairie,” Sanders comments.
In the next few months, the Royal Society–an independent science academy established in 1660–will complete its own review of Pusztai’s findings and of its own stance on the toxicity and allergenicity of GM foods. Only then might residents of Britain–and the rest of the world–move a step closer toward understanding the health threats, if any. But anyone after a definitive answer will be disappointed–science doesn’t deal in absolutes, and the debate will surely rage on.