toxicity graphic edit

by Megan L. Norris

Summary: As the prevalence of genetically modified organisms (GMOs) continues to rise, there has been an increasing public interest for information concerning the safety of these products. Concerns generally focus on how the GMO may affect the environment or how it may affect the consumer. One specific concern is the possibility for GMOs to negatively affect human health. This could result from differences in nutritional content, allergic response, or undesired side effects such as toxicity, organ damage, or gene transfer. To address these concerns, there have been over 100 research studies comparing the effects of traditional food to genetically modified food, the results of which have been reviewed in various journals [1], [2]. How these results affect regulation can be found through The Center for Environmental Risk Assessment, which hosts a GM Crop Database that can be searched by the public to find GMO crop history, style of modification, and regulation across the world [3]. Though knowing who to trust and what to believe regarding this topic is an ongoing battle, major health groups, including the American Medical Association and World Health Organization, have concluded from the research of independent groups worldwide that genetically modified foods are safe for consumers [4]. Regarding toxicity, this includes any dangers related to organ health, mutations, pregnancy and offspring, and potential for transfer of genes to the consumer.

GMO toxicity: fears and scientific analysis

After genetically modified foods were introduced in the United States a few decades ago, people independently reported toxic effects caused by GMOs. One example is an anti-GMO advocacy group called the Institute for Responsible Technology (IRT), which reported that rats fed a diet containing a GMO potato had virtually every organ system adversely affected after just ten days of feeding [5]. The IRT stated that the toxicity was the result of genetic modification techniques and not a specific case for that particular potato. They claimed the process of making the GMO caused it to be toxic and thus all GMOs were high risk for toxicity.

Scientists across the U.S. and the rest of the world have sought to rigorously test the assertions of the IRT and others to uncover any possible toxicity caused by GMOs. To this end, many different types of modifications in various crops have been tested, and the studies have found no evidence that GMOs cause organ toxicity or other adverse health effects. An example of this research is a study carried out on a type of GMO potato that was genetically modified to contain the bar gene. The product of the bar gene is an enzyme that can detoxify herbicides and thus protects the potato from herbicidal treatment.

In order to see if this GMO potato would have adverse effects on consumer health like those claimed by the IRT, a group of scientists at the National Institute of Toxicological Research in Seoul, Korea fed rats diets containing either GMO potato or non-GMO potato [6]. For each diet, they tracked male and female rats. To carefully analyze the rats’ health, a histopathological examination of tissues and organs was conducted after the rats died. Histopathology is the examination of organs for disease at the microscopic level (think pathologist doing a biopsy). Histopathological examinations of the reproductive organs, liver, kidneys, and spleen showed no differences between GMO-eating and non-GMO-eating animals.

Three years earlier, a separate group had found the same results for a GMO tomato and a GMO sweet pepper [7]. These researchers had split rats into four diet groups: non-GMO tomato, GMO tomato, non-GMO sweet pepper, and GMO sweet pepper. They fed the rats over 7,000 times the average human daily consumption of either GMO or non-GMO tomato or sweet pepper for 30 days and monitored their overall health. Finally, they carried out histopathology and again found no differences in the stomach, liver, heart, kidney, spleen, or reproductive organs of GMO versus non-GMO fed rats. Despite massive ingestion of GMO potato, tomato, or sweet pepper, these studies demonstrated no differences in the vitality or health of the animals, even at the microscopic level.

Experiments like these on humans would be completely unethical. Fortunately, prior to these studies years of work have demonstrated that rodents, like mice and rats, are acceptable models for humans, meaning rodent responses to drugs, chemicals, and foods can predict human response. Rat feeding studies like these, in which rats are fed a potential toxic item and monitored for adverse effects, are considered both specific and sensitive for monitoring toxicity of foods and widely used in the food regulation industry [1].

The test of time: GMOs and their effect on our offspring

Although scientists have been able to demonstrate that GMOs are not toxic to the animals that eat them, as described above and elsewhere, what about side effects being passed on to our next generations?

To discern whether GMO crops affect fertility or embryos during gestation, a group from South Dakota State University again turned to studies on rats. In this case, the rats were eating a type of GMO corn, more commonly known as Bt corn. Bt stands for Bacillus thuringiensis, a microbe that produces insecticidal endotoxin and has been used as a topical pesticide against insects since 1961 (see this article). To allow corn to directly generate this endotoxin, scientists introduced a gene from Bt into the genetic material (DNA) of corn.

To address buildup of toxicity over time, this group monitored the GMO-eating rats not only for the lifetime of one generation, but also three additional generations. For each generation, they tracked the fertility of parents and compared the health of the embryos from parents that ate Bt corn to those with parents that did not [8]. Toxic effects can arise in many places and in many ways, but some organs are more susceptible to damage than others, and monitoring them is a good readout for other difficult-to-see effects. Testes are considered a particularly sensitive organ for toxicity tests because of the high degree of cell divisions and thus high susceptibility to cellular or molecular toxins.  To examine the affect of Bt corn on testicular health, the researchers tracked testicular development in fetal, postnatal, pubertal, and adult rats for all four generations. The group found no change in testicular health or litter sizes in any generation. Likewise, ingestion by pregnant mothers had no effect on fetal, postnatal, pubertal, or adult testicular development of her offspring.

Other groups have monitored toxicity over time as well. For example, the group studying the bar GMO potato also wanted to see if organs and reproductive health were sensitive to GMOs over long exposure times [5]. To do this, they examined the fertility and gestation periods of GMO-eating mothers compared to non-GMO-eating mothers for five generations. They tracked animal body weight, bone, eye, and thymus development, and general retardation. Like the studies on Bt corn, in all cases, they found no significant differences between the GMO potato and non-GMO potato diets, suggesting that there is no buildup or inheritance of toxicity, even over multiple generations.

