Review of 10 years of GMO research – they’re safe

Genetically modified organisms (GMOs or GMs) are one of the most well studied areas of biological and agricultural research. However, one of the tactics of the GMO refusers is that “there’s no proof that GMOs are safe.”

Typically, in a debate, the side making the assertion (those that say GMOs are unsafe) are responsible for the evidence that supports their contention. But, the anti-GMO gang relies upon the Argument from Ignorance, trying to force the argument to “if you can’t prove that they’re safe, they must be unsafe.”

Even though arguing with logical fallacies is rarely productive, I did provide an exhaustive list of high-quality peer-reviewed GMO research articles that clearly stated that genetically modified crops are safe. But that’s never enough.

High quality GMO research

In the world of scientific research, the absolute highest quality evidence are meta reviews, which are methods to contrast and combine results from a wide swath of peer-reviewed studies which may be useful in identifying patterns, sources of disagreement and other relationships. Since meta reviews combine the results from a larger number of studies, they can be more statistically significant.

So, if there only was a high quality, peer-reviewed meta review of GMO research findings!

Well, there is one. In a meta-review recently published in a peer-reviewed, high impact factor journal, Critical Review of Biotechnology (pdf), in which the authors collected and evaluated 1,783 research papers, reviews, relevant opinions, and reports published between 2002 and 2012, a comprehensive process that took over 12 months to complete. The review covered all aspects of GM crop safety, from how the crops interact with the environment to how they could potentially affect the humans and animals who consume them.

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The conclusions from this meta review?

The article provided some important results:

  • The scientific literature was heavily in favor of the safety, to both the environment and to humans, of GM based agriculture.
  • Environmental impact studies are predominant in the body of GM research, making up 68% of the 1,783 studies. These studies investigated environmental impact on the crop-level, farm-level and landscape-level. Nicolia and his team found “little to no evidence” that GM crops have a negative environmental impact on their surroundings.
  • Little to no evidence that GM agriculture harms native animal species.
  • Non-GM crops actually tend to reduce biodiversity to a higher degree.
  • Genes of GM crops can spread to wild plants, other crops and microorganisms. However, the authors state that this type of gene transfers occurs naturally all the time with non-GM crops. In fact, local plant genotypes get supplanted by non-GM crops genes. The study also stated that wild plant populations frequently mutate and become resistant to herbicides, so they form their own genetic modification (what we call evolution). Soil bacteria can take genes from all kinds of plants and other microorganisms, but that’s not harmful, it’s part of how evolution proceeds.
  • GMO crops are safe for humans and animals to consume. Before any GM crop can be shipped to a grocery store, they must be shown to be substantially equivalent to non-GM foods. In other words, GM crops should have no toxic biomolecules and have similar (if not more) of the nutrients found in the non-GM foods. This is known as substantial equivalence, and the Italian researchers could not find a single credible paper that demonstrated that GM foods had any detrimental effect on animals or humans that consume them.
  • DNA from GM crops cannot be incorporated into our DNA. This is one of the most ridiculous (and pseudoscientific) claims of the anti-GMO groups. We ingest a lot of DNA every day (from meats to raw plants), and it just doesn’t happen. Most of the DNA is broken down in the digestive tract. And if it were so easy to inject genes into the human genome, then we could really stop spending money trying to figure out how to transfer genes for medical purposes. But what we found out about gene transfer is that it’s so difficult that it may not ever be useful as a medical treatment. What makes anyone think that consuming transgenic DNA (which really is just DNA) will somehow do something that just can’t be done intentionally.
  • In the food and feeding category, the team found no evidence that approved GMOs introduce any unique allergens or toxins into the food supply. All GM crops are tested against a database of all known allergens before commercialization and any crop found containing new allergens is not approved or marketed.


Their overall conclusion:

The scientific research conducted so far has not detected any significant hazards directly connected with the use of genetically engineered crops.

According to an interview with the lead author, Alessandro Nicolia, an applied biologist at the University of Perugia in Italy,

Our goal was to create a single document where interested people of all levels of expertise can get an overview on what has been done by scientists regarding GE crop safety. We tried to give a balanced view informing about what has been debated, the conclusions reached so far, and emerging issues.

