Séralini’s study was the first and only attempt to follow up Monsanto’s study on the same GM maize. Séralini’s team wanted to find out whether the signs of liver and kidney toxicity found in the GM maize-fed rats in Monsanto’s study were of negligible importance, as Monsanto claimed, or developed into serious disease. They found that the signs of toxicity seen in the Monsanto study escalated into serious organ damage.
Séralini designed his study as a direct follow-up to a previous study on the same GM NK603 maize conducted by the developer company, Monsanto.
Monsanto’s 90-day rat feeding study had revealed statistically significant differences in multiple organ function parameters, especially in the liver and kidneys, between the GM and non-GM maize-fed groups.
These differences in the GM maize-fed group could have been interpreted as signs of toxicity and the onset of chronic illness. But the Monsanto authors dismissed the findings as not related to the GM maize and as not “biologically meaningful”. The European Food Safety Authority (EFSA) accepted Monsanto’s interpretation.
Séralini’s study was the first attempt to follow up Monsanto’s study and to find out whether the differences found in the GM maize-fed rats really did not matter, as Monsanto claimed, or developed into serious disease. The study found that the signs of liver and kidney toxicity seen in the Monsanto study escalated into serious organ damage.
Séralini’s study proved that Monsanto’s and EFSA’s view that the changes seen in Monsanto’s study were not biologically meaningful was incorrect. It also showed that 90-day studies are not sufficient to evaluate the long-term health effects of GM foods and threw into question all GMO approvals granted on the basis of such studies.
 Hammond B et al (2004). Results of a 13 week safety assurance study with rats fed grain from glyphosate tolerant corn. Food Chem Toxicol 42(6): 1003-1014.
 European Food Safety Authority (EFSA) (2003). Opinion of the Scientific Panel on Genetically Modified Organisms on a request from the Commission related to the safety of foods and food ingredients derived from herbicide-tolerant genetically modified maize NK603, for which a request for placing on the market was submitted under Article 4 of the Novel Food Regulation (EC) No 258/97 by Monsanto (QUESTION NO EFSA-Q-2003-002): Opinion adopted on 25 November 2003. EFSA Journal 2003(9): 1–14.