Confused about the mixed messages on GMO foods? Here’s what the evidence says

Genetically modified foods have been met with consumer backlash since they were first introduced in the 1990s. Recently, however, calls for non-genetically engineered options have gotten even louder.

In April, Major North American fast food chain Chipotle announced it would endeavor to provide non-genetically engineered menu options (which is, albeit, not 100% possible). This past summer, celebrities including Jordana Brewster and Ginnifer Goodwin signed on to a campaign calling on U.S. food companies to reveal ingredients derived from genetically modified organisms (GMOs). And the New Democratic Party of Canada has recently called for labelling of genetically modified foods.

These campaigns are based on concerns that GMO foods might not be safe for consumption or could damage the environment. Anti-GMO proponents claim GMO foods are linked to everything from cancer to allergies. The David Suzuki Foundation’s website warns “a growing body of research connects [GMO] foods with health concerns and environmental damage.” (A media representative of the David Suzuki Foundation explained that the Foundation couldn’t provide an interview because none of the scientists at the organization are currently researching GMO foods.)

In contrast, major governmental and health organizations, including Health Canada, the European Commission and the Food and Drug Administration, have examined hundreds of studies and concluded that there is no evidence GMO foods are any less safe for consumption than conventional foods.

When the independent non-profit PEW Research Center asked scientists and members of the public about their views on 13 commonly debated topics, genetically modified foods was the issue that divided scientists and the public the most. In the 2015 poll, 88% of scientists polled across an array of disciplines responded that GMO foods are safe, while only 37% of the general public believed they were safe.

We look at what the evidence says about the GMO foods that are currently on the market.

What are GMO foods?

Genetically modified foods are foods that come from plants with DNA that has been changed in a way that does not occur naturally by conventional or modern breeding techniques. This could mean changing the way a gene in a plant behaves, or inserting one or more gene into the genome of a plant, which contains tens of thousands of genes. The inserted gene, which might be derived from viral, bacterial or plant DNA, is added because it contains a desired trait.

While food can be modified for a variety of reasons, including to make it more nutritious, the genetically modified foods we’re exposed to have generally been modified for two reasons, according to Rene Van Acker, professor and associate Dean of the Ontario Agricultural College at the University of Guelph. “The traits that we’re talking about that are GM-conferred are herbicide tolerance or insect resistance,” says Van Acker. With genetically modified corn, for example, a bacterial gene is inserted because it produces a protein that is toxic to some insects, but not to humans.

One major exception, points out Andreas Boecker, a professor in Food, Agricultural & Resource Economics at the University of Guelph, is the Hawaiian papaya, which was facing extinction before it was genetically modified to be resistant to the virus killing it.

One of the biggest misconceptions of GMO foods is that “almost all produce is genetically modified,” says Van Acker. Because genetic modification is expensive, the technology is only cost effective when applied to large-scale crops, such as wheat, soy, canola and corn. So while the tomatoes we buy aren’t genetically engineered, more than 90% of soy growing in the US is genetically modified to tolerate herbicides.

What do we know about the safety of GMO foods?

Before a genetically modified product can be sold to farmers or consumers, the company producing the GMO food must perform numerous safety tests and submit nutritional and allergenic information on the product to Health Canada. According to Brian Ellis, a professor in the Department of Botany at the University of British Columbia, it’s a process that takes years and is extremely expensive. “The approval process can cost over $100 million dollars to bring a really new genetically modified product to the market,” says Ellis. “Most of that cost is the testing.”

Safety testing is meant to screen out products that could be harmful. For example, when soybeans developed by Pioneer Hi-Bred International were found to have the same chemical that causes peanut allergies, the product was abandoned and never went forward to market. None of the GMO products thus far approved have been shown to have any adverse health outcomes.

“These foods have undergone more extensive testing than any food that has come on the market,” explains Joe Schwarcz, professor of chemistry at McGill University and director of the Office for Science and Society.

In addition to the industry tests, numerous independent studies have been conducted. In 2010, the European Commission released a summary of 130 research projects on GMO foods that had been funded by the Commission over a decade. The studies revealed “no scientific evidence associating GMOs with higher risks for the environment or for food and feed safety than conventional plants and organisms,” according to a press release from the organization. A systematic review of animal feeding trials (both industry and non-industry funded) also concluded GM plants to be safe.

As with fluoride in water or vaccines or almost any health-related technology, some animal studies have been used to suggest that GMO foods could cause harm to human health. These studies are too methodologically flawed, however, to prove anything.

Some scientists and anti-GMO activists argue that GMO foods cannot be seen as safe because epidemiological or large-scale randomized controlled studies in humans haven’t been carried out.

