So, for my first article, I selected "Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize" published by Seralini, et al, in Food and Chemical Toxicology in 2012. This is one of the few articles I could find in pubmed which referred to health impact of GMO and has been a cornerstone in the anti-GMO movement.
As you can imagine, Monsanto wrote a list of counter-arguments to Seralini's findings. There are a lot of other articles critical of Seralini's paper, and I'll take a look at those later on. At the same time, Seralini recently wrote counter-arguments to Monsanto's counter-arguments, so I'll read that later on, too.
- Seralini et al perform a 2 year detailed rat feeding study (if you disapprove of using animals in scientific studies, you'd better stop reading!).
- The rats were fed the Roundup (R) tolerant NK603 strain of corn, developed by Monsanto. The control mice were fed the closest strain of corn that had the absence of the Bt transgene (for more info on Bt, please see http://en.wikipedia.org/wiki/Bacillus_thuringiensis)
- The R-tolerant (i.e. GM) corn was split into two groups: one was treated with Roundup and one was not. Then they made rat-food with different amounts of the GM corn which was grown with or without Roundup: 11, 22, and 33% corn. An additional variable they looked at was the presence of Roundup in drinking water.
- In total, there were 10 groups of rats. 100 male and 100 female rats were split randomly into the groups.
- Plain water, plain corn
- 11% GM corn without R
- 22% GM corn without R
- 33% GM corn without R
- 11% GM corn with R
- 22% GM corn with R
- 33% GM corn with R
- Plain corn, Dilution 1 of R in water
- Plain corn, Dilution 2 of R in water
- Plain corn, Dilution 3 of R in water
- Blood and urine samples were examined from the rats. When an animal was sacrificed, a whole slew of organs were examined.
- Authors present a plethora of findings (I love that word... Plethora... Always reminds me of the Three Amigos). I'm plagiarizing directly from the paper in a few of the sentences listed below. There are plenty of more findings, but these are the ones that stood out to me:
- More rats died in the groups of rats whose diets had the GM maize.
- Females who were drinking the R-treated water had shorter lifespan
- Females had more frequent tumors than males, the majority of them being mammary tumors.
- Up to 14 months in the study, none of the control rats had tumors while 10-30% of the females had tumors with the exception of the 33% GM + R rats
- Authors provide lots of pictures of rats with giant tumors
- In females, androgen/estrogen balance was modified.
- None of the findings were proportional to the dose of treatment
- Authors note that animals fed NK603 without Roundup (R) application also had enhanced tumor incidence and mortality rate. They hypothesize that this may be due to the imbalance of two metabolites (these are molecules that control metabolic pathways), which they had found to be significantly decreased when compared to controls. (If you aren't sure what was done here, it's basically the same thing that your doctor does at a checkup: blood work and urine analysis. The authors of the paper looked a lot of different variables including things like glucose, cholesterol, hemoglobin, etc, and found two factors that were significantly different from controls).
- Death in males was primarily due to messed up liver and kidney function. Again, they attribute this to the imbalance of the two metabolites.
- The authors found that GM maize fed groups with or without R application had decreased mRNA transcription because the DNA was packed more tightly.
- The authors note that the concentration of Roundup used to treat the rats was way below the limit set by the EPA, yet there were "severe hormonal-dependent mammary, hepatic, and kidney disturbances".
Holy missing statistics, Batman!
Here are my thoughts, but I can summarize this by saying that there's a reason why the paper was published in a journal whose impact factor was 3 (and for all you conspiracy theorists, it wasn't Monsanto paying the publisher to get the article quashed). As a comparison, the New England Journal of Medicine's impact factor is 53.
- Dudes, how could you publish a paper without doing any sort of statistics for your findings?? The only place where statistics were performed were for the biochemical analyses, and I believe that they did stats only because they were fishing for something. They found significance in only two secondary metabolite levels and they blamed all the findings in the paper on these. When reviewing this article, my hubby pointed out that he didn't take stats 101, so I should explain why this is important. Here's my feeble attempt: Statistics basically allow you to determine is something is random or not. God knows how many times I thought that I had discovered something important, but when the numbers were crunched, there was nothing there. For example, I clearly remember a case where I found a DNA mutation in a large number of the patients I was studying, and it was present at a seemingly less frequency in the controls. When a statistical analysis was performed, it was not found to be statistically significant. Meaning that it was random. If I had a completely different group of patients, there was a good likelihood that the mutation would have been present in the same frequency as the controls. That's why stats matter. The control mice DID get tumors. The question that stats have to answer is whether the treated mice got more of them and whether it was sooner.
- Why in the world wouldn't you do more work to explain why there's no link between dose and findings (I hate to call them "findings" since no stats were done)? The authors claim that there's probably a threshold, and that they hit that threshold with the lowest dose. (11% GM) If that's the case, then they should have looked at anything lower than 11% to see if that's true. Also, if your hypothesis is that the tumors are due to imbalances in the metabolites, then you could have even done an in vitro study. They might have even seen the imbalance by feeding the rats just one time, yet they failed to do it. The worst part of the whole thing is that there's no explanation why the most concentrated doses fail to exhibit symptoms. #epicfail
- If their hypothesis is that the imbalance in the metabolites causes tumors in the mice, then they should have looked at the metabolite levels in the rats that developed tumors vs the rats that didn't.
- Ideally, I think they should have more rats. There's only 10 rats of each gender in each group. When the authors make statements like "10-30% of the females had tumors" that means that only 1 rat had a tumor in one of the groups. I think that it's for this reason that the stats weren't presented.
- My final point is just a personal bias: as a geneticist, I would have liked some attempt at explaining why the authors observed different DNA packaging.
I'll review Monsanto's rebuttal next week.