Séralini and his colleagues had previously found evidence for toxicity of GM feed in data from Monsanto’s own experiments, which they had obtained through a Freedom of Information demand . Monsanto challenged their conclusions and, to no one’s great surprise the European Food Standards Agency (EFSA) supported Monsanto . So the team decided to run their own experiment, using an unusually large number of animals and over a period of about two years, roughly the life expectancy of the rats, rather than the usual 90 days required in toxicity trials including Monsanto’s.
What Séralini and his colleagues found was that NK603 and Roundup are not only both toxic as expected, but also carcinogenic, which was unexpected. The proportion of treated rats that died during the experiments was much greater than the controls; moreover, in almost all groups a higher proportion developed tumours, and the tumours appeared earlier.