Are GMOs safe?
A health-conscious scientist's perspective on GMOs
As a kale-loving health nut with a PhD in genetics, I am often asked for my opinion on GMOs.
My answer often surprises people. I pay no attention to whether or not a product is GMO - made with genetically modified organisms. I am very confident that our food supply is safe (both GMO and non-GMO foods) based on a robust body of scientific evidence. In fact, I dislike the non-GMO label because it is often misleading and fuels false fears towards safe foods.
Today, I want to share some of the research that informed my take on GMOs and dispel some common myths about the link between GMOs, pesticides, and health.
What is a GMO?
A GMO (genetically modified organism) is a plant, animal, or microbe whose genetic code (DNA) has been altered using genetic engineering to permanently modify the organism in a desired way (e.g., to fight pests). In agriculture, genetic engineering offers a faster, more precise, and more flexible way to alter DNA than traditional breeding and is known as “precision agriculture”. Beyond agriculture, GMOs are also used to make medicines, vaccines, vitamins, textiles, and more. GMOs are also known as GM (genetically modified) or GE (genetically engineered) crops.
Note: Plant-based GMOs are often referred to as GM (genetically modified) or GE (genetically engineered) crops.
Before we explore the safety of GMOs, I want to clear up some confusion about where GMOs show up in our food system and when the GMO label is (and is not) informative.
Which foods are genetically modified?
The vast majority of GM (genetically modified) crops are not sold directly to consumers: they are used to feed animals and make ingredients for processed foods (US FDA). When shopping for animal products or packaged foods, a non-GMO label tells you something about the source of the ingredients - but not about health or safety (we’ll explore the data shortly).
When shopping for produce, a non-GMO label is virtually irrelevant. Almost all fresh (and frozen) fruits and veggies are non-GMO, whether or not they have this label. There are no available GMO versions of berries, salad greens, peas, carrots, bananas, oranges, pears…. and more. The only fresh fruits and veggies sold with a GMO version on the market are: rainbow papaya (virus resistant), Innate Russet Potato (non-browning/bruising), Arctic apples (non-browning), pink pineapple, and certain summer squashes (US FDA).
Image adapted from FDA
Are GMO foods safe?
There is a strong scientific consensus that genetically engineered crops (GMOs) are safe. This conclusion is supported by dozens of independent health and safety organizations worldwide and a vast, compelling body of scientific evidence.
Many health and safety organizations have reviewed the health and safety of GMO foods, including: the National Academy of Sciences in the US, the Royal Society in the UK, the European Food Safety Authority, the Australian Academy of Science, the World Health Organization, and many more. These organizations have reached the same conclusion: GM crops are no riskier than conventional crops.
The massive body of evidence on GMO health and safety spans decades of research and includes hundreds of studies in plants, animals, and humans. These studies have evaluated a wide range of potential concerns about GMO safety (e.g.,allergic reactions, organ damage, or gene transfer from GMOs to our gut microbes) and found that they are not supported by current evidence. The handful of “alarming” GM studies lurking online are not credible - they have seriously flawed methods and come from a small group of labs (red flag!). Not every scientific study deserves to be taken seriously.
Going forward, we can be confident that any new GMOs that enter the food supply are well-tested and safe, thanks to stringent regulatory oversight. In fact, GMO crops are more tightly regulated than their non-GMO counterparts. For example, new GMO foods are rigorously evaluated for allergic potential before being approved, and the use of common allergens is avoided (like nuts, soy, seafood, eggs, wheat, and dairy). This regulatory process has been highly successful - there is no evidence of a GMO-related allergic reaction (you are either allergic to soy or not; GMO status is irrelevant).
Nerd Note: There is DNA in all the plants, animals, and microbes that enter our bodies in every bite, GMO or not. This DNA is simply broken down and does not impact our health (nor our DNA). There is nothing dangerous about eating something that contains “foreign” DNA.
GMOs and pesticides
The link between GMOs, pesticides, and health is widely misunderstood. Let’s tackle some common myths:
Myth 1: Pesticides are only present in GMO foods.
Reality: Pesticides are used by the vast majority of farmers, even small-scale and organic farmers (who are permitted to use non-synthetic pesticides- many of which are highly toxic). A non-GMO label does not mean pesticide-free (neither does an organic label!)..
Myth 2: GMOs are driving up pesticide use.
Reality: The use of genetic engineering has definitely changed pesticide practices - but the effect is not all bad. Farmers growing herbicide tolerant crops (eg. Roundup Ready corn) typically use more glyphosate, a broad-spectrum weedkiller, but less of other pesticides than they would otherwise. Farmers growing insect-resistant crops (e.g. Bt corn) typically use far fewer pesticides than those growing conventional crops. A study of pesticide use from 1996 to 2020 found that the total pesticide burden (amount of active ingredient) was roughly the same (or lower) between GMO and non-GMO crops.
