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.

References

  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. Cera-gmc.org, ‘Welcome to the Center for Environmental Risk Assessment | CERA’, 2015. [Online]. [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).

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

  1. why do people keep mentioning God in this article? most fruits and vegetables people eat today were domesticated by humans.

  2. Downsyndrome is caused by having more or less chromosomes which only occur through chemical or radiation. Eating foods don’t change your DNA. GMO causing Downsydrome is just a internet rumor.

  3. this realy upsets me because i eat tons of fast food and i love to drink ice cram shakes i love fast food gmo foods is wrong

    1. Judging by the way your comment is written, you are 9. If you eat tons of fast food, you WILL get type 2 diabetes, which is obviously bad for you. I don’t understand what you mean by “gmo foods are wrong”. Is eating GMO foods morally wrong or is the production of GMO foods wrong? Also, fast food by default (excluding restaurants like chipotle) do use GMOs because its cheaper than organic ingredients. 🤣 GMOs have been going on for the past 50+ years btw.

      1. If they are “nine” then why respond? They are clearly grammatically incorrect but you can still understand what they are attempting to say. Do you feel special belittling someone who is “nine”? Grow up. Using emojis like that is childish, so you have no room to tell anyone anything. GMOs started being used in food during the mid 1990s so your incorrect, “50+ years”, if your gonna belittle anyone get your facts straight.

        1. Just my thoughts on the topic. But haven’t genetic modifications been going on for hundreds of years, in the form of selective breeding.

  4. This article is deceitful… either that or very ignorant.

    -Overall, the article says that that studies show that GMOs are safe.
    -It talks about how healthy GMO potatoes sweet peppers are.
    Great! Way to only talk about which GMOs are good.
    -It in vaguely discusses how bt corn is safe and tries to sound justified.

    What is it missing?
    -So much!
    -There is no data supplied. There are No numerical values.
    -It doesn’t mention the effects of bt corn on the organs of mice at there time of death (which is when the data matters the most). Instead after discussing more about the end results of GMO corn on mice or rats, it loops back to mentioning how safe GMO potatoes are. Confusing…
    -It doesn’t mention why bt corn is so bad for ones’ health and what specific health issues bt corn has been associated with (especially for mice and humans that are middle aged or elderly – that when experience the health issues the most – the later years of life). In the research, data for the mice looks great for the first half of their life! But the second half isn’t reported. If I recall, that was originally a study done by Monsanto, making this very biased.
    -bt corn is engineered to be a living pesticide and has been linked to leaky gut syndrome, more than one type of cancer, and several other health issues. Very little is reported about how these GMOs affect the nervous system, brain health, and mental health.
    -The paper also doesn’t bother to mention the health impacts of longterm exposure to any chemicals that are sprayed on these GMO plants. And yes, they really do cause cancer… look up Roundup spray health risks and lawsuits. That’s one major reason you want to throughly wash your vegetables before you eat them.
    -While your at it, look up bt corn lawsuits.
    -These companies will sue people who talk badly about their product. Look up how Oprah Winfrey was sued to making a comment on how bad corn syrup is. She fought the league battle, spent millions to prove her claim, and won the suite. If she didn’t have the money, she would have lost, even though she was right. In the end it’s all about money…

    There are plenty of sources on the web that talk about how safe GMOs are (even on .gov websites). But if you want the truth, you need to actively search for the truth that is buried. What drives people to write these kinds of articles?? Money and/or ignorance

    What is your motivation for writing this paper?
    Aren’t there already enough websites already out there telling us how safe GMOs are.
    This paper very one sided.
    Do we really need one coming from harvard.edu?

    1. I labored thru the reading of study results. I so agree with Adam, having little but, God given instincts and pretty decent common sense. Not a scientist. Just a Mom. I see what science has done the last 4 or so years. Also the antics of Haaa vaaad. I’ll take Adam’s opinion any day.
      I agree with him 💯. I couldn’t care less for myself hitting my 8th decade soon. My younger people matter to me, I will stay on this research.

    2. WE JUST DON’T KNOW HOW DECEITFUL !!!!!!!!!!!!! IN 2023-24 , MOST PEOPLE CAN BE BOUGHT FOR MONEY AND PROFIT , INCLUDING JURORS , SCIENTISTS , ETC . !!!!!!!!!!!!!!!!

    3. myers you’re clutching here! i was wondering if nothing was really wrong with gmos for a high school paper but you informed me! thanks dude!

    4. Man, calm down about that corn “if I recall”. Next time you criticize anybody at all (let alone about a lack of evidence) get some actual evidence of your own.

    5. Also, bringing up legal issues when it comes to GMOs isn’t at all relevant. For example: somebody once went to court claiming vaccines made spoons and other metallic objects stick to their face. Did a spoon actually stick to their face? No, absolutely not.

