How Did GMOs Become So Controversial?

It's hard to find an issue as politicised and polarised as genetically modified organisms (GMOs). For some, GMOs represent the promise of a better future; for others, they embody the ultimate expression of human arrogance–manipulating nature in ways that threaten to deplete our planet’s resources and harm our health.

The divide in beliefs about GMOs is clearly represented in the contrasting views between scientists and the general public. In 2015, 88% of U.S. scientists agreed that GM foods are safe to eat, while only 37% of U.S. citizens shared this view.¹ By 2020, the number of Americans considering genetically modified foods safe to consume had dropped to 27%.²  In the European Union, people have generally distrusted GMOs, but in recent years, public trust has slowly increased. Still, more than one third of citizens in several countries – Czech Republic, France, Germany, Italy, Poland, Spain, and Sweden – remain concerned about GMOs. However, European policies are still inconsistent with this growing trust: 16 out of 27 European Union countries have banned the cultivation of GMOs, while they continue to import around 118 GMO products, primarily for animal feed, but also some for human consumption.³,⁴

The top GM crop grown in 2015 was soybean (92.1 Mha), followed by maize (53.6 Mha), then cotton (24 Mha) and oilseed rape (8.5 Mha). This represents 83% of the world production of soybean, and 75% of production of cotton. Photo via Getty Images.

How did we arrive at this common ground of contradictions? Diving deep into this topic revealed something crucial: the real question isn’t whether one is for or against GMOs, but rather how this technology is used. The controversies are real, they stem from the types of GMOs agro-companies produce, the ways GMOs are implemented, and their impacts on society and the environment. In this deep dive, I’ll attempt to unravel these complexities.

What does it mean to genetically modify?

To understand GMOs, we first need to grasp what it means to genetically modify an organism. This quickly leads us into controversial territory, as science and the law offer different definitions.

The scientific definition

From a scientific perspective, humans have been genetically modifying animals and plants for thousands of years, selecting traits like high crop yields in certain plants, or even loyalty in dogs.⁶ While the idea of genetic modification might seem complex, understanding DNA helps demystify it. For any organism, all traits you see (and those you don’t) are encoded in its DNA, which functions like a recipe book.⁷ Each "recipe” is a gene, written with the same alphabet composed of four "letters"—A, T, C, and G. This four-letter alphabet is the same for every organism on the planet, but the order in which the letters appear results in our differences. We humans, for example, are 99.9% identical, and it’s only that 0.1% that makes each of us unique in the world.⁸ Historically, humans have used three main methods to modify the genes of plants and animals:

Crossbreeding
Until the end of World War II, the primary method of genetic modification was crossbreeding, which involved selecting and breeding plants with desirable traits. For example, a drought-resistant rice plant might be bred with one that produces tasty rice—with the hope of combining both qualities. However, this method is slow, unpredictable, and offers no guarantee of success. Although crossbreeding genetically modifies species, it's not legally considered a “GMO”, because it simply accelerates a natural process that could occur over longer time periods without any human intervention.⁹

Tenderstem broccoli is a hybrid of Chinese kale and broccoli which was first introduced in Japan in 1993. Chinese kale is a leafy brassica with long stems that it lent to the broccoli, resulting in a broccoli floret with a stem that is totally edible, even when raw.

Mutagenesis
After World War II, scientists began using nuclear radiation to induce mutations in plants. This technique, called mutagenesis, produced new traits, some desirable, like pest resistance.¹⁰ For example, the wheat variety "Creso," used in much of our pasta and pizza, was developed through gamma ray bombardment.¹¹ More than 3,000 plant varieties worldwide have been created this way, but under European law, they are not classified as GMOs.¹²  That’s because mutagenesis can also occur naturally without human intervention: exposure to cosmic rays, UV light from the sun, and environmental chemicals, all of which can cause spontaneous changes or mutations in an organism’s DNA. Moreover, this method of genetic modification is explicitly exempt from the scope of the EU's GMO legislation due to its long history of safe use. And so, regardless of the spooky origins, new varieties created through this process are deemed safe.¹²,¹³

The wheat variety "Creso," used in much of our pasta and pizza, was developed through gamma ray bombardment - a type of mutagenesis.

