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Posted by on Oct 8, 2012 in Biology, Genetics, Science, Skepticism | 12 comments

My Take on the GMO Causes Cancer Study

I have fallen into the genetically modified organism ‘discussion’ by accident.  I have a friend who is violently anti-GMO.  This friend regularly posts the lies and fake ‘studies’ that populate the anti-GMO movement.  I started by just looking up a few stats and now, I’m into full-blown deep research mode on this stuff.

The research, really is quite interesting and I may go into more of it.  But the one thing I wanted to bring up here is the concept of cherry-picking.  Why, I keep asking my friend, do you keep bringing up non-peer reviewed studies and ignore the peer-reviewed studies that I present to you?  The ready answer is this massive global conspiracy between Monsanto and the bought government.

Honestly, I don’t like Monsanto and their practices.  I’m not a huge fan of Roundup Ready plants, because that does tend to increase the use of herbicides.  But that doesn’t mean that ALL GM food must be eliminated.

So, finally, a study appears that seems to support the Anti-GM crowd’s claims.  GM food causes cancer.  Well, I was skeptical.  Even though this paper was published in a peer-reviewed journal, it was pre-published alongside 3 articles that all concluded that GM food was not harmful.

I contacted the lead author and got a copy of the paper, which is now available here.

Honestly, after reading the abstract, I could see that this might be a good paper.  After reviewing the graphs (here), I had some concerns.  After reading the paper I have some major concerns.

First, I want to talk a bit about the authors.  This isn’t an ad hominem attack.  If you are talking to a car salesman about which car is best and he describes the virtues of a particular car, oh and by the way I have one for sale here… perhaps you should consider the source.

Now, the lead author, Gilles-Eric Séralini, is also the author of a couple of books.  One of which is title “Genetically Incorrect” and another is “We Can Clean Up”.  These are books talking about how genetic manipulation of organisms is wrong (ironic considering the lab rats he used for this research, but more on that in a bit) and are part of the organic food revolution in France.  Do you honestly think he’s unbiased?

One other point.  Séralini has been censured before for incorrect analysis of data and incorrect procedures.

Another author, Joël Spiroux de Vendômois, is a homeopath.  I’m sorry, but the fundamental principles of homeopathy (like cure like, dilution, rejection of the germ theory of disease) are all wrong.  I’ve talked briefly about this before and I’ll happily go into it again if anyone wants me to.  But the principles of homeopathy aren’t even wrong, they are impossible.

So, there’s two of the authors of this paper.  One seems to be committed to defeating genetic manipulation of organisms and the other (despite being a doctor) doesn’t believe that science works.  Now, would you buy a car from these two salesmen?

Again, this isn’t an ad hominem attack.  These people freely admit that they think these things, but they don’t state so in their paper under  the “conflict of interests” section.  That’s not to say that these people can’t do good science.  We should examine the science… so let’s do that.

Here’s the results graph


Fig. 1. Mortality of rats fed GMO treated or not with Roundup, and effects of Roundup alone. Rats were fed with NK603 GM maize (with or without application of Roundup) at three different doses (11, 22, 33% in their diet: thin, medium and bold lines, respectively) compared to the substantially equivalent closest isogenic non-GM maize (control, dotted line). Roundup was administrated in drinking water at 3 increasing doses, same symbols (environmental (A), MRL in agricultural GMOs (B) and half of minimal agricultural levels (C), see Section 2). Lifespan during the experiment for the control group is represented by the vertical bar ± SEM (grey area). In bar histograms, the causes of mortality before the grey area are detailed in comparison to the controls (0). In black are represented the necessary euthanasia because of suffering in accordance with ethical rules (tumors over 25% body weight, more than 25% weight loss, hemorrhagic bleeding, etc.); and in hatched areas, spontaneous mortality.

They are reporting in the graphic on page 4 that 10 males of the group that was fed Roundup sprayed GM maize died.  Ten animals.  That sounds bad.  Then we learn that there were only 10 animals in that group.  Holy crap, that’s a 100% death rate for those animals.

Now look at the control group.  All animals were fed non-GM maize with no pesticides.  Seven out of 10 died.  Holy crap!  That’s a 70% death rate.

Wait… what?

First let’s look at the actual groups of animals in this study.

  • 10 male rats fed normal diet
  • 10 male rats fed 11% GM Maize, not sprayed with round-up
  • 10 male rats fed 22% GM Maize, not sprayed with round-up
  • 10 male rats fed 33% GM Maize, not sprayed with round-up
  • 10 male rats fed 11% GM Maize, sprayed with round-up
  • 10 male rats fed 22% GM Maize, sprayed with round-up
  • 10 male rats fed 33% GM Maize, sprayed with round-up
  • 10 male rats fed normal diet, but their water had environmental levels of round-up in the water
  • 10 male rats fed normal diet, but their water had half agricultural levels of round-up in the water
  • 10 male rats fed normal diet, but their water had agricultural levels of round-up in the water

The females had similar groupings.  So, there were 100 male rats and 100 female rats divided into 10 groupings.  Then the control group of 10 was compared to each experimental group of 10.