This is real evidence, the highest level of scientific evidence. It’s not based on opinion or irrational claims or logical fallacies. This is as close to a scientific consensus as you will find. And once again, even if science were some kind of democracy, and it isn’t, the vote would be 98% in favor of the safety of GMO’s. I

nventing a controversy, where there is none except in the minds of the anti-science crowd, doesn’t help the case of the GMO refusers. Strong, repeatable, and published scientific evidence does. And to date, GMO research clearly supports the scientific consensus behind the safety of GMO crops.

Editor’s note: This article was originally published in October 2013. It has been completely revised and updated to include more comprehensive information, to improve readability and to add current research.

Key citations:

The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!

86 Replies to “Review of 10 years of GMO research – they’re safe”

  1. Pingback: Under the hood |
  2. The problem is that publication bias will mitigate what is available to review in a meta-analysis and he pays the piper picks the tune. A lack of evidence for harm is not equal to proof of no harm. The questions answered by research are determined by what question is asked, and how the research is approached.

    In family medicine we joke when a new drug comes out, use it quickly , before it stops working (and the long term adverse effects come out). We confuse applied science – that which is funded by industry as the shortest route to commercialization, with basic science which asks broader questions with no bias. This latter area used to be funded by government but has practically disappeared.

    The range of harms which might theoretically come from introducing GMOs are so vast and complex that applied science will certainly not answer the important questions. They potentially range from metabolic and genetic health effects for organisms consuming them, where we are introducing new molecules where we cannot track all the potential pathways for, to cross-pollination with wild cousins which exist for ALL domesticated plants (whence they originated), to economic effects on other farmers , to economic effects on crop prices to economic effects of loss of diversity and dependence on fewer sources for seeds both genetic loss and monopolies and multiple other potential complex effects. This is parallel to the idea that we should even consider solving climate change with geo-engineering, again with impossible to predict global consequences. Our narrow view of a clockwork orange predictable world that applied science can solve are frighteningly ignorant. Basic science is about UNCERTAINTY and theory; not certainty which allows us to ignore the precautionary principle when we let genies out of bottles.

    Real scientists understand that there is no more certainty in science than in religion, but applied science easily may be interpreted in the same way as religious dogma. As Voltaire said : "If there wasn't a God, we would need to invent him". Thinking that we can create a Brave New World and solve all problems/eliminate the limits of a finite planet with applied science is an example of the same approach which the human predicament predisposes us to.

  3. Glyphosate has a lower toxicity than table salt. If we stopped using it, we would have to revert back to the older herbicides such as Atrazine which were a lot more toxic and had a far more negative impact on the environment.

    While I will agree that we should continue to strive for safer herbicides, I don't agree that we should reject glyphosate in favour of something much worse.

  4. Skeptical Raptor None – but my statement is about those higher levels of herbicide causing a major worry about GMO crops that people have. Thus the questions abound.. Could just let them all worry, I suppose. Or ask a scientist to carry out a study. Until the evidence is there, the jury is out on this particular aspect of GMO crops.

  5. Skeptical Raptor Did your reading comprehension fail? Did I mention safety? Your effort to change the subject proves the weakness of your position. Did you even look at the paper that you cited?

  6. The onus is upon you to show that they are unsafe. Until such time as you can, your "beliefs" have all the relevance as global warming deniers and creationists. Your anti-science attitude is not appreciated in this discourse. BTW, systematic reviews are not "editorials" but those of us educated in science know that. You sir are just a pseudoscience pusher. You bore us.

  7. Collecting together a bunch of editorials and essays doesn't count as scientific studies. Anyone can go online and find a bunch of opinion pieces on the other side of the argument. Big deal. Just shows the desperation of the anti-science crowd to tout essays from a nursing journal as scientific validation for their claims.

  8. I just want to make a point that this is a small percentage of what we consider "genetically modified" crops. Moreover, and very important, examining the GM crops that are resistant to Roundup is not very useful, unless we're comparing Roundup use in non-GM crops.

    If Roundup is dangerous, and the evidence is not there, then that is not relevant to my discussion of the safety of GM. It is a tiny part of the story, and is more related to the safety of chemicals like glysophate.

  9. I might agree with this. But I don't have a fear of chemicals, given the number of strange chemicals we consume, inhale, or get into the body by whatever means. Sure, I won't drink a gallon of arsenic with my beer (at least I hope not), but human physiology is amazingly resilient in clearing stuff out of the system.