Transgenesis
The key legal distinction for when genetic modification becomes ‘GMO’ is when it occurs through a process called transgenesis. Introduced in the 1970s, transgenesis is a process where genes from one species are actively inserted into another. This method allows for the transfer of DNA between species that wouldn't naturally interbreed, such as a mosquito and a rice plant. Unlike earlier methods, transgenesis is precise, allowing scientists to control exactly what changes are made in the DNA.¹⁴

Bt-corn is a genetically modified crop. It contains bacillus thuringiensis, or Bt, a common soil bacterium whose genome contains genes for several proteins toxic to insects.

The legal perspective

"The current legal definition [GMOs are organisms (apart from human beings) whose genetic material has been altered in a way that does not occur naturally by mating and/or natural recombination¹⁵], has the advantage of drawing a clear line at doing something that wouldn’t occur in nature, which could be a good boundary," said Mauro Mandrioli, Genetics Professor at the University of Modena, in a video call. "But the downside is that I’m not sure the public fully understands this definition." In other words: labelling something as ‘unnatural’ makes it seem frightening. This definition is being challenged by New Genomic Techniques (NGTs), methods of genetic modification that began to emerge in the early 2000s and have been continuously refined over the past two decades. Unlike traditional methods that transfer genes between species, NGTs directly modify the genes in question.¹⁶,¹⁷

We’ve covered NGTs and the new EU policy here.

In this article, I want to delve into how GMOs became so demonised, beginning with the most common concerns.

Which health risks are associated with GMOs?

Health concerns surrounding GMOs often focus on the potential risks of toxicity, allergic reactions and gene transfer from GM foods to human cells or bacteria in the gut, which could be a concern if it negatively impacts health.^18,19 To address these concerns, companies producing GMO foods must conduct thorough and costly safety tests, sometimes taking years to complete.¹⁸ These tests are designed to catch any harmful products before they reach the market. For example, when Pioneer Hi-Bred International found that their GM soybeans contained a substance linked to peanut allergies, the product was never released.²⁰

In addition to industry tests, many independent studies have also been conducted to assess any potential health risks associated with new GMOs. In 2010, the European Commission reviewed 50 studies on GMOs funded over a decade, finding "no scientific evidence linking GMOs to higher risks for health or the environment.”²¹ While this doesn't mean all GMOs are automatically safe, it suggests there is no well founded support for automatically distrusting them either. GMOs are made from the same basic building blocks as any other organism. The key to safely exploring GMOs is to assess each one individually. As the World Health Organization states, GMO food safety should be evaluated on a case-by-case basis.²² In other words, there’s no universal "GMOness".

As genetics professor Mauro Mandrioli explains, "A [GMO] product's safety depends not on the method used to create it, but on the specific changes made." Ironically, GMOs have undergone far more safety testing than other foods, definitely more than those created through mutagenesis, which involves gamma ray exposure. They have also been studied more extensively than recently popular novel foods like goji berries or chia seeds, which were either overlooked for centuries or never common in Western diets.

Despite overwhelming evidence from comprehensive reviews, such as those by the European Union, many still fear GMOs, arguing that "you never know what could happen in the future." Italian geneticist Edoardo Boncinelli gave me his perspective on the phone: "There's always a margin of uncertainty. Some may say they aren’t willing to accept any risk, but daily life is full of small risks—whether crossing the street, taking medicine, or driving. As Boncinelli puts it, "If we go through life with 'you never know,' we'd never do anything. I left the house this morning, and anything could have happened. Should I have stayed home?" In other words, yes, there are risks. But they are lower than those we usually accept in our daily lives.