Schwarcz points out that even though “we’ve been eating these foods for 20 to 25 years,” it’s possible “there is some subtle health affect and we wouldn’t know it because we live in such a complex world.” He is quick to point out, however, that “we know a lot” about the safety of GMO foods. “Based on what we know about the technology involved, and based on what we know about the body, it’s extremely unlikely.”

Should we be worried about GMOs damaging the environment?

More prominent than the health concerns with GMO foods are the environment-related fears. Here the science is more contested, especially because the scientific community has not agreed on standardized methodologies when it comes to measuring environmental impacts.

One review of around 850 studies concluded that genetically engineered crops have not had more negative environmental impacts than conventional crops. But some studies have raised potential risks – such as to moths or butterflies in surrounding fields – that require further research.

An especially polarizing environmental issue is whether GMO crops increase or decrease the use of chemicals in agriculture. In explaining its decision not to use GMO ingredients, Chipotle cites a study that estimated pesticide and herbicide use increased by more than 400 million pounds over four years due to GMO crops. The study was conducted by a scientist funded by the organic food industry.

One European government-funded review of 147 studies came to the opposite conclusion, finding that GMO crops had resulted in a 37% drop in pesticide use. While many of the studies were industry funded, the researchers analyzed the studies by funding source and found industry funding did not “significantly influence the impact estimates.”

Van Acker is of the opinion that more long-term studies are necessary to see if GMO foods increase or decrease herbicide and pesticide use. He explains that while GMO crops initially result in less chemical use, as weeds develop resistance or GMO crops spread into unwanted areas, pesticide and herbicide use can increase over time. He explains, however, that once GMO crops begin to require more expensive chemicals, farmers tend to stop using them. “Farmers are not pro-GM crops or anti GM-crops,” says Van Acker. “They’re pro-whatever is good for their business.”

Sylvain Charlebois, currently a visiting professor at the University of Innsbruck in Austria, says that it’s important that governments and independent institutions continue to fund studies on the environmental and gene flow effects of GMOs. “It’s important to make sure that we assess longitudinal, environmental risk, and that’s hard to assess in a lab,” says Charlebois. Boecker agrees. While he is sympathetic to arguments that GMO science is too heavily dominated by industry, he argues that rather than restricting or labelling GMO foods, the debate should instead focus on “how much do [independent research institutions] need to invest in risk assessment and management to make risks acceptable?”

Why is there a disconnect between scientists and the public on GMO foods?

 The science thus far tells us that GMO crops don’t pose a risk to human health and could have both positive and negative environmental affects that need to be continually monitored and mitigated. So why do most consumers feel GMO foods are dangerous?

Partly, the public opinion reflects “a fundamental distrust of science and technology,” says Ellis. “It’s a thread that runs strongly through our society still.” One recent survey found that while 72% of respondents think it’s important to know science in their daily lives, a third of respondents believed scientists adjust their findings to get the answers they want. Inaccurate reporting of science relating to GMO foods in mainstream media and blogs hasn’t helped.

Stemming from this distrust is the belief that there is something intrinsically bad about human interventions in natural processes, explains Schwarz. “Nature is not exactly benign,” he says, making reference to “viruses, bacteria, natural carcinogens, alfatoxins.” Plus, he says, the movement of foreign genes into plant DNA is not so contrary to nature. “Humans are constantly exchanging genes with bacteria,” he explains.

But Charlebois says GMO producers are also to blame for the confusion. In a case study of Monsanto, Charlebois found the company allowed distrust and ill will to proliferate because the company largely ignored the public, instead engaging with farmers and agricultural industry stakeholders on GMO science. “They were selling a product without really engaging with consumers,” he says. Though he admits the distrust of the technology is partly due to a general distrust in the major corporations that use it, Charlebois argues that the “Frankenfoods” fears could have been better countered had industry scientists engaged with the public through the mainstream and social media.

Perhaps learning from the importance of public dialogue, Arctic Apples, the company behind the non-browning apple recently approved for sale in Canada, prominently explains on its website how biotechnologists modified the apple by turning off the activity of certain genes. Commonly called “gene editing,” this practice is different from transferring foreign genes into a genome, but Ellis predicts that gene editing will become a more common method of genetic modification in the future.

In the end, trust in GMO foods may have less to do with the science and more to do with how that science is explained – by the media, by scientists and by industry representatives. “The activists are very good at what they do in getting their message out,” argues Schwarz. And the scientists? “They’re not.”

The comments section is closed.

