Genetically modified corn caused cancer in rats, a study has found.
The French government has ordered an investigation, possibly leading to EU intervention, after the study revealed rats that were fed one of the bestselling strains of genetically modified corn suffered tumours and multiple organ damage.
Scientists said the controversial French study, published today, raised serious questions about the safety of GM foods and the assurances offered by biotech companies and governments.
King's College molecular biologist and GM expert Michael Antoniou said he was shocked by the 'extreme negative health impacts'.
"It shows an extraordinary number of tumours developing earlier and more aggressively - particularly in female animals," Dr Antoniou said.
The research, at France's Caen University, looked at the impact of eating a GM diet over the two-year life of a rat. According to London's Daily Mail, all GM safety assessments to date had been based on rat feeding trials lasting only 90 days.
The corn was genetically modified to withstand spraying with glyphosate, the main chemical in the weedkiller Roundup, developed by Monsanto. The idea is that the corn can be sprayed without being damaged, while weeds are destroyed, the Daily Mail reports.
The tests looked at the impact of several scenarios including eating the Monsanto-produced GM corn (NK603), eating the GM corn sprayed with Roundup, and consuming Roundup at low doses in water.
The study found that between 50-80 per cent of female rats developed large tumours by the beginning of the 24th month, with up to three tumours per animal and up to 70 per cent of females died prematurely compared with only 20 per cent in the control group
Tumours in rats of both sexes fed the GM corn were two to three times larger than in the control group
The study, led by molecular biologist Professor Gilles-Eric Seralini, acritic of GM technology, and published in the US journal Food and Chemical Toxicology, states that the GM corn and Roundup weedkiller 'may cause hormonal disturbances in the same biochemical and physiological pathway'.
But Anthony Trewavas, professor of cell biology at Edinburgh University, questioned the way the research was conducted, saying the number of rats involved in the study - 200 - was too small to draw any meaningful conclusions.
"To be frank, it looks like randomvariation to me in a rodent line likely to develop tumours anyway," he said.
French Agriculture Minister Stephane Le Foll ordered an immediate probe.
"Depending on the investigation, the government will urge the European authorities to take all necessary measures to protect human and animal health," they said.
"(The measures) could go as far as invoking emergency suspension of imports of NK603 corn to Europe pending a re-examination of this product on the basis of enhanced assessment methods."
Green groups say the crops could be dangerous to health and the environment, although this claim has so far found no traction in large-scale studies.
In 2009, the European Food Safety Agency (EFA) panel on GM organisms determined that NK603 was "as safe as conventional maize".