What are the environmental concerns? 

Environmental concerns about GMOs are often more serious than health concerns because the science is less conclusive. This is partly due to a lack of standardised methods for measuring environmental impacts and the ethical considerations surrounding the potential consequences of altering ecosystems. A common worry is that GM crops might mix with traditional crops, creating unwanted traits or spreading uncontrollably, outcompeting wild species and impacting global biodiversity.

Read more on biodiversity in How Fig Trees Restore Forests and Biodiversity

Cotton harvesting in Mississippi, USA. This BTC farm raises 1000 acres of cotton, 80% of which is genetically modified Bt, Roundup Ready cotton. The US government mandates at least 20% of the crop is planted with conventional cotton to help prevent insects from developing an immunity to the GM products. Photos via Getty Images. 

For now, several meta-analyses, including a review of 850 studies, have found that GMO crops haven't had more negative environmental impacts than conventional crops.²³ Simple precautions, like buffer zones to reduce pollen spread, can minimise these risks.²² That said, several studies suggest that some GM crops producing insecticide toxins (like the Bt corn I mentioned earlier) have increased risks to moths and butterflies in nearby fields, which need more research. But again, the Royal Society in England, similar to the WHO's stance on health, concluded that the impact on biodiversity depends more on the specific traits of the crop than on how it was created.²⁴

The EU’s GMO Confusion 

At this point in my research I felt quite confused. I could understand the initial resistance to GMOs given the few and inconsistent studies at the time. But I couldn’t grasp the decisions made by EU countries. In 2015, the European Union decided it would authorise which GMOs could be grown, but left it up to member states to choose whether to plant them. In response, 16 out of 27 countries immediately banned their cultivation.²⁵

I puzzled over this for days, wondering how such a seemingly unscientific decision could be made when decades of reputable studies were already available. Searching for what else might have influenced this choice, I found the answer: glyphosate. Glyphosate is a herbicide used to kill weeds and grasses. It works by blocking a key enzyme that these plants need in order to grow. Glyphosate isn’t a GMO, but it plays a big role in why GMOs continue to have such a bad reputation. As I delved deeper into the history of glyphosate, it became clear that this narrative has less to do with science and more to do with power.

The story of Monsanto

Monsanto is a company whose name is synonymous with GMOs, and frankly, is central to understanding the anti-GMO sentiment we’re feeling today. It started in 1901, when American businessman and chemist John Francis Queeny founded a company and named it after his wife, Olga Mendez Monsanto.²⁶ The company started by producing saccharin, a sugar substitute, but within 60 years, it was manufacturing aspirin, nylon, plastic, and pesticides.²⁷ Monsanto wasn’t about specific products; it was about chemical synthesis—creating anything with the promise that modern technology could improve our lives. However, Monsanto's involvement in controversial projects tarnished its reputation. The company participated in the Manhattan Project, producing plutonium for the Nagasaki bomb, and later supplied herbicides for the U.S. military during the Vietnam War, contributing to environmental devastation.^28,29 Rachel Carson’s 1962 book Silent Spring exposed the harmful effects of pesticides, including those made by Monsanto.³⁰ In the 1970s, Monsanto's flame retardants, PCBs, were found to be carcinogenic.³¹ These revelations severely damaged the company’s image and fueled public distrust.³²

To rehabilitate its reputation, Monsanto transformed into an agrobiotech company. It shifted its focus to developing genetically modified crops and patenting technologies to protect its market position. In the 1990s, it introduced RoundUp Ready: a package combining glyphosate, a herbicide, with GMO seeds resistant to it.³³ This allowed farmers to use herbicide freely without harming their crops–but it was also, however, a direct affront to concerns about excessive chemical use. Roundup was launched in 1996 amid controversy. Initially, the U.S. Environmental Protection Agency classified glyphosate as a possible human carcinogen, but later changed its stance.³⁴ Over time, public and political resentment grew toward Monsanto and other major agricultural companies, collectively known as ‘The Big 6’ (now the Big 4 after mergers), due to their increasing market concentration.³⁵ The real issue was for a long time social and economic, such as the effects of Monsanto’s seed market control on farmers and food prices. Then 2012 came, and a flawed French study claimed that glyphosate caused tumours in mice, reigniting fears. Although the study was first retracted and later republished–retaining its controversial status–the damage was done, and by 2013, protests against Monsanto erupted globally, with signs reading "NO GMO".^36,37