That’s a major flaw in the study.  Most people won’t recognize it because it’s very subtle, but there is a huge statistical problem here.  The potential for cherry-picking is super strong here.  That’s not to say it happened, but then, the complete results of every animal are not published here.

There are simply too many variables.  A proper study would have been 50 male rats as a single test group and 50 male rats as a control group.  The test should also be done using a couple of different breeds (again, more on why that’s a concern in a minute).  I have since learned that 50 animals is the standard for long-tern studies.

Let’s talk for a minute about correlation and causation.

Correlation is the concept that two variables are moving at the same time.  Causation is the concept that one of the variables is moving because of the other one.  An example will serve.  We note that over the last 100 years, the global temperature of the Earth has increased.  We also note that over the same time period, that the number of pirates decreased.  Those two numbers are correlated.  Does anyone think that the lack of pirates is causing global warming (causation)?
Yeah, I didn’t think so.

Scientists use statistical measures to analyze data and determine if two variables are correlated.  There’s no (that is zero) statistical analysis in this paper.  Saying that 70% of a group died is not a statistical analysis.  In fact, one statistician is going to us this paper as an example of how NOT to do studies like this.

Now, let’s look at the causation.  Did the GM, non-sprayed maize group have tumors and death?  Did the GM, sprayed maize group have tumors and death?  Did the normal feed, drinking water with pesticide group have  tumors and death?

The answer is yes to every single one of those.  But note that I left one group out.  The control.

Did the control group have tumors and death.

That’s also a yes.  In fact, if you look at the charts, out of 6 comparisons with the control group, two of the control groups had more tumors and death than the experimental groups.

So we have to ask, what exactly is causing the tumors and deaths in the control group?  Since the paper doesn’t say, we don’t know.  Since we don’t know what is causing the issue in the control group, we cannot say that the same issue isn’t causing the cancer and death in the experimental groups.

That’s the point of a well crafted scientific experiment, to eliminate all but one variable that is then manipulated by the researchers to observe the changes that happen.  This is not a well crafted experiment.  We can’t say that the GM food causes cancer until we can show that the cause of cancer in the control animals does not also cause cancer in the experimental animals.  I’ll talk more about the animals in a moment and, I think, all will become clear.

Statistically speaking, it’s impossible to say that there’s even any correlation between the tested chemicals and crops and the tumors and deaths.  Why do I say that?  Because in every single category, the rats fed the most amount of GM Maize, sprayed GM maize, and pesticide laden water had a higher survival rate than the other two test groups.

This is extremely significant.  It means that something weird is going on.  The authors ‘conclusions’ about a threshold amount of pesticide or mitigating affects of the pesticide on the chemical pathways don’t hold up under this weird condition that the fewest deaths in three case and second fewest deaths in three cases were in the rats fed the most chemicals.

That’s roughly equivalent of saying that you have a better chance of survival if you get shot twice instead of shot once.

Now, I promised a comment on the rats.  The strain used in this experiment were all genetically engineered (by selection)* to be lab rats. These are highly inbred animals.  The particular strain used in this test were virgin albino Sprague-Dawley rats at 5 weeks of age.

Here’s a very interesting report on the fact that 81% of Sprague-Dawley rats end up with multiple tumors after two years (which is the length of time of the study).  So, the study’s authors have used a strain of rats specifically designed to develop tumors and then they are shocked when the rats develop tumors.

This leads me to another point.  In another paper I referred to, my friend pointed out that the same strain of rats was used.  My response was, so what?  In the other paper, the authors were testing for the presence of GM DNA in the rats’ blood and organs, not whether they were getting cancer or not.

Finally, a comment on the nature of the methods.  One method routinely employed in science is called the ‘blind’ or ‘double blind’ study.  These two processes are used to ensure that there is no bias in experiments.  To do a blind study, the person actually making the measurements is not told whether the subject is in the experimental group or in the control group.  Why? Because of personal bias.

If one is not told which group is test and which group is experiment, then bias, even unconscious bias is impossible.  In this case, a researcher might decide that one tumor is different because it’s in a test animal (especially considering the background of the lead researcher).

Now, to my conclusion.

Does this paper show that round-up and GM Maize are toxic?

Do the points in this blog article mean that round-up and GM maize are safe?

What it means is the state of round-up and GM maize is not changed by this poor study and we need to stick with previous studies that used the proper methodology and the proper analysis.

This could have been a very valuable, useful study.  But it just isn’t.


* Keep in mind that maize is a genetically engineered product to (via artificial selection), it doesn’t exist in the wild.

  • Avant Garde

    Séralini’s dishonesty is appalling!!