    I guess some people ascribe to the Precautionary Principle, and I do at times, but really we do need evidence.

  10. You must go to the school of "Evolution is just a theory." In science, "significant" has special meaning. It indicates whether a difference is statistically measurable. No, it does not mean that it has detected "some hazards", it means simply that the data appears to be random and the hazards studied show no significant difference than the controls. Please don't invent a bogeyman where one is not described.

  11. "…..has not detected any SIGNIFICANT hazards directly connected with the use of genetically engineered crops."
    which means that it HAS detected SOME hazards. And, given that 10 years it not enough time to study the accumulative effect across several generations of human consumption, scientists cannot with any certainty declare GMO's to be safe.

  12. Mike Muszynski Mike – thanks for your reply. The worry is that 40 ppm is not 'far below any biologically relevant level' but dangerously high. That may not be the case, but that is what is causing all the questions, because there are scientists who claim it's a real problem. So a study would be of great use. I have replied in depth above and covered most of my concerns if you want to look at that.

  13. This is a reply to Mike Muszynski, who has been in conversation with me below. I am posting up here because I feel this is a vital point that all should read. The reason I believe it is important to test food products that have been subject to Roundup herbicide is the worry many people have that there are residues left on crops, corn for example, that cause long-term damage to us. This goes to the heart of the matter. It should be cleared up. I think people's worry should be addressed and there should be some research into such a fundamental concern. In the UK, all food products using GMO crops must be labeled as such by law. Any research into pesticide residues in our food would counter the fears that we have. Frankly, I do not understand why such a simple study has not already been done as it is central to our concerns.

  14. Peter Hobday I've done a cursory query and could not find any published research but I am not a food scientist, I am a plant geneticist. My assumption is that this type of research might not be useful. Which food would one test? To what level of detection? If the EPA allows 40 ppm on "crop residue" and that is far below any biologically relevant level and glyphosate breaks down rapidly under normal conditions and the seed of oil seed crops are what are used (not leaves and stems) and the seeds are processed (under what would be considered harsh conditions) to recover the oil then we would expect far less (if any) detectable glyphosate in foods with processed oilseed ingredients. If it helps, all plants make many pesticidal chemicals themselves, as they do not want to be eaten. And these occur in far higher concentrations than any applied herbicide residue. Caffeine is a natural pesticide but many of us seek out that chemical.

  15. Mike Muszynski In the US, the amount of allowable glyphosate in oilseed crops has been increased from 20 parts to 40 parts per million. The EPA does not test for glyphosphate in foods, so it would be helpful to see some peer reviewed analysis showing how much is left in our food – if anyone has that to hand please. The first genetically modified plant was produced in 1983 – a tobacco plant. In 1994, a transgenic tomato was approved by the FDA for marketing in the US. I don't see any problem with those – much of our agricultural product is genetically engineered for today's markets.

  16. There is actually good research on this. Grocery tomatoes are picked green to survive shipping and then are gassed with ethylene (a natural plant ripening hormone) so they ripen and turn red. But this process short-circuits the normal ripening-on-the-vine process which allows many other chemicals that impart flavor and aroma to develop. So the trade off is, tomatoes are available in stores year round but have little taste vs. tasty tomatoes that won't survive shipping long distances.

  17. Please define "powerful pesticide"? If you are referring to glyphosate (the active chemical in Round Up), this is actually a much safer herbicide than many that are used on non-GMO crops. Glyphosate is broken down rather quickly in the environment and so there would be little to no detectable residue left on the plant material. Moreover, unless you are eating Round Up Ready corn, soybean or cotton leaves, any minute residue would be eliminated through processing. Finally, I am not aware of any commercially available GMO tomatoes on the market today. If they exist, I'd like to know what it is.

  18. We need to see some peer reviewed studies on the safe removal of strong pesticides such as Roundup during food processing. It is a vital question we need to answer. Please publish whatever you have.

  19. That is a logical fallacy called the Argument from Ignorance. It is actually much easier to show that GMO foods cause harm than to prove that they don't (since it's a moving target–"yeah, you showed it was safe for adults, but prove it's safe for 13 year old children who eat a gluten-free diet, are diabetic, and play field hockey"). If GMO food was soooooo dangerous, it should be easy to provide evidence. And to date, no one has, save for some very very bad studies.