  • Sara says:

    I am really amazed that you do not look at the issue of impact of the GMP costs to farmers in human terms. The fact that seed cannot be saved and is very costly has had big impact on farmers and suicide in India. It is also about everything being set up for large corporations and not small farmers. There is a growing body of evidence that organically raised crops can provide the same amount of poroduce without the pesticides. But the real story is the loosing of diversity of types of crops and monocrops like bananas, when they fail, you loose the whole thing. I admit that bananas as a case is a grafted type of fruit but the failure is for all places around the world that grow banas for the North American and European markets.
    I think the issues of the freshness and the food value between organic and non- organic also suffers from how its measured and for what. However, there is no doubt that the beans, tomato, kale potatoes from my own garden to name a few of the veggies I grow has vastly superior taste and quality. And its difficult to believe that the length of time between commercial growers in new Zealand sending apples to Canada (as an example) can have as much food value as local foods.
    The use of pesticides and non-organic fertilizeer lead to poorer soil and poorer crops over time and this has been documented. And of course the impact on water quality from runoff to many creatures beyond humans.
    All of this has to be part of the mix of thought and not how the “coustomer propaganda” to make you feel good as an answer.

  • Chris Judd says:

    I would like to read the “entire scientific feeding trials” where feeding GMO feeds to animals showed NO difference in results! (remember that EVERY food fed to animals must be GMO and visa-versa for the animals fed the NON-GMO diet!)

  • Emmanuel Maicas says:

    I want to clarify that I do not denounce crop improvement. On the contrary, every mutation in crop plants, regardless of the technique used to obtain it, that is beneficial to humans should be celebrated as another victory of science over suffering. We cannot feed 10 billion humans without mutated plants. We need more science, not less.

    • Adeline Cohen B says:

      People have every right to attack science when it is used for short-term return and at the cost of sustainability and health (directly or indirectly). We need more science and we need strong scrutiny. While you are horrified by public distrust of GMOs, others are horrified by mad cow disease or dioxin chicken. Personally, I am terrified by superbugs and antibiotic resistance.

      I am also worried about your comment, Emmanuel, which sounds like you believe that genetic improvement will feed our growing population. The 2014 UN report on the Right to Food says that increasing yield alone will not work if it doesn’t take into consideration sustainable production and consumption.

      Very little is said about genetic improvement; the report calls for decreasing our demand for meat, limiting biofuel production expansion, reducing losses and waste along the supply chain and in people’s home (1/3 of the food we produce globally is wasted), and rebuilding local food systems (the Ontario Local Food Act of 2013 is given as positive example). So yes, science is needed: social science, behaviour science, political science as much as agricultural sciences.

      My point is that GMOs are dangerously overrated, and I would not waste any time education the public in defense of them, while the real challenge to work on is the right to food.

  • Emmanuel Maicas says:

    As a scientist, I am horrified by the negative discourse about one mutation technique, recombinant DNA, while all other mutation techniques used to genetically modify plant crops are absolved. Instead of asking for proof of the inocuity of Roundup-ready soyabean, we should ask for proof of the inocuity of all modern varieties of grape, apple, tomatoes, corn, wheat that all contain more sugar and less fibers than their ancestors.

    I will use the watermelon as an example. The images in the link below, courtesy of Syngenta, illustrate the striking man-controlled evolution of watermelon over more than a thousand years, from an apple-sized, white, hard, unsweet, seed-filled, autonomously reproducing fruit to a gigantic, red, extra-sweet, seedless monster that cannot reproduce ouside of a laboratory.

    These mutations are the result of “traditional” techniques. Thus, the resulting Frankenstein-like monster is not considered a GMO. When grown without pesticide, it may even be certified “organic”. What a joke!

    Like all modern fruit varieties, the fructose content of modern watermelons is much higher than that of their ancestor plant. Fructose is increasingly blamed for the ill-effects of excess sugar consumption. Where is the outcry against mutated watermelon? Where are the concerned “scientists” demanding the labeling of seedless, red watermelon with a health advisory? Where are the loonies in hazmat suits destroying fields of watermelons for the news cameras?

    What is happening to science, who are these people attacking it and why?

    • Graham Zaretsky says:

      Thank you for your intelligent and educational comment. I’m not a scientist. My degree is in Environmental Engineering, but I have not been working in that field. That said, I have been following the controversy for a while now. A few times when I’ve expressed the opinion that based on the evidence, GMO foods are not inherently dangerous, I’ve been accused of being a shill for Monsanto (I wish — I’m currently on disability and unable to work). It seems that in many circles, you cannot express skepticism without being seen as in league with ‘evil corporations’.

      What I want to ask, when someone claims that GMOs are ‘poison’ (which the last person to call me a schill claimed), is which specific food they are talking about, and what evidence they have that people have died or gotten sick because of that genetic modification. If a specific food, GMO or otherwise, is actually ‘poison’, then tell the FDA that THAT SPECIFIC FOOD should be taken off the market. I agree that no one should eat poison. Who could disagree with that? That the food is or is not a GMO is irrelevant, if you cannot prove that all methods of genetic modification result in poisoned foods. (I know that not all critics of GMOs make that claim — I just am tired of being called a Monsanto schill simply for believing the science).

