#437: GMOs & Genetic Engineering: Harmless or Health-Hazard?

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Table of Contents

  1. Introduction
  2. Hosts
  3. Overview (with timestamps)
  4. Related Resources
  5. Key Ideas (Premium Subscribers Only)
  6. Detailed Study Notes (Premium Subscribers Only)
  7. Transcript (Premium Subscribers Only)


The issue of genetic enginnering in the food system is one that is often charged with emotion and strong opinion. Indeed, there has been much concern voiced over the years about the potential harms to both human health and the environment of genetically-modified (or more accurately, genetically-engineered) crops.

Some concern takes the form of outright hysteria, while other concerns are more nuanced and subtle. Among these concerns, which have good evidence to support them? What regulation is currently in place? Why are their differences between the US and the EU?

On the opposite side, there are clear advantages to GE crops; including disease resistance, herbicide tolerance, and even enhanced nutritional content. But are these advantages possible without harm? Do the pros outweigh the cons?

In this episode, Alan and Danny discuss the current evidence on genetically engineered crops (or GMOs) and their effect on human health, biodiversity, and the economy.



Public Feed Timestamps:

  • 02:02 – Framing of the GMOs debate
  • 13:52 – Key definitions
  • 20:34 – Where do GMOs show up in the food supply? And jurisdiction differences
  • 33:40 – Impacts on human health and nutritional differences
  • 45:16 – Impact on biodiversity
  • 1:01:57 – What’s the deal with glyphosate herbicide?
  • 1:05:34 – Concluding thoughts

Premium Feed Timestamps:

  • 00:57 – Framing of the GMOs debate
  • 12:47 – Key definitions
  • 19:29 – Where do GMOs show up in the food supply? And jurisdiction differences
  • 32:35 – Impacts on human health and nutritional differences
  • 44:11 – Impact on biodiversity
  • 1:00:52 – What’s the deal with glyphosate herbicide?
  • 1:04:29 – Concluding thoughts
  • 1:09:42 – Key Ideas segment (Premium only)

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  1. Detailed Study Notes
  2. Transcript

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Key Ideas

Key Idea #1

When people refer to GMOs they are usually referring to crops developed through genetic engineering. Genetic Engineering is the name for certain methods used to introduce new traits or characteristics to an organism typically involving the use of recombinant DNA methods. While these techniques are sometimes referred to as “genetic modification”, it is “genetic engineering” that is the more precise term for what is typically discussed.

Key Idea #2

While it’s clear that most claims highlighted the dangers of GMOs/GE crops are hyperbolic and lacking in evidence, this is not to say that:

  • There is no chance of any risks ever being found
  • The food industry players are always honesty, ethical actors
  • The food system doesn’t need reform
Key Idea #3
  • Anti-scientific thinking often is borne out of a craving more certainty.
  • People who attempt to get rid of the uneasy feeling of uncertainty, attempt to create certainty by claiming something is definitely dangerous or incredibly beneficial.
  • We must be comfortable with saying, we can’t know for sure, but based on current best evidence, and what is likely to be correct, our current position is X.
  • There needs to be an ability to sit with ambivalence and make probabilistic decisions.

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Detailed Study Notes


  • Biotechnology: The broad umbrella term for the set of tools that uses living organisms (or parts of organisms) to make or modify an organism for specific uses. Examples: fermentation (chees, wine, beer), making culture cells for research, techniques used in the process of making genetically modified crops
  • Genetic Engineering: The name for certain methods used to introduce new traits or characteristics to an organism typically involving the use of recombinant DNA methods. While these techniques are sometimes referred to as “genetic modification”, it is “genetic engineering” that is the more precise term for what is typically discussed.
  • Genetically Modified Organism (GMO): Often used to describe organisms developed using the tools of genetic engineering. The terms GMO crop and GE crop will be used interchangeably in these notes.
  • Mutagenesis: A process by which an organism is genetically changed, resulting in a mutation. It may occur naturally, for example, due to natural exposure to ultraviolet (UV) light or chemicals; or it can happen deliberately for the purpose of increasing genetic variation of a species.
  • Transgenic Organism: Organisms that have had genes from other species inserted into their genome.