Myth 3: The pesticide levels in our food supply are worrisome (due to GMOs).
Reality: Pesticide levels are routinely assessed in thousands of foods, with reassuring results in both GMO and non-GMO foods. The US Pesticide Monitoring Program and Health Canada consistently finds that over 99% of foods are well below the safe limit for pesticide residues. A recent report by Europe’s Food Safety Authority found that 96-98% of foods were within the safety limits for pesticides.
Myth 4: Detectable levels of glyphosate in our urine are cause for alarm.
Reality: Detectable is not the same as harmful. There are plenty of toxic chemicals inside our bodies (including natural substances like formaldehyde) that don’t harm us because the exposure level (dose) is so low.
Whenever we’re thinking about the link between a chemical and health, we must bear in mind the central tenet of toxicology: the dose makes the poison. The safety of everything we are exposed to is inextricably linked to dose - whether that substance is a medication like Tylenol, an environmental exposure like pollution, or a pesticide. There is always a threshold above which the harms set in and below which we are safe.
Glyphosate is the world’s most widely used pesticide (herbicide), so it’s no surprise that it’s sometimes detectable in our bodies. Farmers use it to fight weeds when growing some GMO crops (Roundup ready corn, soy, canola, cotton) as well as many non-GMO crops (fruits and veggies). Several studies have shown that small amounts of glyphosate can be detected in our urine. This sounds scary, but it’s not cause for alarm unless you know how our exposure compares to the safe limits. When we do this, the picture is not so scary: multiple studies have shown that glyphosate exposure levels in North America and Europe are well below the safe limits.
Unfortunately, many studies report urinary pesticide levels as if any non-zero level is cause for alarm. For example, a French study measured glyphosate levels and emphasized “widespread contamination” without putting the results in context. A scientific critique of this study calculated that the glyphosate exposures in this “concerning” study are 25x below the safe limits (4% of the safe limit). -
It makes sense to be mindful of pesticides, but please keep this risk in perspective! According to a 2018 risk-assessment study, the hazard index (health harm) for pesticides for a Danish adult was on par with consuming the equivalent of 1 glass of wine every seven years. This piece by our fellow nerds at SciMoms and collaborators called “Zero Risk is an Impossible Dream,” nicely illustrates the risk landscape.
Image Credit: SciMoms and CargoCollective and Thoughtscapism.
As you can see from the figure, the health risks of pesticides are not zero, but they are “in the weeds” (pun intended!).
Beyond health
The environmental, economic, and social consequences of GMOs are complex, and a full discussion of this topic is beyond the scope of this article, and beyond my expertise. However, I have done some digging into this topic and have a good sense of the major themes. The most important thing I’ve learned is that GMOs are not uniformly bad or good for the environment or for farmers. The impacts depend on the GMO, the metric (e.g., pesticide use, biodiversity, farmer profit), the context (e.g economic and policy environment). Even the same GMO can have a mix of positive and negative impacts (e.g., producing higher farmer profits while generating more resistant weeds).
The bottom line
There is a clear scientific consensus that GMO foods are safe and are not causing dangerous levels of pesticides in our food. A non-GMO label is not an indicator of “healthiness” and is virtually meaningless when shopping for whole fruits and veggies, since GMOs are largely used to feed animals and make ingredients for processed foods.
As you learn more about GMOs, be careful where you get your information. Be leery of anyone who paints all GMOs with the same brush and look out for biased sources like organic lobbies, which incite fear by suggesting that we should worry about unknown risks. For example, the non-GMO project website states: “In the absence of credible, independent, long-term feeding studies, the safety of GMOs is unknown” - a blatantly false statement that ignores the scientific consensus and robust body of evidence.
Below, I have provided a number of science-based sources that delve into the health, safety, environmental and social consequences of GMOs. If you enjoy podcasts, check out my chat with Dr. Anastasia Bodnar, a science policy advisor with a PhD in genetics with a minor in sustainable agriculture, who co-founded SciMoms and Biology Fortified.
Thanks for making it all the way to the end of this lengthy post! This was a doozy of a topic, and I learned a lot along the way. Given the public controversy and misunderstandings about GMOs, I expect that this article will raise questions for some of you. I welcome any feedback that stems from genuine curiosity and knowledge-seeking and will use it to inform future posts.
Yours in science and in health,
References and resources
Introduction to GMOs | SciMoms
Signal to Noise Special Edition: GMOs and Our Food - Science in the News | Harvard
Genetically Modified Foods | World Health Organization
Genetically modified (GM) plants: questions and answers | Royal Society