Scientists Say GMO Foods Are Safe, Public Skepticism Remains

Genetically-engineered crops are as safe to eat as their non-GE counterparts, they have no adverse environmental impacts, and they have reduced the use of pesticides. That’s according to a comprehensive report released by the National Academy of Sciences today—a group founded by the U.S. Congress to provide expert scientifically-based advice on a wide variety of issues.

But the academy also found that GE or (genetically-modified organisms or GMO) crops didn’t increase those crops’ potential yields, and they did lead to widespread and expensive problems with herbicide-resistant weeds.

The report acknowledges that beyond safety, other issues need to be addressed, including earning the public’s trust. It recommends a more transparent and inclusive conversation about GE crops going forward.

The report, two years in the making, is a 388-page, comprehensive look at every aspect of genetically engineered crops. “Sweeping statements about GE crops are problematic because issues related to them are multidimensional,” the report says right up front, and goes on to dig deep on those dimensions.

170.3 million hectares have been planted with genetically-engineered crops, as shown on this map. Courtesy National Academy of Sciences

170.3 million hectares have been planted with genetically-engineered crops, as shown on this map. Courtesy National Academy of Sciences

The assessment is generally positive, but there are many caveats and notes of caution. For those of you who want just the big takeaways, here’s the nutshell version:

  • GE crops are safe to eat.  There is always uncertainty about safety, of course, but there’s no evidence of harm.
  • The GE crops in our food system don’t improve on the crops’ potential yields. They have, however, helped farmer protect yields from insects and weeds.
  • Both herbicide-tolerant crops and crops with the organic pesticide Bt built in have decreased pesticide use, although those decreases came early on, and some have not been sustained.
  • Increased use of glyphosate, the herbicide GE crops tolerate, has been responsible for a widespread and expensive problem of glyphosate-resistant weeds.
  • The report found no adverse affects on biodiversity or danger from interbreeding between GE crops and wild relatives.
  • Although both the use of GE crops and the employment of farming techniques that reduce tilling have been on the rise, the report finds no cause-and-effect relationship.
  • The economic benefits to farmers have been well-documented, although individual results vary.
  • Small-scale farmers may have trouble seeing those economic gains because of the price of seed and lack of access to credit.
  • Appropriate regulation is imperative, and that regulation should be based on the characteristics of the crop, rather than the technique used to develop it, whether GE or non-GE.
  • Ongoing public conversations about GE crops and related issues should be characterized by transparency and public participation.

The report also notes that both genetic engineering and conventional breeding are important to crop improvement. Each method has strengths and weaknesses, and treating them “as competing approaches is a false dichotomy; more progress in crop improvement can be brought about by using both … than by using either alone.” (See Can This Scientist Unite Genetic Engineers and Organic Farmers?)

For those of you who interested in chapter and verse of the report, here is soup-to-nuts rundown of the committee’s findings:

Human Health

The committee doesn’t find evidence the consumption of the GE foods currently in our food supply increase food allergies, have significant effects on the GI tract, or pose a risk for horizontal gene transfer.

Photograph by Becky Harlan

Photograph by Becky Harlan

It also doesn’t find spikes in health problems like autism, obesity, cancer, and kidney disease that correlate to the introduction of GE foods.

The committee acknowledges small differences in gut microbes in some animal experiments, but conclude that GE foods “are not expected to cause health problems.”

On allergenicity, the committee recognizes that “[t]here are limits to what can be known about the health effects of any food, whether it is produced through conventional breeding alone or in conjunction with genetic engineering.”

All in all, the report concludes, “no differences have been found that implicate a higher risk to human health and safety from these GE foods than from their non-GE counterparts.” But the committee is also careful to say that there are limits to what we can know. Any new food, whether GE or not, “may have some subtle favorable or adverse health effects that are not detected even with careful scrutiny and that health effects can develop over time.”

The report’s discussion of human health also includes some optimism that both GE and non-GE crops with increased concentrations of some nutrients could have “favorable effects on the health of millions of people.”

Crop Yields

The report distinguishes between the potential yields of crops (that is, the maximum yield, under ideal conditions), and their actual yields (after insects, disease, bad weather, or weeds have their way with them).  There’s no evidence that GE crops have increased potential yields, which had been steadily increasing before GE crops were introduced, and continued to increase afterward.

GE crops can, however, help protect yields from pests.

