Healthy Skepticism: Genetically Modified Foods

In my recent post on Organic foods I came to the somewhat ambivalent conclusion that, though there is not a lot of evidence to support the idea that there is a huge tangible benefit of an organic diet over a conventional one, it is nonetheless a healthy diet. My only caveat was that we should not mandate the organic methods because those processes lead to a smaller yield on some important crops. One of the biggest arguments made in favor of Organic agricultural methods, however, is that there is potential danger in many of the genetically modified crops that are used for world-wide food distribution.

bigstock-Food-4708340The debates surrounding Organic food and Genetically Modified (GM) foods are often conflated indicating a belief that evidence in support of Organic foods is also evidence against GM foods. It is not. Though these are related issues they are indeed separate; evidence that supports organic health benefits says nothing at all about whether GM crops are harmful.

This is not an easy topic to research because there is evidence to support high-level arguments on both sides of the issue. However, it appears as though opinion on the matter often divides along the same line as the politics of the individuals making the argument. This is terribly unfortunate and can have a very negative effect on public discourse. Science is its own entity and does not adhere to political party lines.

Monsanto logoAn example of political dispute lies in the perception of Monsanto. This is one of the major producers of genetically modified foods and to many on the left it is an example of a purely evil enterprise while many on the right are reflexively defensive of Monsanto and therefore simply dismiss any evidence that may show potential problems with food production or public health.  Whatever side of the argument you are on, vilifying Monsanto is neither a benefit to public education nor to science. Neither is there any benefit in portraying them as saintly. Monsanto is a company like any other company; they have a business model, a product, and they want to make money. While they should most certainly be held accountable if they are negligent in reporting any potentially harmful effects of any of their processes or products, it is unrealistic to assume that they are an inherently evil or an inherently benevolent organization.

Even when the debate doesn’t degrade into partisan arguments it is hard to sift through the wealth of evidence to make sense of the information. In May of 2013 the journal Nature ran a series of articles to help shed some light on the topic. I am going to look at one article by Natasha Gilbert because, while she does seem from the outset to be opposed to GM foods, she approaches the topic with a respectable amount of moderation.

Genetic modifications are made to plants to increase crop output by making them resistant to disease, pests and parasites, and harsh climates among other things. According to many industry advocates, GM foods have increased agricultural production by $98 billion U.S dollars and prevented an estimated 473 million kilograms (that’s over a billion pounds) of pesticides from being sprayed. To this end, it might be safe to assume that advocates on both sides of the argument would find some common ground. However, that is not the case. According to Gilbert there are numerous complexities that have been overlooked by this industry that zealously promotes the above facts despite questionable or inconsistent evidence. Gilbert says that there are three pressing socio-environmental concerns that come to the forefront in the GM foods debate.

Amaranthus_palmeriThe first concern is that GM crops have led to herbicide resistant weeds. There is apparently evidence to support this claim. In the 1990s GM cotton was developed to be resistant to glyphospate (otherwise known as Roundup®), which is the herbicide used to kill Palmer Amaranth, a weed that can be very damaging to cotton crops. Evidently the combination of GM crops and glyphosphate worked very well for a time but then ceased to be effective. According to Gilbert,”The herbicide crop combination worked spectacularly well – until it didn’t. In 2004, herbicide-resistant amaranth was found in one county in Georgia; by 2011, it had spread to 76.” It was estimated that farmers were losing half their crops to weeds.

Now this is certainly a vivid example that will definitely rile someone who doesn’t like GM crops, Round upit even riled me a bit, but it is important to remember that herbicide resistance can happen in non-GM crops as well, and while there may well be better evidence to support this, the above information does not show whether the herbicide resistance occurs as a result of the GM crops transferring their glyphospate resistance to the amaranth or as a result of the weed adapting to repeated exposure to the herbicide, which happens frequently in changing ecosystems. According to Lingefelter and Hartwig (pg 18), depending on the herbicide family and weed species, herbicide resistance can occur within 5 to 20 years. Well within the time-frame described above. Again it may well be that the Palmer Amaranth in the example was altered through cross-contamination. My point is that we can’t tell from the above example.

Gilbert’s second pressing concern is that GM cotton has driven farmers to suicide. This is a rather alarming claim that seems to warrant serious investigation. According to Gilbert, however, it is a rumor that began when Vandana Shiva, an environmental activist, made the claim that “270,000 Indian farmers have committed suicide since Monsanto entered the Indian seed market. It’s a genocide.” This information has indeed been satisfactorily disproven. Research shows that between 1997 and 2007 the number of suicides did rise from 100,000 to 120,000 but that the number of suicides among farmers actually remained somewhat constant at about 20,000 per year (Gruère, G. P., Mehta-Bhatt, P. & Sengupta, D ). These suicide numbers are alarming statistics in their own right but since Monsanto did not begin selling GM seed in India until 2002, five years after the increase began,  it is clearly incorrect to blame them for the problem.