      • Graham Zaretsky says:

        I also want to generalize what I said in the second paragraph to apply not just to accusations of health risks, but also to accusations of damaging the environment. Again, it’s stupid to spread such a narrow net when evaluating the environmental risks associated with crops. If the concern is environmental welfare, shouldn’t all agricultural methods come under scrutiny? It shows a kind of narrow-minded, prejudicial thinking. Even organic farmers have to deal with pests and weeds. I support efforts to reduce the use pesticides and herbicides, where such use has been shown to damage the environment or increase health risks. So let’s deal with that, and not get sidetracked by other issues. If and only if, you can show that ALL GMO foods are inherently more damaging to the environment by virtue of them being genetically modified, then logic should dictate that criticizing the use of a specific crop because it is a GMO has merit. Otherwise, again, deal with the specific danger. Don’t try to paint everything with the same brush.

    • Dylan McLernon says:

      As a scientist can you explain to me the long term effects of genetic modification, or the plausibility of genetic drift? Can you explain to me why Monsanto has created “terminator technology.” If they are concerned about the sustained health of people all over the world? Can you explain the sources talking about collusion among my Canadian government, the FDA and Monsanto? Can you explain why Canadian governmental scientists were fired or had their careers absolutely destroyed for not excepting rbGH from Monsanto without further studies? As a scientist you ought to be ashamed of your field. Science is becoming the new bible and you are all pretending to be the new god.

      One would think after Clair Patterson and the leaded gasoline debacle people would have been enough. Then there was DDT and agent orange, all of which are still creating adverse effects on our ecology. Yet here we are, you defending horizontal gene splicing, and crying about the vertically branched movement of breeding. It all comes back to eugenics, which I thought we were also rid of after WWII.

  • Adeline Cohen B says:

    Thank you for this interesting read. I agree that the disconnect between evidence and public opinion is very real. The GMO debate can be taken under so many angles that I have yet to see an article that speaks to all aspects of the GMO problem.

    To me, there are two issues with GMO: the irreversible character of environmental pollution that GMO generate and the control that biotechnology firms have over farmers around the world through the patenting of seeds. These two issues have been expressed from the start of the GMO debate, but I rarely see them expressed in public debates. Maybe because it is hard to relate for the general public, the non-GMO movement is using health and safety as a way to reach the public.

    As an agricultural engineer, I have followed the debate for many years. %featured%My main concern is that GMO research is very costly and takes the biggest share of agricultural research funding, while it is unlikely to deliver soon on the key promises put forward, such as crop that yield more grain while using less water. %featured%I have discussed this in my latest blog post

    Also, I am curious to know if you have come across any research on the potential impact of GMO on the intestinal microbiota.

    • Emmanuel Maicas says:

      Adeline, before you ask what effect a non-browning apple will have on the gut microbiota, ask yourself what impact do modern “natural”, “traditional” cultivated plants have on human health.

      As an agricultura engineer, you are surely aware that modern wheat is the result of crosses between several wild diploid grasses, some yet unknown, resulting in tetraploid or hexaploid monsters. Wheat is truly Frankenstein food. During this artificial evolution driven by humans over millenia, the starch and gluten content was increased, the bran and oil content was decreased. The daily consumption of large amount of this artificial plant has been blamed for the increased incidence of several serious maladies, including celiac disease, obesity, diabetes and colon cancer. Read Dr William Davis’ book for a summary of the evidence.

      Similar stories can be told about all modern varieties of cereals, fruits and vegetables that, over centuries, have been selected for higher sugar and lower fiber contents. None of these modifications required recombinant DNA technique. They were the result of old-fashioned, natural gene-modification techniques like colchicine (a violent poison with no known antidote) and radioactivity from Radium or Plutonium (the stuff in atomic bombs). Less like Frankenstein, more like Spiderman.

      Ironically, when these grossly mutated, diformed, barely recognizable plants are grown without pesticide, they are called “organic”.

      In sum, the well-documented dangers resulting from “traditional” crop plant mutations greatly exceed the hypothetical dangers from recombinant DNA technology.

      • William says:

        One point to pick with you – “Ironically, when these grossly mutated, deformed, barely recognizable plants are grown without pesticide, they are called “organic”.”
        99.99% of pesticides in the environment reside in the plants themselves and are wholly “natural”. Also, organic farmers do use pesticides – so-called natural ones, often being more “toxic” than synthetic ones.

  • Dontaylor says:

    A succinct summary of the issue. Thank you.

  • Wayne says:

    Never let the truth get in the way of a good story.


Wendy Glauser


Wendy is a freelance health and science journalist and a former staff reporter with Healthy Debate.

Timothy Caulfield


Timothy Caulfield is an author and Canada Research Chair in Health Law and Policy, University of Alberta.

Debra Bournes


Dr. Debra Bournes is the Chief Nursing Executive and Vice-President of Clinical Programs at The Ottawa Hospital.

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