Figure 1. Work from independent researchers has investigated various aspects of GMO safety, especially concerning consumer health and toxicity.

Can GMOs change our genes?

Concern has also surrounded the idea that genetically modified DNA would be unstable, causing damage (via unintentional mutations) not only to the crop, but also to whomever would consume it. Mutations in DNA are closely tied to cancer and other diseases, and thus mutagenic substances can have dire effects on human health. The creation of mutations, called mutagenesis, can be measured and compared to known mutation-causing agents and known safe compounds, allowing researchers to determine whether drugs, chemicals, and foods cause increased mutation rates. There are a variety of ways to measure mutagenicity, but the most traditional method is a process pioneered by Bruce Ames at the University of California in Berkeley. His method, now called the Ames test in his honor, is able to track increased rates of mutations in a living thing in response to some substance, like a chemical or food.

To directly test the ability of a GMO to cause mutations, a research group from the National Laboratory of Protein Engineering and Plant Genetic Engineering in Beijing, China applied the Ames test to GMO tomatoes and GMO corn [8]. GMO tomatoes and corn express the viral coat protein of cucumber mosaic virus (CMV). Expression of this coat protein confers resistance to CMV, which is the most broadly infectious virus of any known plant virus, thought to infect over 1,200 plant species from vegetable crops to ornamentals. The results of the Ames test demonstrated no relationship between GMO tomatoes or corn and mutations. They repeated their analysis using two additional methods for analyzing mutagenicity in mice and got the same result, allowing them to conclude that genetically modified DNA did not cause increased mutations in consumers. The modified DNA, like unmodified DNA, was not mutagenic.

Mutagenicity aside, there are also concerns surrounding the ability of the modified DNA to transfer to the DNA of whomever eats it or have other toxic side effects. Depending on the degree of processing of their foods, a given person will ingest between 0.1 and 1 g of DNA each day [9]; as such, DNA itself is regarded as safe by the FDA [10]. To determine if the DNA from GMO crops is as safe to consume as the DNA from traditional food sources, the International Life Sciences Institute reviewed the chemical characteristics, susceptibility to degradation, metabolic fate and allergenicity of GMO-DNA and found that, in all cases, GMO-DNA was completely indistinguishable from traditional DNA, and thus is no more likely to transfer to or be toxic to a human [9]. Consistent with this, the researchers working on the GMO potato attempted to isolate the bar gene from their GMO eating rats. Despite 5 generations of exposure to and ingestion of the GMO, the researchers were unable to detect the gene in the rats’ DNA [5].

A strong argument for GMO health safety

After more than 20 years of monitoring by countries and researchers around the world, many of the suspicions surrounding the effects of GMOs on organ health, our offspring, and our DNA have been addressed and tested (Figure 1). In the data discussed above, alongside many more studies not mentioned here, GMOs have been found to exhibit no toxicity, in one generation or across many. Though each new product will require careful analysis and assessment of safety, it appears that GMOs as a class are no more likely to be harmful than traditionally bred and grown food sources.

Megan L. Norris is a Ph.D. candidate in the Molecular, Cellular and Organismal Biology Program at Harvard University.

This article is part of the August 2015 Special Edition, Genetically Modified Organisms and Our Food.


  1. European Food Safety Authority GMO Panel Working Group on Animal Feeding Trials. “Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials.,” Food Chem. Toxicol., vol. 46 Suppl 1, pp. S2–70, Mar. 2008
  2. G. Flachowsky, A. Chesson, and K. Aulrich, “Animal nutrition with feeds from genetically modified plants.,” Arch. Anim. Nutr., vol. 59, no. 1, pp. 1–40, 2005.
  3., ‘Welcome to the Center for Environmental Risk Assessment | CERA’, 2015. [Online]. Available: [Accessed: 11- Jul- 2015].
  4. Tamar Haspel. “Genetically modified foods: What is and isn’t true”. Washington Post. October 15, 2013.
  5. Jeffrey Smith. “GM Potatoes Damaged Rats.” Genetic Roulette, Section I: Documented Health Risks.
  6. G. S. Rhee, D. H. Cho, Y. H. Won, J. H. Seok, S. S. Kim, S. J. Kwack, R. Da Lee, S. Y. Chae, J. W. Kim, B. M. Lee, K. L. Park, and K. S. Choi, “Multigeneration reproductive and developmental toxicity study of bar gene inserted into genetically modified potato on rats.,” J. Toxicol. Environ. Health. A, vol. 68, no. 23–24, pp. 2263–2276, 2005.
  7. Z. L. Chen, H. Gu, Y. Li, Y. Su, P. Wu, Z. Jiang, X. Ming, J. Tian, N. Pan, and L. J. Qu, “Safety assessment for genetically modified sweet pepper and tomato,” Toxicology, vol. 188, no. 2–3, pp. 297–307, 2003.
  8. D. G. Brake, R. Thaler, and D. P. Evenson, “Evaluation of Bt (Bacillus thuringiensis) Corn on Mouse Testicular Development by Dual Parameter Flow Cytometry,” J. Agric. Food Chem., vol. 52, no. 7, pp. 2097–2102, 2004.
  9. D. A. Jonas, I. Elmadfa, K. H. Engel, K. J. Heller, G. Kozianowski, a. König, D. Müller, J. F. Narbonne, W. Wackernagel, and J. Kleiner, “Safety considerations of DNA in food,” Ann. Nutr. Metab., vol. 45, no. 6, pp. 235–254, 2001.
  10. FDA: Guidance to Industry for Foods Derived from New Plant Varieties, Section V (C).