  5. For those wondering, as of 2024 this information, insofar as I have been able to confirm, is up-to-date. As a member of the life sciences community, I have some perspective on this topic and would like to make it clear that there have been studies done on humans as well, they just aren’t as frequently cited because they aren’t controlled studies. You can’t intentionally do a study on humans that might lead them to harm they would otherwise never encounter, but you can query people on their dietary habits and then test their health. This has been done quite a bit in the last few years, with the findings, once again, showing the safety of GMFs.

    For people that might believe it’s better to be cautious and just cease research into GMFs, I’d like to offer some insight there as well. Keeping ahead of pests, disease, drought, and other potential famine events is and always has been a constant struggle in agriculture; GM is primarily a tool for continuing this fight and feeding an ever-growing population. Options are always being explored, and safety concerns are always paramount, but stopping progress simply because the public doesn’t understand it is an unreasonable ask.

    To be clear, I think people should constantly demand transparency and should always be vigilant of motives, concerning practices, and unethical behavior. I find nothing disagreeable about the concerns themselves, and everyone is also entitled to know what they’re eating, why they’re eating it, and to choose for themselves whether or not they should eat it. But I feel that that sort of autonomy comes at a price – if you truly want to make such informed decisions and not let others make it for you, you need to be able to gather the necessary information. That’s what scientists and researchers are there for – to give you data and analysis that you can, ideally, rely on so you don’t have to gather it yourself (nor be trained on how to do so). But, as this article alludes to, not all sources of data and analysis are created equal. So it requires looking to more than one place, verifying sources, etc. if you truly want to maintain that level of informed.

    Excuse my soapboxing, I just noticed that this comment section on a rather helpful article was largely filled with questions, misinformation, and fear. I can’t and don’t want to respond to every concern or convince everyone of what is safe and healthy, but I figured I could be one more voice advocating for the formation of informed stances.

    1. ANYTIME MANKIND GETS AWAY FROM THE WAY GOD JEHOVAH CREATED THE NATURAL ORDER OFTHINGS , IT BECOMES AN ABSOLUTE MESS !!!!!!!!!!!!!! IF MANKIND HADN’T REBELLED AGAINST JEHOVAH , WE WOULD NEVER LACK THE THINGS WE NEED ON EARTH !!!!!!!!!!!!!!

      1. 1. Take a chill pill like the other guy said below
        2. Jehovah’s witness is a cult, you are being brainwashed, please get out of it.
        3. This comment has nothing to do with GMOs. This one’s sanity must have already crumbled.

      2. as a fellow christian, I would like to disagree. there is truly not much wrong with GMOs, and mentioning the natural order of things is ridiculous. God gave us grapes and we made wine, with the things he gave us. it is not a disgrace, it is use of our god-given resources.

  6. Thank you for this clear, thorough, and well-cited summary. There are a lot of claims about GMOs online that simply have no basis in science, and I’ve been looking for reliable information based on the consensus of experts in nutrition and medicine.

      1. Right at the end of the article if you even read it, it states all the reference to all the sources they used.

    1. To answer the question as to who sponsors these studies, everyone. As the article states, these studies have been done all over the world by countless researchers and the broad body of results keeps confirming the same thing, GMOs as a class are just as safe as other foods as a class. There is nothing special about GMO foods that makes them uniquely dangerous to human health.

      That makes sense, of course, because other foods have had their genomes modified by humans as well, even those labeled as organic. I’m fact, a much larger portion of the genome has been modified in comparison. One technique that has been used since before the current technology that people think of and call GMO, is to blast the plants with large amounts of radiation, the kind of radiation that will affect DNA, it causes a bunch of mutations to occur and then the resulting crops are tested for desirable changes. Such crops can and are labeled as organic foods. The new technology modifies much less of the DNA, and doesn’t create numerous unexpected and potentially undesirable changes to the genome. It’s like a scalpel vs a sledgehammer. So the results that GMOs are generally safe corresponds with our experience that irradiated food is generally safe. To the extent that any food is safe that is, there will always be cases of specific crops being unsafe, regardless of GM, and we experience alerts & recalls all the time when those occur, typically due to contamination.

  7. My notes are:
    1 – All experiments carried out on rat or mice not human !! because unethical as researchers said above
    2- is diagestive system of lion or hyena smillar to human ? Definitely not because these animals eat cadaver without damage but for human die after
    1 to 4 days without health care.
    Then rat or mice different from human
    3- why rich people eat organic or even traditional food but not GMO food ? . As we no GMO more cheaper than other types of food
    4 – The most unethical issues are change in DNA for any living material ( animal or human or plants ) because these things are GOD or Nature specialisty not human . Human can develope any thing on this earth except a live material such is ships , cell phone transportation , life improvement
    ….etc

  8. More gaslighting from the Government. They couldn’t provide any evidence that the GM foods have any risk. How about pointing out they can’t prove they don’t? Wouldn’t we err on the side of caution over the profit margins of multibillion-dollar corporations? Let’s just look at what happened with the unsafe covid vaccine. That was safe. Right?

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