January 29, 2010
Monsanto conducted studies to evaluate the toxicity of genetically modified (GM) corn on rats as part of European regulatory registry of GM food and feed, prior to commercialization. To our knowledge, only a summary of the findings were made available to the public (for examples see European Food Safety Authority reports NK603, MON863). Greenpeace sued Monsanto to access the original study data, which it then passed along to French investigator Dr. Joël Spiroux de Vendômois, who published a reanalysis of the Monsanto study.
Unlike what was concluded in the Monsanto study, Vendomois’ group’s reanalysis found consumption of GM corn to be associated with rat kidney and liver toxicity. The strains of GM corn evaluated in the study (NK 603, MON 810 and MON 863) contained residues of chemicals that allow the plants to tolerate herbicides or insecticides, such as Round-up.
Online sources were quick to cite the GM corn article as evidence of the ills of GM crops. At the time of this writing, social bookmarking sites Reddit and Digg had a combined total of 4,341 tags/votes for a single Huffington Post article about GM corn study.
It is useful that the Huffington Post is raising awareness of GM foods debate; what is concerning is that the media coverage of the study appears to muddle the study conclusions.
Dr. Vendômois and colleagues are quick to say their findings are merely “signs of toxicity rather than proofs of toxicity”; no mention of organ failure in rats is made in the article. This is in contrast with the Huffington Post story that uses organ failure in the title, Monsanto’s GMO Corn Linked To Organ Failure, Study Reveals, and the follow-up story, Monsanto GM Corn Causing Organ Failure In Rats Study: Everything You Need To Know, which further exaggerated study findings to imply a causal link between GM corn consumption and organ failure. Link and causation are distinct concepts and are not interchangeable. Overextending the study’s findings is unwarranted, especially given the study authors’ reservation regarding the quality (and quantity) of the Monsanto data. A similar opinion was expressed from another online source.
It is important to note that Dr. Vendômois and colleagues reanalyzed Monsanto’s data. By their own acknowledgment, the data collected to support the Monsanto study is rife with problems stemming from sample size, and study design and duration. Accordingly, these data shortcomings also plague the reanalysis, meaning that it would still be irresponsible to attempt to draw definitive conclusions.
Dr. Marion Nestle wrote a post in her Food Politics Blog on the GM corn rat study, which attracted insightful comments from readers. One commenter on her blog writes:
People have to realize (and scientists should be well aware of this) that statistics are a tool and we are expected to use them honestly. But there is still a large human/subjective component at work, in experimental design, parameter definition, etc., which is just inevitable. We only gain knowledge about the things we measure, but unfortunately cannot gain knowledge about the things we do not measure. This is why our scientific knowledge is dynamic and evolving.
Given limitations of the original dataset, the main conclusion of the paper may be that a better-planned and more thorough study needs to be conducted to adequately characterize potential risks from consuming GM corn.
To add a wrinkle to the argument, this is not the first time the Vendomois group has reanalyzed Monsanto GM corn data. A 2007 reanalysis of a study on GM corn MON863 also showed signs of toxicity in rats. Not surprisingly, the Vendomois reanalysis was criticized by a Monsanto-funded panel of experts published in the peer-reviewed literature.
GM corn is just one of many GM crops in the food system.GAO Genetically Modified Foods Report, May 2002
As academics, scientists, and industry wrestle with the characterization of potential toxicities from GM corn, herein lies an opportunity to remind media sources and the public that single studies, especially those with methodological limitations, rarely provide adequate information to draw confident conclusions or scientific consensus. The peer-review process, publishing in open access journals, transparency in writing and data analyses, and independent validation of study findings are all opportunities to add layers of trust— but all take time. Media organizations that try to overextend results of GM corn cloud the real story, which is that we do not know enough about the health risks and thus should act with caution until a scientific consensus can be reached.
– Dave Love and Keeve Nachman