69 thoughts on “Will GMOs Hurt My Body? The Public’s Concerns and How Scientists Have Addressed Them

  1. Not sure if I missed the answer to this here: is there a good explanation for the mentioned toxicity reports from the early anti-GMO research? Or does one have to just weigh the evidence of the body of work that contradicts them, as done here?

    1. Good question Brian, and this is one of the greatest hurdles to understanding the truth and falsehoods surrounding the topic.

      There are a few issues:
      1.) Many of the “studies” citing GMO toxicity are not actual scientific studies, but anecdotes experienced by someone, almost always not in a research setting. However these are often referred to in blogs or articles as “studies”

      2.) In the case of a peer-reviewed study finding GMOs to be toxic, like the toxic-potato I mention here, it has repeatedly turned out that the work was flawed, poorly carried out and rejected by the scientific community for being bad science. Often a quick google search will reveal this.

      3.) The best way, and admittedly most time-consuming, to discern the truth is just as you said, be informed of all the experiments, their quality, and weigh the results. That is what I have attempted to do here, and it turns out that when only rigorous experiments are examined, they are actually all in agreement. No acceptable scientific study has yet found toxic effects from a GMO.

      1. Wish I had seen this in 2015. Megan, unless I missed it, there was no mention of other ‘organs’ such as the gut. Not the stomach- but the gut..the colon. In your research did you come across widely published scientific proof where a University in California found that a percentage of school-aged children had GMO’s actually in the gut of the child…and I don’t mean in some GMO food the child had consumed, I mean actually adhered in the lining of the gut? You might want to talk with specialists in the area of colorectal surgery. Ask them if they are finding that more and more people under the age of 19 are suddenly popping up with gut problems so horrible (as in a destroyed colon- the entire colon) that the entire gut can not be treated due to the fact that by the time the ‘problem’ manifests to the point of bleeding, it is too late and the entire colon has to be removed or it will burst and kill the individual. There is no margin, no years of gut problems such as colitis or even Chrones- just a sudden need to remove a colon that looks like raw hamburger. This is exactly what my son’s colorectal surgeon said to us….and among his colleagues, one suspect is the consumption of GMO foods. In fact, they have find no other reason thus far. My son went from 185 to 120 six weeks later. He had 4 surgeries and nearly died twice and his heart stopped once on the table- these events were due to the condition he was in. He was robbed of 1 1/2 years of his life due to the surgeries. His hair still has not grown back (3 years later) and at this point he is 21 years old. Not a very picture, is it? I believe one mistake you made is that you did not look for (or find) research done on the ENTIRE body. It appears the information you found was for most organs but certainly not all. You’re young, you’ll learn, but in the mean time don’t lead people down a path pointing to the ‘safety’ of GMO’s. I’m not saying GMO’s are or are not safe, but I am saying at this point the question is ‘WHY’? Why eat something that isn’t necessary to eat (organics can be found and are coming down in price), why purposely eat something that you know has been grown at least with pesticides sprayed on it? What’s the reason…why would people even *want* to do that? It certainly doesn’t taste better, and the ground isn’t allowed to rest using GMO seeds, nor does the GMO (or what’s sprayed on it) nourish the ground…so WHY?

        1. Hi! Can you provide the source from the “widely published scientific proof” from “a University in California” that you mentioned? I would love to read it and maybe even write a follow up to this article about it. Thanks!

          Also–FYI there are plenty of benefits of GMOs that answer your question of why we allow them. Including reducing pesticides when compared to non-GMO conventional agriculture, reducing tilling, and hopefully in the future making crops more resistant to environmental disaster and less destructive to the planet. I’d recommend checking out the rest of our special edition (see link at the bottom of this page)!

          1. Plants aren’t destructive to the planet, it is the way they are raised that promotes destruction. Agribusinesses who unsustainably farm, and overuse pesticides have lead to the requirement for GMO crops and they have largely contributed to environmental damage. It’s a never ending cycle and GMO products are not the solution, merely a quick fix. If natural alternatives were promoted, farms were treated like organisms and not businesses, and sustainable methods were priority this discussion would not be necessary. I like my food from the earth, with its DNA pure, the way it was intended to be.

            Also, if a crop is altered to produce its own pesticides, and the claim is that with GMO crops you are now spraying less pesticides doesn’t the total pesticide count, whether produced internally or applied externally, still add up to non-GMO conventional agriculture?

          2. First, farming itself can be destructive to the plant! Tilling (both organic and conventional!) can cause fertilizer runoff into our water sources, conventional agriculture still uses pesticides. Plants themselves aren’t usually bad for the environment, but growing them in huge quantities like we do to be able to feed the world’s ever-growing population can be. I’m not saying GMOs are perfect. They have their environmental flaws, like the creation of super weeds (see our article on glyphosphate resistant crops in this issue). I’m just saying that GMOs CAN have benefits ESPECIALLY if we learn from our mistakes with first generation GMOs and do better to fix their flaws next time. The population is growing, climate change is happening, and science–specifically genetic engineering–can help us grow food more sustainably in light of these things. Did you hear about the GMO rice that produces 43% more grain and emits 97% less methane ( Therefore helping to both feed more people AND have less environmental impact! This kind of thing speaks to the potential of genetic engineering and the kind of progress that people are stopping by outright rejecting all GMO technology. Yes GMOs we have now have their issues, but genetic engineering is NOT inherently bad.