What’s the Issue?

This can be a topic that is often high on emotion and activism, yet low on good faith scientific discourse. And often there is a disconnect between scientific evidence and the beliefs of those who are most concereded about GMOs.

An example of this disconnect can be seen in some Pew surveys in the US in recent years:

In a 2015 survey, Pew Research Center surveyed both citizens and a representative sample of scientists connected to the American Association for the Advancement of Science (AAAS):

  • 88% of scientists surveyed reported they felt GMOs were safe.
  • 37% of the general population did.
  • This represents a 51 point gap in opinion.

Then another Pew survey from 2016 showed a similar disconnect:

  • A nationally representative survey of 1,480 adults.
  • 39% thought GM foods are worse for health than non-GM foods
  • When looking to seem what other aspects were associated with one’s position on GMOs, Pew tied someone’s conclusions about health effects to how deeply they care about the issue.
    • Only a minority of those surveyed state that they “care deeply” about the issue of GM foods (16%). But these people are much more likely to consider GM foods worse for health, than those with less concern about this issue.
      • 75% of those who “care deeply” see GMOs as harmful
      • 17% of those who don’t “care deeply” see GMOs as harmful
  • It also seems to more likely that those who are more skeptical of industry influence on science will see GMOs as harmful:
    • “… people with a deep concern about the issue of GM foods are particularly skeptical of information from food industry leaders about the health effects of GM foods and see more industry influence on science research findings than do other Americans.”
  • When those surveyed were asked how many scientists believed GMOs are safe, 53% of respondants stated they felt that half or fewer of scientists believed GMOs are safe. (Compare this to the 88% of scientists reporting they felt they were safe in the 2015 survery).

This distrust of GMOs in the general population is also prevalent in Europe, with a 2010 report by the European Commission reporting that:

  • 61% of EU disagree that “GM food is safe”
  • Less than a third believes that “GM Food is good for the economy”

This public distrust or concern is somethign that has been noted and summarised well by a 2012 report by the AAAS: “There are several current efforts to require labelling of foods containing products derived from genetically modified crop plants, commonly known as GM crops or GMOs. These efforts are not driven by evidence that GM foods are actually dangerous. Indeed, the science is quite clear: crop improvement by the modern molecular techniques of biotechnology is safe. Rather, these initiatives are driven by a variety of factors, ranging from the persistent perception that such foods are somehow “unnatural” and potentially dangerous to the desire to gain competitive advantage by legislating attachment of a label meant to alarm. Another misconception used as a rationale for labelling is that GM crops are untested.”

What are GMO Foods? What is Genetic Engineering?

When people refer to GMOs they are usually referring to crops developed through genetic engineering.

Genetic Engineering: The name for certain methods used to introduce new traits or characteristics to an organism typically involving the use of recombinant DNA methods. While these techniques are sometimes referred to as “genetic modification”, it is “genetic engineering” that is the more precise term for what is typically discussed.

Genetic engineering allows plant breeders to take a desirable trait found in nature and transfer it from one plant or organism to the plant they want to improve, as well as make a change to an existing trait in a plant they are developing.

Examples of desirable traits:

  1. Disease resistance – e.g. GM Rainbow Papaya resists the papaya ringspot virus
  2. Herbicide tolerance – with the goal to weed control easier, cheaper and more effective
  3. Insect resistance – e.g. the use of Bt Corn to combat the European corn borer
  4. Enhanced nutritional content – e.g. Golden Rice is a rice biofortified with vitamin A (more on this later).
  5. Drought tolerance – Can make crops better able to cope in drought conditions, although not that much larger yields tend to be seen
  6. Reduced food waste – e.g. via gene editing, there is a non-browning Arctic apple, which prevents apples being thrown out before consumption
Genetic Modification

Genetic modication is a much broader term that includes many forms of modifying plants and other organisms. Genetic engineering (and GMO crops) and just a small subset.

