Dr Pusztai describes the results of – and the political fallout from – his landmark 1999 study that found GM insecticidal potatoes had toxic effects on rats

GMWatch has published a series of interviews with the late scientist Dr Arpad Pusztai, conducted in March 2002 by the journalist Andy Rowell, as part of his research for his book, Don't Worry, It's Safe to Eat. Dr Pusztai carried out the first safety research on a GM food plant. Andy kindly gifted this interview archive of recordings to GMWatch and wishes them to be made public.

The archived page of recordings is here.

In these interviews Dr Pusztai describes the results of his landmark 1999 study that found that GM insecticidal potatoes had toxic effects on rats. He also details the political fallout from his public announcement of these findings in a brief 150-second appearance in an episode of the documentary series World in Action. Pusztai said that based on his findings, he would not eat these potatoes and that it was unfair to use our fellow citizens as guinea pigs by putting GM foods into the food supply.

The GM potatoes were engineered to express an insecticidal lectin (type of protein) called GNA, derived from a snowdrop gene. GNA lectin was chosen specifically because Dr Pusztai and his collaborators had, over a period of eight years of research, established that it was non-toxic to mammals in its natural form.

The GM GNA lectin-expressing potatoes were found to cause a proliferative (pre-cancerous growth-inducing) effect on the gut, as described in a peer-reviewed publication in The Lancet.

Another finding was that the GM-fed rats had a reduced brain size – a finding that Pusztai felt was so controversial that he did not publish it. 

Mechanism of toxicity unknown

The mechanism of the GM potatoes' unexpected toxicity is not clear from these experiments. Pusztai was not able to follow up on his research to find out, because after he went public with his findings on British TV, he was fired from his job and barred from access to his lab. His research team was disbanded and a gagging order was imposed on him while his institute, the Rowett, carried out a hostile "audit" of his work. You can read more about these events here in this definitive account by Andy Rowell, extracted from Don't Worry, It's Safe to Eat.

The GM potatoes used in the experiment were destroyed. This was regrettable, as well as anti-scientific. If they'd been put into deep frozen storage, today's molecular analysis techniques could easily have established the source of the toxicity of the GM potatoes – something that now we won't ever know.

However, in the recordings, Pusztai puts forward the hypothesis (for which he states that there was at that time no evidence) that given the toxicological findings related to the gut, which resembled a viral infection, a potential culprit was the cauliflower mosaic virus (CaMV) 35S promoter, engineered into the GM potatoes to drive expression of the transgene. Research shows that the CaMV 35S promoter can drive expression of genes (including transgenes) in mammalian cells – albeit not as strongly as in plants – with unknown effects. But it's equally possible that some other mechanism of toxicity is responsible.

GNA lectins have continued to be genetically engineered into plants to kill insects.

The Bt toxin protein in GM Bt crops is also an insecticidal lectin. GM Bt crops have been found to have harmful effects on laboratory animals.

Lessons on GMO regulation

In the current climate of lobbying for deregulation of a new generation of GMOs, we would do well to bear in mind Dr Pusztai's reply to CSIRO scientist and GMO enthusiast Dr Roger Morton, which we published in 2001. Dr Morton had claimed that GM foods are well tested and that there is a significant body of scientific literature supporting the safety of these foods. That was – and still is – far from the truth, as Arpad knew.

Prophetically, Arpad wrote: "The only thing the GM biotech industry needs to do in future is not do any testing as then the myth of the safety of GM food will be maintained for eternity. I am sure, to judge by present standards, that they are well on their way to achieving this."

Those who are interested in the body of peer-reviewed research showing toxic and allergenic effects of GM foods (including commercialised ones) are recommended to read the book GMO Myths and Truths, in its 4th edition.