            Also, GR GMOs don’t produce pesticide. They are resistant to pesticide. One form of GMOs produces insecticide (Bt–we have an article on that in this edition, too, if you’re interested!), but it’s actually the same insecticide that is used by organic farmers (, and I believe there is evidence that the consumer has less exposure to the insecticide in the GM version than when it’s applied directly to plants. A study of these two types of crops did find that these crops allowed for a 36.9% reduction in pesticide use (! Also, glypohsophate, which is used on GR crops is toxic, but less toxic than other pesticides used on conventional crops (see our article on pesticides).

            Given that there is little to no evidence of health impacts of eating GMOs (as in this article) and a potential to help solve a major problem our world faces in the future (climate change, feeding a growing population), I just think that we should give GMOs the chance to help us, as long as they’re properly regulated and researched.

          3. This article is completely biased. There have been no long term studies regarding this issue so how can you claim that GMOs are safe off a three month trial done on rats? Children in the United States are getting sicker and sicker with an increase in allergies, gluten intolerance, intestinal inflammation, and more. I think it is such a shame that Harvard is teaching students to discredit any research that would result in a loss of profits for said companies involved in the making and distribution of GMOs. These companies only care about their profits and do not care about the health of all human beings. Why is it that so many presidents eat organic? Why is it that so many have their own garden full of fresh vegetables and fruit? If GMOs were safe to eat and the government wants the American people to eat it then why wouldn’t the president and his family eat them? Why did Michelle Obama change our children’s lunches into complete garbage? If she eats organic, why would she not put organic food in schools? I think it is sickening that people get paid to lie about what is going on in the world. You all should be ashamed of yourselves. One day you all will have to answer to God for your part in the destruction of the human race.

        2. That’s horrible. Your son has my sympathy. I’m not a doctor but I do have a Bachelor’s in biology and I agree that GMOs may still be the cause of your son’s disease. Let me use an analogy. Asbestos causes mesothelioma, a form of lung cancer. Most people need to inhale a lot of asbestos to get this cancer but a small percentage only need a relatively small exposure to become sick. Your son could be similarly part of a unique minority unfortunately predisposed to become sick.

          Animal models of human disease rarely discover these groups of people in society. We only know of mesothelioma because so many actual people got cancer working with asbestos. Although, it was really only a small percentage of thousands, maybe millions, working with asbestos.

          If we consider your son might be uniquely predisposed, along with the fact that the studies were done on a different species than human, and using GMO crop that humans rarely eat, (GMO soy would have been more appropriate) reasonable doubt about the safety of GMO’s still exist.

          Wish I were a doctor. I’m not.

      2. I would comment that some of the studies sourced for this article are flawed. For example, the “Multigeneration reproductive and developmental toxicity study of bar gene inserted into genetically modified potato on rats”, uses 5% GMO potato in the group fed GMOs to test its toxicity. This is irrelevant to things like corn, where 70%+ of the corn in the US is GMO corn and so our diet, assuming randomized source of corn, will on average have 70%+ GMO in it. I don’t know the numbers for potatoes, but I would be willing to bet that there is more than 5% of our diet of potato is GMO, so the study doesn’t reflect real consumption and would thus not show a real reflection of what are called ‘anecdotal’ evidence. When a farmer is giving feed to his cattle, he is not sitting there measuring out 5% GMO and the rest non-GMO feed for his animals. Furthermore, studies of anything less at least half the life span of the test animal are not useful in predicting long term affects and toxic accumulation — which is what we really care about since people are not slaughtered for food at a few years into their lifespan. The argument that these studies do prove its safe rely on the sort of logic that the tobacco industry has used for years to try to hid that cigarettes deliver carcinogens to the consumer and they may not immediately kill you, but they are not good for you either.

        1. Thanks for your comment–you make some interesting points! You mention only one study cited here, some of the papers cited in this study are metastudies that summarize results of 100s of different studies with different methodologies (some of which feed animals higher levels of GM foods and analyze up to several years–rodent lifespans are only ~2 years), which all suggest that GM foods are safe for consumption. These studies are done by independent academic groups without funding or conflict of interest from biotech groups, making the conclusions different from that of the tobacco industry with regards to cigarettes. (As a side note, from a scientific perspective, there’s also a lot less reason to be suspicious of GM foods since the added DNA and proteins are thought to be broken down similarly to any DNA or protein that you would eat, whereas cigarette smoke introduces foreign chemicals to the body).

          On a more technical note, in the study you mention, the 5% figure refers to the percentage of the rats’ total diet that was made up of potatoes (GM or not GM) NOT the percentage of potatoes in their diet that is GM. Since that particular study is specifically testing potatoes, not corn or other GM products, this actually seems pretty reasonable to me. This would be like a human with a 2000 calorie diet eating about 1 GM potato per day (which I would guess is actually more GM potato than the average human eats, given both the prevalence of potato in our diets and the prevalence of GM potatoes on the market). You’re correct that the average person could have more than 5% of their diet made up of GM foods, but that was not the question of this particular study. Another study cited here (7) actually feeds rats 12-7,100 times the amount of GM vegetable that would be expected to be in human diets, and they still found no health effects by several measures.

    2. The short answer is: the toxic-potato study had design flaws that didn’t allow them to draw any conclusions from their work. One aspect was that their control potato was not equivalent in nutritional value to their GMO potato, meaning a difference in health could just as likely be due to malnutrition.

      1. It amazes me how you consider “your science” the only “right science” and how linear is your way of thinking. Nothing in biology is as simple as you pretend to be and there are many other factors that influence the number and quality of toxicity studies on GMOs. Have you considered ‘funding’ and ‘conflict of interest’ at all in your analysis? I would love to hear from you what exactly is “bad science” and what is “good science”. This is a million dollar question and you would solve all the issues for the scientific community!