So there are other forms of genetic modification:

  1. Traditional Crossbreeding
    • e.g. Honeycrisp apples
  2. Mutagenesis
    • e.g. Deepens the red colour of the flesh of certain grapefruit varieties
  3. Gene Editing
    • e.g. low-gluten wheat created via CRISPR-Cas9
Infographic from: gmoanswers.com

Gene editing – From episode 120 of the podcast with Dr. Kevin Folta: “The other example is where you take something out, and that’s a good example of this White Russet potato that’s coming out and also this non-browning Arctic apple. Here a gene that’s responsible for causing the oxidative browning that apples and potatoes experience, the gene has been silenced.”

Mutagenesis – researchers force the mutation of a plant’s genetics, for example, by exposing seeds to chemicals or irradiation to induce changes in their DNA. These crops are not considered GMOs and this technique is not considered genetic engineering.

Where do we find them? What foods are GE?

The Agricultural Marketing Service (AMS) developed the List of Bioengineered Foods to identify the crops or foods that are available in a bioengineered form throughout the world. The list currently includes:

  • Alfalfa
  • Apple (Arctic varieties)
  • Canola
  • Corn
  • Cotton
  • Eggplant (BARI Bt Begun varieties)
  • Papaya (ringspot virus-resistant varieties)
  • Pineapple (pink flesh varieties)
  • Potato
  • Salmon (AquAdvantage®)
  • Soybean
  • Squash (summer)
  • Sugarbeet

As of 2022, it is now mandatory in the US for a “bioengineered” label to appear on foods, due to the National Bioengineered Food Disclosure Standard.

Image from: ISAAA, 2019
Cultivation Authorisation vs. Food & Feed Use Authorisation

Countries and regions can authorise the GE crops to be cultivated and/or used for feed or human food.

In the EU, currently there is only one GE crop authorized to be commercially cultivated; GE maize/corn (MON 810), which is resistant to the actions of the European corn borer. According to the European Commission, there are 8 pending applications for GMO cultivation in the EU, including renewal of MON810 authorisation. 4 have had a positive EFSA opinion; 4 are awaiting an EFSA opinion.

B comparison, as of April 2022, 58 GMOs are authorised in the EU for food and feed uses (covering maize, cotton, soybean, oilseed rape, sugar beet). 58 application files are pending, out of which 17 have a positive EFSA opinion and 1 has an inconclusive opinion.

Example: GE Soybean Use in the EU

  • All Member States have important livestock production
  • All EU member states import or use soymeal
    • Soymeal is the main source of proteins for animals feeding
  • EU highly dependent on outside countries for soymeal:
    • In 2013 96% of EU Consumption was from imported soybean and soymeal
    • Almost 90% of imported soymeal is GM.
    • GM soy is not cultivated in the EU.
Image from: European Commission presentation on GMO’s, Brussels, 2015

The list of authorised GM plants and the precise scope of their authorisation is available in the EU register of GM food and feed.

Animal Products & GMOs

Eating animal products from animals fed GMOs

  • More than 95% of animals used for meat and dairy in the United States eat GMO crops.
  • Foods like eggs, dairy products, and meat that come from animals that eat GMO food are equal in nutritional value, safety, and quality to foods made from animals that eat only non-GMO food.
  • Intact or immunologically reactive protein or DNA has not been detected in animal tissue.

Are there GE animals in the food system?

  • FDA has approved an application that allows the marketing of the AquAdvantage Salmon, an Atlantic salmon that has been genetically modified to reach an important growth point faster.
  • FDA determined that AquAdvantage Salmon is as safe to eat and as nutritious as non-GMO Atlantic salmon.
  • FDA also found that its approval of the application for this salmon would not significantly impact the U.S. environment.
  • Article: First Genetically Engineered Salmon Sold in Canada
  • In a recurring theme, the EU has a much more cautious approach than that in North America, and currently seems to be in a “wait-and-see” position with regard to transgenic salmon.