    GMO corn has been around for 30 years (and transgenic corn for over 10,000 years). Have we seen an increase in any cancer? Chronic diseases (except for Type 2 diabetes, which is caused by fat, lazy kids, not by GMO corn).

    No, the side making the assertion of danger must show it. Seriously, it's easy to provide the evidence IF there is evidence.

  20. Actually, if you've read some of the peer reviewed articles, you should have less fear. Because of this, they can actually use less pesticides per acre, which is better for the environment.

    But even if that is true, how does this harm you? The pesticides are removed in proper handling of food, and there's less of it to remove than with conventional agriculture.

    And don't go with organic agriculture. You can't feed the planet with it. And scientifically, there is no health benefit for the much higher cost, which makes it worse for the poor.

  21. Thank you for an excellent article and for promoting science! I've been reading your blog now for a few months, so my first comment. I trust the science better than the BS sprouted by anti-GMO folks and their 5 minutes of Google University class knowledge.

  22. Empirical evidence not our only source of knowledge. There is also reason. Just as the best argument against homeopathy is that there is no mechanism by which it could work, there is no mechanism by which GM foods could be unsafe.

  23. I once ordered seeds for a tomato called Long Keeper. True enough, they kept forever, but they tasted vile. They were selected (not directly GM) to be missing an enzyme that makes tomatoes ripen.

    More recently, tomato growers realized they could have those big Jersey tomatoes without the yellow area near the step. Well, they could, but half the flavor was gone.

  24. Susan Belanger Tempelaere If they taste any different it is because you are getting hydroponically grown tomatoes now and don't realize it. Has nothing to do with GMOs and of course heirloom will taste different as they are a different type of tomatoe. Just like different types of oranges taste different.

  25. I don't know enough about the GM debate, so I'm not going to strongly take one side over the other, but your argument that "Typically, in a debate, the side making the assertion (those that say GMO’s are unsafe) are responsible for the evidence that supports their contention" seems that it could easily (and, it would seem, more logically) be reversed. Wouldn't it make more sense to state that the side claiming that GMOs *are* safe would be responsible for the evidence that supports their contention given that GMOs are what is being introduced? In other words, GMOs are the deviation from the norm. It would seem to me that taking the conservative stance that 'if you can't prove they're safe then they *may* be unsafe' is a safer option than the alternative: 'if you can't prove they're unsafe then they must be safe'. Have a think about where that logic got us with smoking and lung cancer…

    Secondly, you state that meta-reviews are the 'absolute highest quality evidence'. This isn't necessarily true. If the review were *systematic* then it would indeed be gold standard. There's no indication in this paper, however, that all available research on GMOs was looked at – in other words, it doesn't sound like this review was necessarily done systematically. Instead, the authors state that they '*selected* original research papers, reviews, relevant opinions and reports addressing all the major issues that emerged in the debate on GE crops'. The operative word in this sentence is *selected*. In other words, unless it is simply that they have been sloppy and failed to state their methodology clearly, it would appear that the authors made judgments on what to include and what not to include in order to represent the major issues. What's more, there is no statement in this review about how this selection process was undertaken – i.e. what were the inclusion and exclusion criteria for papers in this review? – and this is more than just a little troubling. It is also a little concerning that the authors appeared to include 'relevant opinions' as though these are research. A quality systematic review would include only peer-reviewed papers that either analysed original data or reanalysed existing data.

    Thirdly, and I'm not necessarily making any claims of bias in this review, but the authors report no conflicts of interest, yet the lead author, Alessandro Nicolia, acknowledges financial support from ABOCA Spa, a private Italian company that sells plant-based/herbal dietary supplements. It would seem likely to me that this company would have a vested interest in the outcome of such a review. This isn't necessarily a problem, as researchers need to attract funding from somewhere, it just raises a possible source of bias, especially given the apparently non-systematic nature of this review.

    Finally, and this isn't about the review itself but I feel it needs to be said – if you want to sound credible you'd do well to avoid telling people to 'shut up' in the comments section. Bordermine, below, simply raises a valid point about the fact that big business has a strong interest in legislation that would allow GMOs (partly because they can then legally 'own' the organisms produced), and that these companies have a lot of power (because they have a lot of money) to influence debate at many levels. A true sceptic, rather than taking one side over the other and then looking for evidence to support your stance (i.e. confirmation bias), would listen to opposing views when they are voiced.