        Let me also remind you that 85% of all GMOs are herbicide tolerant and that they were designed to accumulate herbicides and thus going into the food and feed chains.In addition, most of all new GM plants have multiple trait and there is almost no studies that test multiple Bt toxins and multiple herbicides together. This is recognized by EFSA and the scientific community as a knowledge gap. There is a need to study real case scenarios, the food we eat 🙂

        1. Hi Sarah! Thanks for reading! First of all, a lot of GMOs are herbicide tolerant, as you said, but they are not designed to “accumulate herbicide”, but rather resist herbicide. Yes–this can lead to the use of more pesticides on these crops, but the health effects of that on the consumer are unclear. Also, Bt crops actually DECREASE the use of chemical insecticide AND have less Bt (the most common organic insecticide) than organic crops! (See,, and for more info!). Also, plenty (if not all) of the studies cited here are funded by government agencies in multiple countries, as is most basic scientific research, so there should be no conflict of interest. You’re right that most GMOs have stacked traits to be GR and express Bt, and it might be worth testing those two traits together if it hasn’t been done already (I’ll let Megan answer that). However, what is abundantly clear is that the actual process of genetic modification does not make a crop bad for our health–it’s all about what you modify! It furthermore seems unlikely given the current data that any of the GM crops we eat now are dangerous to our health.

          Finally, addressing your first paragraph, many of us at SITN are biologists, and we are aware the biology is complicated! We also believe in trusting data. I am interested in seeing all sides of this issue–if you know of other studies that show that GMOs are dangerous to our health, please let me know! I am always willing to change my mind with new evidence. Untrustworthy science is that without controls that did not go through a peer review process and cannot be replicated (like the IRT study), trustworthy or “good” science is the opposite.

          1. Actually this is patently untrue. Scientific method, the basis of all science, is about testing ideas, hypotheses and theories against new data, ideas and inputs. Sometimes science will be validated, sometimes it will be improved by new thinking, new methodology, new instrumentation for testing, or even whole new theorems. The idea that science is always correct is ridiculous, as all scientific knowledge so far has been for the most part incremental, while sometimes a transformative idea (Einstein’s theory) for instance will upset the apple cart.

  2. I think it is premature to make blanket statements about the safety of GMOs based on the research to date. Some potential holes in the analysis of prior research.

    1. Mice studies are not the equivalent of a double-bind long term human study. Of course you are right that this can not be done but the assertion that mice studies are enough to “prove” safety is not enough in my opinion

    2. Your review of literature show at best that the technique of gene splicing in and of itself is not harmful but this not mean that dangerous & harmful products can be created with gene splicing. Given the infinite permutations of genes that can be combined in the lab it will be only a matter of time that a particular combination will have emergent properties that will be devastating consequences that were not foreseen. With anything, as time goes on business and scientists become lax over time. Mishaps in the Nuclear power industry are a prime example of this.

    3. Lack of studies on population outliers. Sure many products may be safe for the general population but can have very severe consequences for certain segments of the population. Have there been studies looking at particular GMO products against all types of test subjects? Some variables would be pregnant, immune comprised, infant, etc.

    The reason I bring these issues up is that I have two sons. One with a fructose intolerance issue and another with severe allergic GI issues. Per a multitude of studies, the human population is seeing a dramatic rise in allergenic & gastrointestinal ailments in the last 25 years that parallels the introduction of GMO foods. This correlation alone of course does not prove causality but where there is smoke, science must take the time to identify the source of the fire.

    1. That sounds like:
      1. My goalpost is unattainable, and you haven’t reached it yet.
      You mentioned something which cannot be done should be done in order to garner proof. You also are the first person to mention “prove” on this page.

      2. Just because bad things can result from something, does not mean that thing is inherently harmful to you. Nearly everything you do with a positive outcome, has a negative consequence.

      3. Please see the argument written above in the original piece.

      Sometimes there is no fire. Sometimes there is just more understanding. Sometimes, we get better at catching irregularities as time passes. Correlation most certainly does not prove causation, but more-so, correlation doesn’t prove causation especially when it directly contradicts what we already know to be most likely.

    1. “Methods:A meta-analysis approach was employed using electronic databases, current and past journals, and bibliographies of relevant articles. Twenty-seven sources were identified from 2003-2015. Keywords used were GMO testing/methods, GMO health risks, and GMO allergy effects.”

      So they basically googled and didn’t even cite any of their sources. LOL. By “Relevant articles,” do they mean blog posts?

  3. There are some additional things that bother me about GMO’s. DNA and the interplay of the various genes is phenomenally complex. Without even making any alterations in a genome there are many things we do not fully understand about how it all works- what synergies exist, what sequences are key for subsequent sequences to operate successfully, etc. Until I feel confident that we understand more about the complexities of the existing genomes WHEN they are operating within living ecosystems, I do not feel comfortable throwing a wrench into the works. It has taken millions of years for evolution to fine tune these systems- both ours and the plants we are dependent on for food- and there are millions of variables affecting both our internal and external environments. GMO’s feel way too much like playing God. I would rather choose the humbler path of following nature’s lead than the arrogant path, (the one that got us kicked out of the garden of Eden and which is leading us to ruin our second Eden), of tinkering with potentially life threatening technologies .