Pesticide Use

Crops with a built-in organic pesticide called Bt have not just reduced insecticide spraying on the acres they’re planted on, they have, in some cases (like that of the European corn borer), reduced the pest population so dramatically that insecticide spraying has gone down on non-GE acreage.

The report notes, however, that insects can develop resistance to Bt (some have).  To head that off, proper management (including refuges, which are areas where Bt crops aren’t planted so insects don’t develop resistance) is essential, and the report expresses concern about the “lack of compliance with the mandated refuges.” Crops engineered with an insecticide work as a part of a pest-management strategy, but they aren’t, by themselves, the solution to insect problems.

For crops that are tolerant to glyphosate, the herbicide in Roundup, the story gets more complicated. While those crops initially decreased overall herbicide use, the report says those decreases have not been sustained.  The committee also specifically rejects the measurement of herbicide application (kilograms per acre or hectare) as meaningful, because some herbicides are more toxic than others. and suggests that “researchers should be discouraged” from reporting those numbers.

The downside of herbicide tolerant crops is that, “in many locations some weeds have evolved resistance to glyphosate.” The report cites one study that puts the cost of managing glyphosate-resistant weeds at $66/acre for corn and $22/acre for soy, an amount that can sometimes make the difference between a positive and negative gross margin.

Better weed management has to go hand-in-hand with the deployment of herbicide-tolerant plants, the report finds.

Biodiversity and Environmental Impact

The report addressed a varied group of concerns related to how GE crops interact with the environment.  Here are the committee’s findings.

  • There’s no evidence of adverse effects of Bt crops on honeybees.
  • Although crop rotation and crop diversity have been declining since 1987, the report didn’t find a cause-and-effect relationship with GE crops. The committee did note that some GE varieties can facilitate “successful management of very large areas of these crops without rotation.” On the other hand, the committee considered evidence that GE crops could enable crop rotations that would be “prohibitively difficult or expensive” without the weed control that comes with herbicide-tolerant crops.
  • Research has not shown that “suppression of milkweed by glyphosate is the cause of monarch decline,” but researchers disagree about whether glyphosate has any impact on monarchs.
  • ‪Although there has been gene flow from GE crops to wild relatives, “no examples have demonstrated an adverse environmental effect.”
  • The report couldn’t find a clear cause-and-effect relationship between herbicide-tolerant crops and no-till farming practices.

Social and Economic Effects

The report makes the point that, when we’re talking about introducing a new kind of crop into our food system, we have to look beyond matters of human and environmental health, and take social and economic issues into consideration:

  •  ‪Overall GE crops have worked out well, economically, for the farmers who have chosen them, but there’s a lot of variation in outcomes.  Insect-resistant crops reduce loss to insects, and herbicide-tolerant crops “tend to reduce management time.”
  • Benefits of GE crops aren’t always available to small-scale farmers, because of the high price of seed and inadequate access to credit, “among other institutional issues”
  • For small-scale farmers to get the economic gains of GE crops, they’ll often need “institutional support, such as access to credit, affordable inputs, extension services, and markets.”  They may need assistance “improving soil fertility, increasing nutrient availability, and optimizing plant density”
  • Regulatory barriers have raised the price of developing GE crops, which makes it more difficult for the private sector to develop crops that aren’t widely planted. This works against having a diverse selection of GE crops.
  • The report notes that some studies have suggested that GE crops “contribute to farmer deskilling.”
  • It’s important to prevent the inadvertent presence of GE crops in non-GE fields, for both social and economic reasons. “Farmers want the freedom to decide what crops to grow,” and non-GE crops command a higher price.  The committee notes that this is often happening: “many areas are successfully growing organic, non-GE, and GE crops.”
  • One important economic issue is trade disruption.  As different countries approve different GE crops at different times, trading becomes complicated.  “Trade disruptions … are likely to continue to occur and to be expensive for exporting and importing countries.”
  •  ‪The report also tackles the very fundamental issue of trust.  It’s “difficult to capture the cost of a loss of public trust in a product, an industry, or the legitimacy of a regulatory system.”


The report says that regulation of GE crops “should facilitate achieving the maximum societal benefits … at given levels of acceptable risk.”  The committee acknowledges that it’s a tall order, because both risks and benefits vary among crops. NAS is clear that it is the product—not the process—that should be regulated.