  26. Irrelevant comments. Your Appeal to Monsanto logical fallacy has no place here.

    Do you have a single peer-reviewed paper in a high impact journal that shows that GMO's are dangerous? Any? No? Then shut up.

    Skeptical doesn't mean what you think it means. It does not mean you challenge the consensus because YOU believe, and belief means no evidence, that GMO's are bad. That's not skepticism, that's just plain ignorance. A true skeptic exams all the evidence, places higher value on better evidence and low value on logical fallacies (for which you seem quite enamored) before accepting or rejecting something.

    Who cares how people vote? I'm a liberal Californian and I knew that prop 37 was crap, shoved down the throats of Californians by Mercola and his gang of lying anti-science bullshit artists.

    See how conspiracy theories work? They can go against you, if you can't use real science.

    So bring me real science. Or really, go kiss the ass of your hippy friends who hang out with the global warming deniers of the corporate elite.

    I'm really good at this conspiracy bullshit. 🙂

  27. I find is curious that there is no article addressing the "Monsanto Protection Act" (HR 933 Section 735). Why does Monsanto need special protection from liability claims if everything is so safe? Reading the details about that Section I find references to GMOs "previously approved for deregulatory status" by the FDA–but the relevant decision-maker at the FDA is Michael Taylor, formerly employed by Monsanto. This is not a confidence-builder.

    I'm in California where we were just subjected to a massive advertising campaign against a simple labeling law for GMOs. This included a Stanford professor insisting that GMO technology is the same as grafting onto rootstocks between closely related species. I may only have a few ag tech classes at my local community colllege but even I know this is BS. You can't graft just any plant onto any old rootstock and you can't cross-breed by conventional means and duplicate the genetic manipulations used to produce the GMOs. The strident and nearly hysterical tone of the anti-Prop 37 ads had the opposite effect on me though they apparently worked on enough people to turn the election. But then in the land of black box voting I'm not sure if how anyone votes matters anyway. BTW take a look at and see if you're "skeptical' about THAT technology.

  28. Hi Mary Ellen, alot of the science that has gone into making fruit and veg hardier for transport etc is due to traditional plant breeding, so cross pollinating different varieties of carrot, tomato or whatever. The lack of tast would also be due to them being picked prior to being ripe in order that they can be transported. If you have the space try growing your own.

  29. To the best of my knowledge, tomatoes found in grocery stores are often picked before they've completely ripened and allowed to ripen as they're shipped. This affects taste. I found that tomatoes and other produce items that were picked when fully ripened tasted much better regardless of breed.

    This is why I will only purchase certain fruits when they are in season around where I live. They just taste better.

  30. Mary Ellen. I think taste is subjective. And it belies the more important issue of shipping food from the source, several thousand kilometers to the consumer. Interestingly, canned tomatoes used for sauces are picked nearer to full ripeness, and probably "taste" better.

    But, taste probably is not an indicator of healthiness or not. It's just a transportation issue.

  31. Mary Ellen Acosta yes, many people including me agree with you, today tomatoes taste phony even cardboard like. I Hear it all the time. Nothing like those grown from Heirloom seeds.

  32. OR, it could be that selecting for hardier skin on fruits and veggies and quicker growth cycles may actually have changed the taste of the fruit/vegetable. If you were around long enough to have had a really good tomato, you would know what i am talking about. (or maybe where you are you can get locally grown organic). Thanks for the information, but i am not even 50 yet, so your theory does not apply to me.

  33. If you think certain things don't taste the same anymore, it could possibly be attributed to your senescence. Age-related changes to taste and smell is a common occurrence.

  34. I am in the group who is wondering about GMO's and their effect on us in the future. I do not read the psuedoscience or the science on the issue, so i appreciate this information you share. I do have a question that is really a complaint. Is the science of engineering better fruit and vegetables- that is, to make them more hardy for transport and more colorful so consumers will buy them, the same engineering that is making vegetables less palatable? Tomatoes do not taste good anymore. Apples have lost their deeply sweet and rich tones of flavor. There are more examples. Maybe i am romanticising how good things were when i was young, but jeesh, i cannot pick up a red tomato and bite into it anymore. It just tastes bland. Just my two cents.

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