    My second major issue with GMO’s is that most are “owned” by one major corporation, Monsanto, and the rest are owned by only a few others. Monsanto would have us believe they are interested in GMO’s because they are saving the world, when really Monsanto is just a chemical company (from birth) maximizing profit for shareholders by creating a legal stranglehold on food production. This corporation which is now considered to be a “person” uses GMO’s to make farmers dependent on them to buy their proprietary seed, and then buy their proprietary chemicals, and in addition they sue farmers if they save seed or are inadvertently the victims of wind blown pollen dispersal of GMO’s into other areas on their or neighboring farms.
    If I thought for one minute that GMO’s were actually being utilized to make the world a better place I would seriously look at them as a possible tool, but until they are no longer “owned” by Monsanto and a few other for profit chemical companies I cannot trust the purposes for which they have been designed or utilized.

  4. Too bad this article is complete bullshit. Saying GMOs are completely safe is ridiculous. Who paid for your research Monsanto? Did you get any kickbacks? There is so much evidence saying GMOs are toxic. Look what it is doing to the bee population. Just because someone from Harvard has done a study we should take that as fact?

    1. This article isn’t about one study, it’s about evidence from a bunch of studies (none of which were done at Harvard as far as I can remember). Also, it’s not about environmental effects, to read about the environmental effects you can look here: . We are a graduate student organization, and we’re not paid by Monsanto, and as far as I know, none of the studies we cited here were either. We are merely interested in providing science articles that are based in primary sources (which is what we are doing here).

      Furthermore, there’s actually little evidence that GM crops have had an effect on bees as far as I can tell, but if you have peer reviewed sources that say otherwise, I’d be really interested in reading them! See here to find studies that show that GM crops have no negative effect on nontarget insects:,, . The first one actually shows that Bt crop fields have more nontarget insects than nontransgenic fields.

      1. Also, may I ask if you have gathered any information regarding the disadvantages of GM plants? If you could link some non-commercial studies that aren’t older than 5 years that would be a great help to me.


    2. Hey, I wish that were true Randall. I am actually doing an academic research paper on the positives and negatives of GMOs and let me assure you that there is not many studies proving GMOs are toxic, or harmful for that matter. If there were then I wouldn’t have so much trouble trying to find negatives on this topic. Actually I believe that most of the negatives are just fears that people have concerning the potential risks of GMOs, however, those are just potential risks and have not been proved or agreed upon by a scientific body.
      I’m actually going to have a look on some more articles from this page and see if I can find some disadvantages of GMOs.

  5. I’ve never enjoyed reading a comments section nearly as much as I have this one; for many reasons and peoples!
    I try to be objective when hearing differing sides of an argument and therefore would like to see any credible evidence as to whether or not GMOs are actually harmful to our health; if it’s legit, I’ll listen.

    I’m not yet convinced of the evils of Monsanto, I suspect there is a lot of personal opinions and anecdotes surrounding their reputation and activities. Does anyone know a good, objective source for vetting them a little more thoroughly?

    Lastly, I recently read that the Institute for Responsible Technology (IRT) is not an “institute” so much as a single guy writing blog posts. Does anyone know if this is true?


  6. Would you feed your kids GMOs? Your research is bulshit compared to all the real parents who are witnessing the harmful effects of GMOs on a daily basis. Come do some real studies in the ghetto then maybe you’ll open your eyes to what really is going on.

    1. I agree with the intelligent points in your response . I heard that if you eat lettuce, which contains encoding for green and leafy, your kids can end up green and leafy. Makes sense.

    2. I would perhaps look up the effects of certain food colourings, preservatives and other additives in your diet. There are some nasty chemicals out there completely unrelated to GMO’s

  7. I’m loving to read your series on GMOs. I’ve done extensive research on this matter on the last few weeks and this site has to be one of the most thourough sources there is. That being said, I’m still on the fence about the safety of the use of GMOs to human consumption. The fact is, there is still many things we don’t fully understand about the interplay of gene expression and molecular pathways.

    Furthermore, I’d like to hear your opinion on the following article (Séralini study): I’m aware of all the controversy surrounding said article, being first published in Food and Chemical Toxicology, then retracted and then finally republished in Environmental Sciences Europe, but I read the authors’ answer to critics ( and it seemed plausible to me. So if I could get some unbiased point of view on this, it would be appreciated.

    1. Glad you’re enjoying our articles! First, I’d like to highlight that the science is pretty clear about the idea that genetically engineering food is not inherently bad. For example, newer GMO technologies that are focusing on eliminating expression of certain genes rather than adding foreign genes have very little potential to create food that will be harmful our health. At the other extreme, if you genetically engineered corn to express a gene that make the protein that people are allergic to in peanuts, and then you gave someone with a peanut allergy that corn, they would likely also be allergic to the GE-peanut-corn. So I think it’s important to keep in mind that not all GMOs are equal.

      The Seralini study is somewhere in between these two extremes–they are testing GMOs that have a foreign protein with no known allergenic or negative properties. The summary of my opinion is that there is not enough data to support the idea that there are health effects of GMO crops that are currently on the market, but I don’t think it’s theoretically impossible for a GM food to have negative health consequences, and I fully support continued independent studies.

      I think the first warning sign for this article is that it hasn’t really been replicated by the scientific community, and, in fact, most meta-analysis of many many GMO studies have found opposite results. On a more technical level, there are two red flags that come up for me about this study (and I’m not an expert in his field, but I am a biologist): (1) there’s no dose-response relationship. Usually to show that a substance is harmful, you would show that if you give an animal more of that substance, the effect is greater. So, you’d expect here that if you give a rat a 33% GMO instead of an 11% GMO diet, you’d get more tumors, liver damage etc. But they don’t really see this, which makes scientists worried that they are just measuring noise (or random fluctuations). and (2) the GMO results (GMOs even in the GMO only and not GMO+R condition were at one point treated with roundup) look very similar to the R results, making it difficult to distinguish an effect of genetic engineering from an effect of roundup.