Policy Approaches: US vs. EU

“The EU ‘precautionary principle’ means genetically modified foods, for example, have been tightly regulated until such time as they can be proved not to be harmful to humans or the environment. By comparison the US operates the other way around – innovations are permitted until they are proven to be harmful.” – Caroline Bovey, Chair of the British Dietetic Association

European Commission: “The approach chosen in the EU as regards GMOs is a precautionary approach imposing a pre-market authorisation for any GMO to be placed on the market and a post-market environmental monitoring for any authorised GMO. This approach ensures a high level of protection of human and animal health and the environment.”

The European Food Safety Authority (EFSA), in collaboration with Member States’ scientific bodies, is responsible for the risk assessment which needs to demonstrate that, under its intended conditions of use, the product is safe for human and animal health and the environment.

GMOs & Human Health

Data from animal feeding studies provides a layer of evidence about the effects of conusming GMO grops. In a literature review of animal feeding trials by Snell et al. (2012), the authors concluded:

“Results from all the 24 studies do not suggest any health hazards and, in general, there were no statistically significant differences within parameters observed. However, some small differences were observed, though these fell within the normal variation range of the considered parameter and thus had no biological or toxicological significance. If required, a 90-day feeding study performed in rodents, according to the OECD Test Guideline, is generally considered sufficient in order to evaluate the health effects of GM feed. The studies reviewed present evidence to show that GM plants are nutritionally equivalent to their non-GM counterparts and can be safely used in food and feed.”

“The committee also examined epidemiological data on incidence of cancers and other human-health problems over time and found no substantiated evidence that foods from GE crops were less safe than foods from non-GE crops.” – National Academy of Sciences – expert report

Keshani et al., 2020: “Our findings indicated that GM products had no adverse effects on infertility indices such as the sperm head, sperm motility, sperm abnormality, and fertility indices.”

Is there a nutritional difference between GMO and non-GMO foods?

GMO/GE foods do not seem to be inferior nutritionally compared to non-GE foods. For example, Jiao et al. (2010) showed that the nutrient composition of GE and non-GE papaya was the same.

Where there are differences in nutrient composition, it is intentional! i.e. when that is the goal. Examples include biofortified crops such as high-oleic soybeans or Golden Rice (rice biofortified with vitamin A).

  • Biofortification increases the nutritional value of crops through either selective breeding or genetic modification
  • Biofortified crops are not commercially available to the public yet
  • An example of the potential for biofortified crops is that of Golden Rice – rice biofortified with vitamin A.
    • There is a major vitamin A deficiency prevalence in developing world.
    • Vitamin A deficiency can lead to irreversible childhood blindness.
    • By have Golden Rice in populations where rice is a staple part of the diet and where vitamin A deficiency is rampant, there could be a massive reduction in this preventable condition.
  • A biofortified crop that has been approved by the FDA is the Pink Pineapple.
    • Pink Pineapples are GMO crops fortified to contain higher levels of lycopene.
    • Lycopene is a carotenoid, with antioxidant capacity.
    • It is currently available in North America, sold commercially as Pinkglow pineapples from Del Monte.

The roll-out of bioengineered crops such as Golden Rice, continues to be held up due to concerns about GE crops. This is despite many calls for their immediate adoption. Wu et al., in a 2021 piece in PNAS, called for Golden Rice to be rolled out and cited the pushback as anti-scientific, stating:

“The arguments used by organizations to delay adoption of GR often resemble the arguments of anti-vaccination groups, including those protesting vaccines to protect against COVID-19. Some of the opponents of GR and agricultural biotechnology more generally see the introduction of GR as forcing the consumption of GMOs on the population. However, for the case of GR, consumers have the option of easily avoiding consumption because GR is very easily identifiable by its color. The tragedy of GR is that regulatory delays of approval have immense costs in terms of preventable deaths, with no apparent benefit.”


