A different spin on the usual Foodie Friday post, today I wanted to summarize the fallout of a recent study in the journal of Food and Chemical Toxicology titled Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. The study claims to be the first long-term (two years) study into the health impact of a genetically modified (GM) tolerant maize crop, and the herbicide Roundup in Sprague-Dawley rats. Before I get into the results, just some quick background information of GM maize, Roundup, and Sprague-Dawley rats. GM maize is corn which has been genetically modified to withstand spraying with glyphosate, the active ingredient in Roundup, and is said to be a Roundup Ready crop. The goal of Roundup Ready crops is to allow the crop to be sprayed without being damaged, while surrounding weeds are destroyed. Roundup, or more specifically glyphosate, is one of the most commonly used herbicides in the agricultural and cosmetic-use industries. Sprague-Dawley rats are commonly used organisms in laboratory studies partly because of its calm demeanor and ease of handling. The average life-span of a Sprague-Dawley rat can range between 193-1100 days, during which time up to 57% of females can expect to develop tumors on a normal diet, and up to 80% of those on a fat-rich diet can expect to develop mammary tumors. This strain of rat is particularly prone to developing tumors, particularly when fed an unrestricted diet.
Back to the paper, the authors chose a 2 year duration for the study, as they were interested in the chronic effects of this diet and noted that “no regulatory authority requests mandatory chronic animal feeding studies to be performed for edible GM crops“, and that currently, approval is based on a 90-day feeding trial. They carried out their study on 10 groups, each group containing 10 male and 10 female rats. 3 groups were exposed to Roundup Ready corn (NK603) with three different proportions (11, 22, and 33%) of the corn incorporated into their diet. 3 groups were exposed to Roundup Ready corn which had been sprayed with Roundup in the field, with the same proportions in the diet as with the Roundup Ready corn alone. 3 groups were exposed to Roundup alone via their drinking water at three different concentrations of glyphosate; 50 ng/L (1.1×10-8% Roundup), 400 mg/kg (0.09% Roundup), and 2.25 g/L (0.5% Roundup) [note: the discrepancy between units is from the original paper]. This leaves only 1 control group (10 males and 10 females), which received a diet made up of 33% non-GM corn and plain drinking water. The authors took blood and urine samples and performed histological analysis of the rats’ principal organs at the end of the trial.
The authors found that in all treated groups, there were 2 – 3 times more deaths amongst the females compared to the controls by the end of the experiment. Females developed fatal mammary tumors and pituitary disorders, and males suffered liver damage, developed kidney and skin tumors and problems with their digestive system. The majority of tumors were only detected from 18 months onwards. The largest tumors were five times more frequent in females than in males and 93% were mammary tumors.These results were highlighted by very graphic photos.
The authors conclude that the biochemical disturbances and physiological failures in the rats are the result of Roundup Ready Corn and Roundup alone. The conclusions of this paper got picked up by a lot of media outlets, where it was quickly reported that Major study proves cancer dangers of GM food, or that GM corn linked to early death in new study, or as the Daily Mail put it, Cancer row over GM foods as study says it did THIS to rats…and can cause organ damage and early death in humans.
However, it didn’t take long for other scientists to speak up about the results (the following links do a much better job than I could at describing the failings of the article, so click through for the full story). The Science Media Centre collected the opinions of many scientists regarding the findings and interpretation of the paper. NewScientist does a great job of clearly summing up the problems with the paper, in a very concise and easy to follow manner, with helpful supporting links. SciCurious gives a great technical takedown of the study at The Crux. Forbes contributor Tim Worstall calls the study rubbish, noting that every research animal in the US has been eating GM food for well over a decade, all without a catastrophic collapse of the population. One of the most scathing and insightful reviews (read: takedown) of the paper comes from Michael Grayer, who blows a gasket while describing the many failings and shortcomings of the paper, which are quickly summarized as very small sample size in the control group (10 animals), many different experimental groups, opaque and non-declared statistical methods, emotionally distressing/manipulative photos of rats, and a fairly apparent conflict of interest that goes undeclared by the lead author.
The conflict of interest of the lead author is a bit troubling as the issue of GM crops is very political, and becoming less about science. Forbes has a great article, Monsanto’s GM Corn and Cancer in Rats: Real Scientists Deeply Unimpressed. Politics, Not Science Perhaps? which highlights the political back story and interests behind this paper, its authors, and funding group. The timing of this paper, and the heated discussion surrounding it, coincides with California Proposition 37, Mandatory Labeling of Genetically Engineered Food initiative which will be on the November 6th ballot. Prop 37 would require all genetically engineered foods in California to be labeled. Gary Ruskin, campaign manager of the Yes on Proposition 37 effort, is using the study to “underscore the importance of giving California families the right to know whether our food is genetically engineered and to decide for ourselves whether we want to gamble with our health by eating GMO foods.” The findings of the study have also found their way into the promotional material for Yes on Prop 37, which will no doubt serve to muddy up the debate.
Aside from getting people talking about GM crops, this paper is also serving a greater purpose. Understanding Uncertainty gives an excellent breakdown of the flawed statistics used in the paper, but it is able to find a silver lining, noting that it provides a fine case study for teaching a statistics class about poor design, analysis and reporting. This paper and the ensuing reaction is another great example of the need for critical reading, and reporting, of scientific articles.
Update: November 28th 2013
Looks like the paper mentioned above is going to be retracted, which is great news, but I somehow doubt the retraction will get as much press or feature on The Dr. Oz Show, as the original publication did.
Update: June 26th 2014
Looks like the paper mentioned above has been re-published, with very little changes and without peer review, in a different journal. Once again the scientific community is criticizing their results and ethics of the authors. The Genetic Literacy Project has complied an excellent list of reactions to this new development.
- GM Corn-Tumor Link Based on Poor Science (news.discovery.com)
- NaturalNews – Mike Adams – Shocking Findings In New GMO Study : Rats Fed Lifetime Of GM Corn Grow Horrifying Tumors, 70% Of Females Die Early – 19 September 2012 (lucas2012infos.wordpress.com)
- William Malaurie – Yes, GMOs are poisonous! (prn.fm)
- Did GM food cause GIANT TUMOURS IN RATS? (go.theregister.com)
- Monsanto’s Roundup And Roundup-Resistant Corn Found To Be Toxic In Rats (businessinsider.com)
- France Orders Probe after Rat Study Links GM Corn, Cancer (happolatismiscellany.wordpress.com)
- Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize (gmoawareness.org)
- Experts Discuss the Findings of the Roundup/GM Cancer Trial (mountainrepublic.net)
- Study prompts calls to ban GE corn (stuff.co.nz)