      Here are some responses from scientists who are experts in the field (some in support of and some against this study):

      Hope that helps!

      –Kelsey (SITNBlog Editor-in-Chief)

      1. Oh. Right, I never thought of limiting the expression of genes. They are called “regulator genes” and are introns or exons. They are usually spliced out when DNA gets transcribed into mRNA.

  8. Hi.

    I guess you might be correct on that GMO’s are not linked to Health Issues. I am 14 and got intimidated by a few GMO documentaries a few years ago. I thought that GMO’s were linked to all these health problems, but it seems like, according to you, they were fed 7000x GMO than Human in terms of consumption rates. It seems like if their results can’t be replicated, and that some haphazardly agree and disagree that GMO’s are safe or bad.

    Here is my question: 97% of scientists believe in Global Warming and that it’s caused by Humans. Why then, is it not the case that 97% of scientists believe that GMO’s are safe ?

    Also, GMO’s can compete with Native Crops and outcompete them. That would be bad for the environment. Also, what happens if the GMO plants crossbreed with Native Ones. And since all the Native ones would eventually create their own pesticide, environmental pressures would mean that they would overpopulate and native bugs would die. This would mess up the food chain and lead to a loss of biodiversity. Right ? Also, GMO’s lead to superbugs. GMO’s are like overusing antibiotics, accept they are that on steroids. Evolution will lead to resistance and that means more pesticides and more environmental harm.

    Doesn’t it seem like GMO’s are too complicated. Their environmental impacts are too risky. Especially, if they crossbreed with Native Plants. And what is the advantage of GMO’s ? Why do through all this hassle ? Just eat Organic. If it takes up too much land, use hydroponics. If it raises prices, then work harder and get a pay raise. If Organic means people in 3rd world countries are starving because food is expensive, then tell them to have a 1 child policy and then until they afford it, they can have a 2 child policy.

    1. Actually, there’s very little evidence that GMOs would harm biodiversity (and there’s some engineering tricks that are used to stop that from happening)–see here:

      And you’re right, GMOs can cause super-weeds that are resistant to glyphosphate, but it’s actually from people overusing pesticides (which GMOs make possible)–it’s not an inherent property of all GMOs (some GMOs don’t even have pesticide resistance b/c they’re modified to do something else).

      And to answer your question–data from the AAAS suggests that scientific consensus on GMOs and scientific consensus on human-caused climate change are actually pretty similar (–around 90% of scientists think GMOs are safe and that humans contribute to climate change.

      I personally think we should continue to be careful and test new GMOs to make sure they don’t cause problems with superweeds and biodiveristy, but so far, those concerns are mostly hypothetical.

  9. Hi, I am going to include this research in my argument paper. Thank you for providing a good clarification details regarding the toxicity, genes and mutagenesis. I will cite your research properly and hopefully will have a good feedback to my professor. 🙂

  10. Hi again, another thing is that your references and sources are not up to date. It will actually affect your credibility. Although I took some information that were published after the year of 2012 to make my paper more concise. I still acknowledge and applaud you for your work it is very well written!

  11. Liked the article and the comments. One thing I’d point out as an actual farmer is – the word “super weed” is disengenuous. Some people may associate the word “super” with “super powers”. Glyphosate resistant weeds look just like their non glyphosate counterparts. The resistant plants have just developed ways to stop glyphosate from harming them – through natural selection. No herbicide is 100% effective on all targeted weeds – ie – if glyphosate kills all the susceptible weeds – the only ones that survive a treatment might might be resistant. Glyphosate is quite effective at controlling weeds and it took some time for weeds to develop resistance – but glyphosate isn’t the first herbicide to experience resistance – and not all weed species have developed resistance to glyphosate. Many other herbicides have had target weeds develop resistance as well. Glyphosate has been a very effective tool in our area for reducing soil erosion and preserving moisture in our semi arid climate.

  12. I am not a scientist, just a mom who wants healthy kids. I talk to other moms, many spending huge amounts of their limited income trying to avoid foods that may be unhealthy for their kids, including GMOs. I wasn’t sure if I should he following suit so I did a Google search today and of the top results your a seemed the most reputable.

    I did study agriculture, but I am outdated. But, I do remember finding that organic crops often required elevated total toxicity in order to achieve pest control when compared with non-organic crops since the chemicals at the disposal of an organic farmer are, by nature, limited. So, they sometimes must choose something more toxic than traditional pesticides or use much more of their pesticides to achieve control. I do not remember any sources at this point so everyone can (and probably should) have a heyday with that. The point is that I am familiar with the idea that just because something came directly from nature doesn’t mean its healthy (aflotoxin, cyanide (a pesticide that plants made all by themselves), etc). My question is about Bt crops.

    You said there is evidence that Bt crops actually contain less total pesticide than those sprayed with Bt. However, those sprayed can be washed. I assume you cannot wash the pesticide from Bt crops. But Bt is complex. There may be more to it than I understand. It’s why I ask. Have any studies been done that take washing or rinsing into account, or is that irrelevant for some reason that I do not currently know about?

    Thank you for your diligent research in an internet full of every kind of article and study.