Evaluating GMO products for allergic potential is a requirement for new GMO crops: The European Food Safety Authority has 2017 document titled “Guidance on allergenicity assessment of genetically modified plants” that provides a detailed explanation on how allergenicity is to be assessed.

A systematic review by Dunn et al. (2017) reported:

  • “… GM products do not appear more allergenic than their conventional counterparts as determined by IgE binding studies in well-characterized sera from humans with allergy and animal models, case series of direct provocation and ingestion, and simulated digestion studies. These are methods approved by the World Health Organization for determining allergenicity of GM products.”
  • “… there is no evidence that eating GM products in individuals who are not allergic to conventional forms of those items would result in allergy or increase the risk of developing an allergy to that item.”
  • “… GM foods do not appear to be more allergenic than their conventional counterparts, and no data exist that consumption of GM proteins causes allergy to develop to that particular food in individuals who are not allergic at baseline.”

Environmental Issues

There have been some arguments put forward suggesting possible detrimenal impacts on biodiversity and insect populations.

  • However, the main arguments don’t necessarily state GMOs are the direct problem per se, but rather than their use can bolster an already problematic (and unsustainable) industrial system of farming, that is present in many places.
  • Whether they lead to loss of biodiversity may be hard to quantify. As per Johnson et al., 2010: “On the other hand, the switch to GE crops with herbicide resistance has eliminated many blooming plants from field borders and irrigation ditches as well as from the crop fields themselves. The reduction in floral diversity and abundance that has occurred due to the application of Round-UP® Herbicide (glyphosate) to GE crops with herbicide resistance is difficult to quantify.”

On the issue of biodiversity, there are then arguments put forth on the other side; i.e. suggesting either no harm or even potential benefit:

  • Meta-analysis by Klumper & Qaim, 2014: Potential fewer pesticide applications, conservation tillage (which reduces greenhouse gas emissions), and water conservation are all practices that can be used with GE crops.
  • By sparing land that is not intensively cultivated, GE crops could increase productivity on existing agricultural land and therefore protect biodiversity. Highlighted in Raven, 2010 review:
    • “… we note that the ecological problems related to the cultivation of GE crops fail to differ in any fundamental way from the ecological problems associated with agriculture in general, except that they usually involve the application of much lower quantities of chemicals and thus tend to leave the environments in and adjacent to where they are grown in better condition than do the conventional ones.”
    • “Higher productivity on cultivated lands, which is one outcome of growing GE crops, protects biodiversity by sparing lands not intensively cultivated, whereas relatively non-productive agriculture practised is highly destructive to biodiversity, since it consumes more land in an often destructive way, even though more biodiversity may be preserved among the crops themselves than in industrialized, large fields, especially if hedgerows and woodlands are not encouraged in near proximity”
  • Also there are certain GE-crops (e.g. certain corn varieties) that improve the process by which cellulose/starch is broken down and converted to fuel, i.e. they cna allow a more efficient production of biofuel. As this can decrease the amount of water and gas used in the process, this could reduce the environement impact.

“The NAS committee found that the introduction of Bt varieties (which incorporate a natural pesticide) reduced overall pesticide use, reduced pest populations (and therefore benefited even non-GMO crops), and increased insect diversity. Likewise, the use of herbicide-resistant crops has resulted in a small increase in yield without any decrease in plant diversity.”- National Academy of Sciences – expert report

Do GE-crops negatively impact insect populations?
  • It is a plausible hypothesis that they could harm bee populations, given the potential to induce a stress or low-grade poisoning (from the increased herbicide for example).
  • However, evidence seems to suggest they don’t harm bees:
    • Duan et al., 2008 meta-analysis of 25 studies
    • Johnson et al., 2010 discuss the potential for benefit even: “There is no evidence that the switch to Bt crops has injured honey bee colonies in the USA. To the contrary, it has benefited beekeeping by reducing the frequency of pesticide applications on crops protected by Bt, especially corn and cotton.”