  • Beth Erickson

    Excellent analysis. Nutrition is a subject in which I’m avidly interested and you did a fabulous job deconstructing this study. Although it’s a hot topic, I have yet to find scientific evidence that GMOs are harmful. Thanks for your work on this. You saved me a lot of time. — Beth :)

    • Smilodon’s Retreat

      Thanks. Unfortunately, those who did not arrive at their conclusion by evidence cannot be swayed by evidence.

      I too haven’t seen much in the way of studies that show GMOs are dangerous. I have seen reports (not peer-reviewed) that roundup ready plants tend to increase the use of herbicides. But dangers from the actual organisms, nope.

      In my opinion, the potential benefits are greater than the potential problems. Feeding 14 billion people by 2050 is the big one. Making sure that 9 million children a year don’t die of malnutrition is another. And making food plants that can grow where nothing grows now would be useful too.

      Honestly, if the population keeps growing, then the only place that has enough space to farm will be… space.

  • Copyleft

    I admit that it’s a less intellectually-rigorous shortcut, but for me, the statement “one of the authors is a homeopath” was all I needed to conclude that the article was bogus or at least highly suspect.

    Homeopathic practitioners are not, and cannot be, scientists.

    • Smilodon’s Retreat

      I agree. But the science must be critically examined, in disgusting detail.

      I maintain that if Hitler (I just Godwined myself) had come up with evolutionary theory, it would be just as valid as Darwin (or Wallace) coming up with it. I doubt that Hitler would have bothered to come up with it and because of human reactions, we would have waited until someone else came up with the same idea.

      You remind me, I need to do a post on homeopathy too.

      • Copyleft

        True, and I’ve used that same argument myself. “If Hitler’s medical experiments had mapped the human genome, the information would still be true and useful.”

        • Avant Garde

          I like this example! I usually say that Bayer being a multinational doesn’t mean that aspirins stop working!

  • Gavin Hubbard

    I’ve been travelling a lot lately; heard the furore over the paper just as I started, and have only now had a chance to start reading it and digging about in others thoughts.

    This is a great – and clear – deconstruction of the paper, and I shall have a proper read of it ( the paper) now too.


  • Beatriz Xoconostle

    Excellent explanation. I wrote myself a comment in Spanish, but sadly, the anti-science movement is pretty strong here in Mexico. We still have a long way to go!

    • Smilodon’s Retreat

      Thank you.

      Just out of curiosity, can you tell me about the anti-science movement in Mexico? I have some relatives (by marriage) from Mexico, so I’m curious. Is it partially based on the Catholic culture?

  • Mike Lewinski

    This is a good analysis and I want to focus my comments on the second and third paragraphs.

    “The ready answer is this massive global conspiracy between Monsanto and the bought government.”

    With people like Michael Taylor in and out of the same government agency that regulates the private sector he’s otherwise employed in, it’s easy to believe there is a conspiracy. There’s a counter-argument to effect: “we need competent people who understand the industry and the science to regulate it”.

    I suspect there’s both factors at work – some collusion and greasing of wheels as well as a general attitude in Washington that people in the industry really do have the expertise to know what’s really going on and are more qualified than outsiders. If it’s good for business it creates jobs, it must be good for the country, right?

    “I’m not a huge fan of Roundup Ready plants, because that does tend to increase the use of herbicides. But that doesn’t mean that ALL GM food must be eliminated.”

    There’s another force at work in the minds of many opponents of GMO agriculture. It’s that there is great hubris in believing humans can engineer nature better than nature intended. Even if a food is really and truly found safe because it is, it’s still rejected and judged as disgusting because it violates a moral sense of the purity (violating the natural order) and possibly also the “respect for authority” moral value (it questions nature’s wisdom).

    I don’t necessarily believe these are conscious thoughts, but I have heard “hubris” a lot in discussions and it points the way to the underlying sentiment.

    There’s an argument by Jonathan Haidt that these moral judgments are more akin to our other feelings. They arise not from the conscious reflective part of the mind, but from the older pre-verbal parts that manage our other emotions. Then we create post-hoc explanations for why we have the morals we do.

    So I don’t think any amount of arguing with some opponents can advance without getting to the real underlying moral problem. Those violated values serve as the filter for cherry picking the evidence. Of course the primary moral violation is the “avoidance of harm” moral, and I think it serves as a buffer for the purity and authority morals.

    • SmilodonsRetreat

      I can agree with all that.

      I will say that I’ve found well over 120 peer-reviewed research papers that are independent (i.e. they list the funding for the research and it’s not corporate) and they all support GM foods as safe too.

      I’ve heard that ‘hubris’ argument as well. And honestly, humans can do things like that better than nature… in fact we’ve been doing it ever since the discovery of fire. We build buildings that are better suited for living in than caves. Of course, our buildings harm the natural environment. We manufacture clothes because nature didn’t provide us with sufficient protection from the environment. Farms are the same thing. Instead of just ‘finding’ food, we plant it, nurture it and then eat it.

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