The third pressing concern is that transgenic DNA is spreading to other plants. In 2002 a paper was published in Nature by David Quist claiming that genetic analysis revealed that corn in Oaxaca, Mexico was tainted with DNA that was used to express transgenes that make Monsanto corn insect and glyphospate resistant. Quist and colleagues speculated that this resulted from the local corn having cross bred with GM corn and become tainted. This led to a large media blitz for the people of Oaxaca and led many to blame Monsanto for tainting Oaxacan culture, where corn is considered sacred. The problem was that when other researchers tried to replicate Quist’s results they weren’t able to do so. Further there were many criticisms of the methods used by Quist and his team. Ultimately the editors of Nature, while not retracting the Quist study, did state that “In light of these discussions and the diverse advice received, Nature has concluded that the evidence available is not sufficient to justify the publication of the original paper.”

Based on the above three cases it’s relatively easy to see that the evidence is somewhat nebulous on both sides of the debate making it easy to interpret the information in a way that confirms what we already believe. This is confirmation bias and it is prevalent in all decision making.  In our search to find answers to important questions such as these, none of us has an opinion that is free of bias. The fact that there is contradictory or inconsistent evidence is likely an indication that we aren’t asking the right questions. This phenomenon is not new but in fact has been recognized for over 50 years.

In 1960, P.C. Wason conducted an experiment where he observed how we come up with and then test our own conclusions (Wason, 1960).  In his study, he presented subjects with a triplet of numbers then asked them to figure out the rule that was used to generate the sequence (is the sequence all even numbers, all odd numbers, all consecutive numbers?). The subjects then tested their proposed rules by suggesting additional triplets, after which they were told whether their suggestions were consistent with the actual rule.

What Wason found was that his subjects only looked for number triplets that were consistent with their preconceived rules. For example, if the subjects were given the triplet 2-4-6, they were likely to assume that the numbers were successive even numbers. They would then go on to test whether this hypothesis was true by coming up with several different combinations of successive even numbers. If however, the actual rule were simply that the next number had to be higher than the one before it, these subjects, for their lack of testing any alternatives, would conclude that they were correct, when in fact they weren’t.

So what does an old cognitive psychology experiment have to do with GM foods? Well, the debate about GM foods is carried out by humans and, for better or worse, that means it will always be driven as much by a desire to be correct as it is by the spirit of inquiry. So far people on both sides of the argument seem to have generated hypotheses that are consistent with some of the evidence but as of yet we haven’t found reliable answers. This is likely because the debate only appears to consider whether GM foods are a natural hazard or if that notion is complete nonsense; a false-dichotomy if ever there was one.  Very little consideration appears to be given to the idea that there might be another more accurate conclusion, like the presence of smaller, yet potentially manageable risks associated with GM foods.

Based on the evidence it may prove to be true that GM crops can transfer DNA to non-GM plants of the same species and perhaps even across species leading to herbicide-resistant weeds. This does present potential problems for food growers. If, however, we are able to feed more people because of GM foods, it is a tough argument to make that we shouldn’t move forward.  There is little evidence that shows that eating GM foods is bad or harmful, which means GM will likely continue to advance as an important branch of food science.

To be honest, when I sat down to research this post, I was strongly in favor of GM foods. Frankly, I still am, however I can’t escape the idea that it’s worth giving some thought to the potential problems associated with herbicide resistant weeds because the estimated annual loss of productivity caused by noxious weeds in 64 crops grown in the U.S. is roughly $7.4 billion. That is substantial amount of money that  has the potential to drive up food costs by a significant amount. I wish there were an easier answer to the question of whether we should simply let GM foods move forward unregulated or if we should monitor them with suspicion but there isn’t at this point. We have to continue to weigh the evidence while doing our best to dodge that problem of confirmation bias.


  1. Gruère, G. P., Mehta-Bhatt, P. & Sengupta, D. Bt Cotton and Farmer Suicides in India. Discussion paper 00808 (International Food Policy Research Institute, 2008).
  2. Wason, P.C. On the failure to eliminate hypotheses in a conceptual task. Quarterly Journal of Experimental Psychology, 12, 1960; 129-140. URL

One thought on “Healthy Skepticism: Genetically Modified Foods

  1. Nicely done! It is refreshing to read a blog that doesn’t just slam GM food, but rather, looks at them critically and in a non-biased way.

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