There was also worry about the impact on butterfly populations, following a 2017 report by the Center for Biological Diversity, stating: “The butterfly’s dramatic decline has been driven in large part by the widespread planting of genetically engineered crops,” “The dramatic surge in the use of Roundup and other herbicides … has virtually wiped out milkweed plants in the Midwest’s corn and soybean fields.”

However, a more recent analysis by Boyle et al., 2019 strongly disagreed with such claims, stating:

“The recent decline of the monarch butterfly has attracted a great deal of attention. One of the leading hypotheses blames genetically modified (GM) crops, ostensibly because of the impact of GM-related herbicide use on the monarch’s food plants, milkweeds. Here, we use museum specimen records to chart monarch and milkweed occurrence over the past century (1900 to 2016), dating well before previous datasets begin (in 1993). We show that monarch and milkweed declines begin around 1950 and continue until the present day. Whatever factors caused milkweed and monarch declines prior to the introduction of GM crops may still be at play, and, hence, laying the blame so heavily on GM crops is neither parsimonious nor well supported by data.”

Ethical Issues

The Academy of Nutrition and Dietetics (AND) set out a code of ethics for nutrition & dietetics professsionals, defining this as “a set of standards that govern or influence the conduct of behavior of a food/nutrition professional or organization and can be influenced by food customs and societal customs.”

As Dizon et al. (2016) highlight, based on the principle of ‘autonomy’, “the consumer has a right to know what they are purchasing to make informed decisions.”

This naturally brings up the issue of labelling. As noted above, as of 2022 it is mandatory in the US for a “bioengineered” label to appear on foods, due to the National Bioengineered Food Disclosure Standard.

However, whether labelling will impact consumer behaviour is debatable. A cool recent two-phase RCT by Oselinsky et al. (2021) examined how GMO-labelling impacts choices among college students (the age group which values transparent food labeling more than any other). They found:

  • 85% of participants reported believing that GMOs were at least “somewhat dangerous” to health
    • 42% believed GMOs to be “dangerous”
  • Eye-tracking data verified that participants did pay attention to the GMO labels.
  • However in both studies, these labels did not significantly affect food choices.

In relation to impact on farmers, there seems to be an overall positive economic impact:

  • Zilberman et al., 2010: “Overall, GE crops seem to improve farm profitability while also reducing commodity prices to the benefit of consumers.”
  • National Academy of Sciences – expert report: “The available evidence indicates that GE soybean, cotton, and maize have generally had favorable economic outcomes for producers who have adopted these crops, but outcomes have been heterogeneous depending on pest abundance, farming practices, and agricultural infrastructure.”

Similarly, the impact on livestock does not seem to be additionally detrimental:

“The design and analysis of many animal-feeding studies were not optimal, but the large number of experimental studies provided reasonable evidence that animals were not harmed by eating food derived from GE crops. Additionally, long-term data on livestock health before and after the introduction of GE crops showed no adverse effects associated with GE crops.” – National Academy of Sciences – expert report


  1. Based on current evidence, there doesn’t seem to be any harm to human health when eating GE crops compared to eating non-GE crops.
  2. There regulation and safety evaluation differs significantly by region, with an almost polar opposite approach taken in the EU vs. in the US.
  3. Concerns about environmental impacts have been put forward, but in general these seem to relate to the fact that GE crops can potentially bolster an already problematic food system/industrial farming system, rather than being due to genetic engineering per se.
  4. While it’s clear that most claims highlighted the dangers of GMOs/GE crops are hyperbolic and lacking in evidence, this is not to say that:
    • There is no chance of any risks ever being found
    • The food industry players are always honesty, ethical actors
    • The food system doesn’t need reform

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