It’s a trust issue

The final blow came in 2015 when the WHO classified glyphosate as "probably carcinogenic to humans."³⁸ Let’s see why. In 2017, a study linked glyphosate to liver disease, and in 2018, Monsanto lost a lawsuit to a Dewayne “Lee” Johnson, a former school groundskeeper who claimed that the glyphosate in RoundUp Ready caused his terminal non-Hodgkin's lymphoma, costing the company $289 million.^39,40

Remember: Glyphosate isn’t a GMO; it’s a herbicide that Monsanto’s GMO seeds were designed to resist. But they were sold together, and their destiny would inevitably be intertwined.

During the trial with Johnson, documents known as the "Monsanto Papers" were revealed. These showed that Monsanto had paid researchers to review scientific literature, but asked them not to disclose conflicts of interest.⁴¹ Monsanto also selected which researchers would handle the reviews and even influenced them by saying, "Based on your criticism, we'll decide whether to extend or end your involvement."⁴² Monsanto avoided studies requested by regulators and had connections within agencies like the US Environmental Protection Agency.⁴³ One EPA contact even joked about getting a medal for burying unfavourable information.⁴⁴ Monsanto built ties with journalists, had them review articles before publication, and paid Google to promote results that discredited critics like investigative journalist Carey Gillam.^45,46

In response to the growing controversies, the EU introduced a transparency law in 2014, requiring companies to register all studies you intend to carry out on a product before it can be authorised, and in 2018 implemented a Clinical Trials Register.^47,48 This prevents companies from cherry-picking only the studies with favourable results. But it was too late, and trust had already been lost. When the WHO labelled glyphosate as potentially carcinogenic in 2015, the same year Europe allowed member states to decide on GMO cultivation, and 16 out of 27 states opted to ban GMOs.⁴⁹

This reaction is understandable: although glyphosate and GMO seeds are two different things, they were sold together by Monsanto. Given Monsanto’s history with carcinogenic PCBs, harmful herbicides used in Vietnam, and the revelations from the Monsanto Papers, it became natural for people to extend their suspicion to GMOs, fearing that the full truth about them had yet to emerge.

A banner reads, 'Monsanto & Co. Get Out !' at a march against Monsanto-Bayer in Toulouse, France 2022. Protesters say they 'refuse the toxic world of Monsanto-Bayer' as scandals and justice procedures against the companies become more frequent. Similar protests took place elsewhere in France. Photo via Getty Images.

My final thoughts

After reviewing the history of the GMO debate, it’s clear that banning the cultivation of GMOs while still importing them doesn’t make sense—if GMOs were considered dangerous, they should be banned entirely. However, with the scientific evidence and advanced tools we now have, it’s evident that GMOs should be evaluated on a case-by-case basis. Blanket opposition to GMOs is as illogical as rejecting all medicines because some may have side effects. The real issue doesn’t seem to lie in the technology itself, but in how GMOs are used, marketed, and regulated.

So perhaps what we need is more independent research and less control by the few companies that dominate the market. At the moment, GMOs hold potential benefits such as improved nutrition and resilience to climate change, which remain largely unexplored. Even in the US, where regulatory processes are more flexible, companies have prioritised traits related to yield and pest resistance over nutritional enhancement and resilience to climate change. In a world facing severe climate challenges and widespread hunger, the true tragedy would be missing these opportunities because we were unable to separate useful technology from the market monopolies that currently control it.