Other regulatory issues include:

  • Patents (of both GE and non-GE crops) can limit access by “small farmers, marketers, and plant breeders who lack resources to pay licensing fees or to mount legal challenges,” and there’s disagreement over whether patents facilitate or hinder “knowledge-sharing, innovation, and the commercialization of useful goods.” The report predicts that technology “that is of most use to small-scale farmers or farmers of specialty crops will probably have to emerge from public-sector institutions or from public-private collaborations” because the incentives aren’t there for industry to work on those crops.
  • Although the labeling issue is complex and there are “strong nonsafety arguments and considerable public support for mandatory labeling,” the committee “does not believe that mandatory labeling of foods with GE content is justified to protect public health.”
  • “Policy regarding GE crops has scientific, legal, and social dimensions, ad not all issues can be answered by science alone.”  The values and priorities of all stakeholders have to be considered.
  • ‪Regulators need to be proactive communicators, and “transparency and public participation” are “critically important for appropriate, sound, and credible governance.”
  • “The lack of public access to the health and safety data submitted by developers creates distrust in some stakeholders” because “the public cannot judge for itself the quality, objectivity, and comprehensiveness of the materials submitted.”  While the committee recognizes “the legitimacy of the confidential nature of business information,” it urges as much sharing as possible.

Looking Forward

The report sees an important role for genetic engineering, and “the committee expects that its potential use in crop improvement in the coming decades will be substantial.”  Increased nutrition, better nutrient use, decreased greenhouse gas emissions, and pathogen resistance are just some of the ways GE crops can improve human and environmental health, farmer well-being, and agriculture’s sustainability, it says.


Tamar Haspel is a food and science journalist. She can be reached on Twitter @TamarHaspel.


Comments (22)

  1. Robert Wager (May 17, 2016)

    Small-scale farmers may have trouble seeing those economic gains because of the price of seed and lack of access to credit.

    Although credit is a problem, 17 million resource poor farmers now grow GE crops and benefit from these crops.

  2. Amy (May 17, 2016)

    Please also consider, the U.S. Right To Know article ‘GMO science is for sale’, concerning conflicts of interests within the National Academy of Sciences, pertaining to GMO research. Transparency is extremely important regarding; research funding, possible ties to the industry that is being researched, what length of time and where/ how the research data was obtained. I remain skeptical concerning the difficulty to insure proper transparency. Also, the lack of media coverage of reliable studies on the large increase in the use of weed killers (in order to kill the super weeds that have emerged), how these growing practices affect beneficial microbes in the soil, harm to beneficial pollinators, invasion of GMO’s onto non-GMO farms, are bothersome. I believe it shows a lack of concern regarding citizen’s right to know and informed transparency in our news and journalism. Americans deserve transparency, especially when it involves what we put in our bodies. Scores of us are tired of waiting and are speaking out with our wallets, buying as much organic as we can. A lack of proper transparency generally indicates a problem.

  3. Julien (May 17, 2016)

    I know they’re safe to eat, but I avoid them because of practices of large GMO companies like Monsanto, creating round up ready soybeans, which to me indicates an increase of the use of pesticides for at least that particular type of crop. They also force legal battles onto small farmers claiming they’re infringing on the patent when the cause is unintentional and due to cross pollination of nearby gmo crop. I hate all the unknowns out there. And I suppose based on the info in this article then, that I could just avoid all gmo soybean products specifically, but because the gmo industry is so large in general, how can I know that Monsanto or other similarly evil companies don’t have their hand in other types of crops, like corn, which is in everything and everywhere?

  4. Diane (May 17, 2016)

    Sorry…not gonna drink this kool-ade.

  5. Wichar thitiprasert (May 17, 2016)

    Well balance document on the impotant of biotechnology to improve our well being of humanity. GM crops are as safe as coventional…why not take it?

  6. Jason (May 18, 2016)

    Lets see. Congress requests a report. Congress is massively funded by Monsanto. The report is inconclusive regarding the health issue and places plenty “legal disclaimers” within the article. Feel safe much?

  7. Sean (May 18, 2016)

    To Amy : You can not keep claiming new avenues of skepticism in lite of evidence without admitting that you have a bias that no amount of research can satisfy.

    All science is “for sale” but there is a lot more money and fame in researching something that defies pervious studies than quietly prescribing to the “mass conspiracy.”

  8. SENTHIL KUMAR (May 18, 2016)

    It is good joke to read that ” the committee “does not believe that mandatory labeling of foods with GE content is justified to protect public health.”

    They moment they label them , they know the volume of sales crash. Why to pretend so much?