    1. Hi! Thanks for reading! I like that you’re challenging the “natural” = “healthy” idea. I don’t know of any direct comparisons of washed crops sprayed with Bt and Bt GMOs. Actually, though, not all organic Bt treatment can be washed off, since it is sometimes injected (e.g. into squash), which is perhaps why most research has instead focused on toxicity to humans without washing. Bt spray has been considered a very safe pesticide since it was introduced in 1938 ( I’m guessing that there hasn’t been a ton of research about the benefits of washing the Bt-sprayed crops because it’s generally agreed upon that Bt isn’t dangerous to humans (, )–even at the higher doses that people are exposed to if they eat unwashed Bt-sprayed crops. Also, Bt toxin in GM crops is at very low doses in the parts of the plant that we usually eat (e.g. kernel of corn, potato tuber) and is relatively higher in the leaves/stems, which I guess is what the bugs usually eat (

      This article also has some nice info about Bt crops–(search for Bt):

      Hope that answers your question!

  13. I think all of you should look in to foreign studies on this I went through american after america study on this and its left me just unsure, but second I typed in Russian study holy shit I need to look more in to this and other countries that have and have not Banned GMOs. just like Professor Wilson said up the comments the proper research that needs to be done is not there but as I also said I need to look further in to the subject myself I’m doing a research paper on this and I’m eager to learn more. thanks for this article though.

    1. I’d be interested to read anything you find in your search! I have found a difficult time finding studies from any country that convincingly show health effects of eating GMO crops. In this article we cite studies from Korea and China, among other countries. If you’re willing, please share your findings so we can also read these other studies.

  14. Your information and attitude is among the most responsible I have seen. A sign of an objective person.

    I am a research scientist in Agriculture and pesticides- worked on it over 40 years. Pesticides have been proven to be safe and GMO’s have been, as well. Do we know all? Certainly not, but there is a huge amount of data showing safety for both. The negatives are mostly circumstantial or feelings.

    Your comment about human-caused global warming is not true, however. Only about 50% or less of climate scientists think man is influencing climate. IPCC is a group of proponents of man-caused global warming but over 31,000 American Scientists have signed a petition for our government to get out of the Japanese global warming agreement because there is not good data to show that carbon dioxide increases warming. There may be a correlation but not causation. Thanks

    1. Thanks for reading! The data I am citing about scientists’ views on climate change is from the Pew Research Center: and shows that 88% of scientists think GMOs are safe to eat and 87% think climate change is “mostly due to human activity”. I don’t know where your 50% figure comes from (would be interested to see), but the 31,000 people who signed the OISM Petition Project are probably mostly not climate scientists or even practicing scientists, they are just people with at least Bachelor’s degree in any science/medicine field (according to their website–looks like <30% of the people who signed have PhDs).

      1. First of all, I just wanted to say that this article really helped me in my English class.

        Second, I wanted to know if you found a single credible link that gives negatives about GMOs. I think that they are fine and are beneficial, but I’m just trying to find a second opinion

  15. I am doing a pro-con argument on GMO’s and this essay has so many facts and is so well written. I really enjoyed reading it and even the comments on it were interesting to read. It feels like when it comes to GMO’s so many “studies” and “scientific research groups” are just biased groups trying to get people to see only the “bad side to GMO’s” and not any other way. This essay really helped to clear the waters up. Thanks Megan!

  16. Rice, wheat and corn does more than 50% of contribution to the world’s nutritional needs. Wheat alone is consumed as a staple food by 35% of the world’s population. These mega-crops consume significantly more water resources while compared to traditional crops like Sorghum and Millets. Millets are drought resistant and even referred to as “poor man’s crops”. We hear news about drought and food insecurity in African and South Asian countries which, in fact, receive adequate sunlight throughout the year. Is it because these countries move towards the 3 mega crops eventually phasing out the drought resistant traditional crops like millets, sorghum, etc? While we have this interesting debate about GMO’s pros and cons, India is currently facing severe drought due to failure in rainfall. The economy of India is heavily dependent on food exports which majorly includes rice, wheat and corn. And not just export, the consumption of millets and other traditional crops by the people of South Asian and African countries has gone down significantly and the mega crops consumption has increased on the other hand. What’s the solution to these problems?
    There is heavy pressure on such countries to go GMO in order to increase their rice or wheat production despite their water scarcity.
    Is GMO the optimal solution or do we need to pay more attention to food and biodiversity?
    Biodiversity is certainly not in the best interests of companies like Monsanto as it isn’t very easy to commoditize and monetize the drought resistant traditional crops? Even if they find a way out to monetize such crops, it isn’t going to happen overnight yielding immediate profits.
    Shouldn’t we focus more on preserving food and biodiversity as well? What if, change in mindset and investing on native crops has got a better and sustainable solution?
    I am sorry to have brought out the political aspect of this in this thread which is meant only for scientific discussion. For more information on food and biodiversity, please refer to the below link.

    1. We’ve also thought about genetic diversity and drought resistance from a scientific standpoint. See here for more info:

      I think there’s an argument to be made for using genetic engineering technology to make drought-resistant crops. However, it will always be important to consider and test the environmental impact of any newly engineered crops.

  17. I am still concerned about GMO’s. Here’s a link to a document that proves that they are dangerous and debunks GMO-advocate myths:

    Here’s a quote:
    “In a study involving 94 articles selected through objective criteria, it was found
    that the existence of either financial or professional conflict of interest was
    associated [with] study outcomes that cast genetically modified products in a
    favourable light.”
    – Johan Diels, CBQF/Escola Superior de Biotecnologia da Universidade Católica
    Portuguesa, Portugal, and colleagues

  18. Great article! I’m tired of people justifying their “I don’t eat GMO’s” in the possible effects on health! So much people need to read this! What I’m concerned on GMO’s is their impact on the environment, not just directly as crop, but the terrible use of pesticides affecting soil and water (subterranean and water contaminated by run off) since most of them are made to resist glysophate.

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