ARS researchers have introduced green fluorescent protein into corn lines as a marker for different tissues, which will make it easier to study nitrogen use and grain development and improve corn processing. Here the light kernels are expressing the fluorescent protein in the endosperm layer. Image: Photo courtesy of Adrienne Moran Lauter, ARS.
By Declan Butler of Nature magazine
Europe has never been particularly fond of genetically modified (GM) foods, but a startling research paper published last week looks set to harden public and political opposition even further, despite a torrent of skepticism from scientists about the work.
The study, published in the peer-reviewed journal Food and Chemical Toxicology, looked for adverse health effects in rats fed NK603 maize (corn), developed by biotech company Monsanto to resist the herbicide glyphosate and approved for animal and human consumption in the European Union, United States and other countries. It reported that the rats developed higher levels of cancers, had larger cancerous tumors and died earlier than controls. The researchers have not conclusively identified a mechanism for the effect.
The rats were monitored for two years (almost their whole lifespan), making this the first long-term study of maize containing these specific genes. About a dozen long-term studies of different GM crops have failed to find such stark health effects. An earlier test of NK603 maize in rats in a 90-day feeding trial — the current regulatory norm — sponsored by Monsanto showed no adverse effects.
The explosion of media coverage about the findings has energized opponents of GM food, especially in Europe. French Prime Minister Jean-Marc Ayrault said that, if the results are confirmed, the government will press for a Europe-wide ban on the maize. The European Commission has instructed the independent European Food Safety Agency (EFSA) in Parma, Italy, to assess the study.
Many scientists, however, have already questioned the study’s methodology and findings. They assert that the data presented in the paper do not readily allow the claims to be independently assessed, and they question the study’s experimental design and its statistical analysis of any differences between the treated groups and controls. Other scientists point out that the Sprague-Dawley strain of rats used in the experiments has been shown to be susceptible to developing tumors spontaneously, particularly as they grow older, making it difficult to interpret the results. Monsanto itself said that the study “does not meet minimum acceptable standards for this type of scientific research”.
The €3.2-million (US$4.1-million) study was led by Gilles-Eric Séralini, a molecular biologist at the University of Caen, France, in collaboration with the Paris-based Committee for Research and Independent Information on Genetic Engineering (CRIIGEN), whose scientific board he heads. CRIIGEN bills itself as an “independent non-profit organization of scientific counter-expertise to study GMOs, pesticides and impacts of pollutants on health and environment, and to develop non polluting alternatives”. The article’s publication coincides with the launch this week of a book by Séralini, Tous Cobayes? (All of Us Guinea-Pigs Now?), which tells the story of the research project and is accompanied by a film and a television documentary.
In a written response to Nature’s questions, Séralini and Joël Spiroux de Vendômois, president of CRIIGEN and a co-author of the paper, say that they have been surprised by the “violence” and immediacy of scientists’ criticisms. They argue that most of the critics are not toxicologists, and suggest that some may have competing interests, including working to develop transgenic crops. They also point out some errors by critics, such as claims that graphs in the paper showing rat survival over time do not include data for the controls.