  9. Randy (May 18, 2016)

    We have delt with resistant weeds for years no matter what herbicide we use. Most people never heard of the trizine resistant weeds that were a large problem in the 80s and 90s. Bugs were the same way, they develop a tolerance to insecticides. We solved that problem by applying higher more lethal rates. Since the advent of GMOs I have used much less lethal chemicals and have not seen all of these super bugs and resistant weeds that every one talks about. A lot of it depends on the way you manage your business. It is sad to see the way younger people embrace organic grown food. If they only knew what lethal chemicals are sprayed on them and what the long term side effects might be….

  10. Adrian (May 19, 2016)

    Reporting is more opinion than analysis. No chart or data presented. Mostly unfair to the butterfly and the bee. No specific changes recommended. Unfair to the health implications of the farmer. Only more questions raised about the ethical aspects of the cost and licensing issues. Too many issues were not properly considered and brushed over.

    What will we find out about all the pesticides we’ve eaten over the next 10 to 20 years?

  11. Duncan Asper (May 19, 2016)

    They also said that Thalidomide, DDT and Tobacco were safe. So we are supposed to believe that mutant GMOs and the petroleum based toxic chemicals used to grow them are safe. I think not. GMOs are a threat to all things natural and organic. If they are so wonderful why does big ag and biotech oppose labeling? If they are feeding the world why are there still millions of people, here and abroad, still going hungry? The only purpose they serve is for profit for companies like Monsanto, Syngenta, Dow and factory farms. How much did the pay you for this bogus report?…

  12. Goerg (May 19, 2016)

    pizza hut is the best

  13. Dawn, Montreal Canada (May 19, 2016)

    The entire question for me has been centered on lack of information about practices. Many people in the general public understand that breeding for genetic modification is as old as agriculture itself, but there are real factors that make this new laboratory phase of it disturbing. The term GMO has come to be associated with mouse genes spliced into vegetables, and given the lack of transparency on the part of the agribusiness corporations about what is being modified and how in an information age, it’s understandable that there is little public trust. While it’s unfortunate that some responsible science has been lost to a frankenfood resistance, the industry has no one but itself to blame. “No evidence of harm” isn’t an acceptable substitute for food safety to a public that has seen constant deception and political agendas undermine food security. It’s too reductionist to put the “debate” into for/against terms; it’s more complex than that.

  14. T. Stengel (May 19, 2016)

    VERY disappointed with this once respected organization, as it seems the “science” was allowed to be influenced by Monsanto. – And doesn’t address – – 1) Ever increasing need for pesticides that they also sell and their impact to our air, water & food – 2) Their infiltration of the EPA – 3) Litigious intimidation – 4) Fighting the labeling of our food – 5) The real danger of cross contamination altering the Earths seed supply permanently…. all for the oldest reason ever – GREED!

  15. marty (May 19, 2016)

    well now i can walk off a cliff

  16. Arlene Parkin (May 19, 2016)

    The roundup that’s used with it is toxic!!!! TALK ABOUT THAT,!!!!!!
    So, I ONLY eat organic, like all those in office in Washington!!!!!

  17. Deborah (May 20, 2016)

    I was going to check out the article Amy mentioned via U.S. Right To Know article ‘GMO science is for sale’ but my antivirus software told me the US Right to Know website is a suspicious link that harbors payloads and malware. Just a warning for people going there who don’t have proper anti-virus software.

  18. Rick Sobotka (May 20, 2016)

    For those of you that have not read it yet, I highly recommend reading “Altered Genes, Twisted Truth” by Steven Druker. It helps to set the record straight. It is a shame that an organization like National Geographic that has always positioned themselves as an organization that wants to protect our planet is now in bed with the bio-tech industry. What is the world coming to?

  19. Arthur (May 20, 2016)

    I do not understand the assertions here of lack of transparency about GE crops. All of the information is publicly available in regulatory filings and, most prominently, in patents. If you aren’t informed about these issues, its not because of “lack of transparency;” its because you are too lazy to seek out the information.

  20. Arthur (May 20, 2016)

    Also, the problem many commentators have with the use of pesticides has nothing to do GMOs as such. If you have a problem with pesticides, then you have a problem with the specific GMOs that have pesticide resistance genes. You should be fine with all others, but I suspect that you are not because you dislike the idea of GMOs and any promote the pesticide argument because it is the only tenable complaint against GMOs.

  21. Arthur (May 20, 2016)

    Dawn complains that agribusiness is using a lax standard with “No evidence of harm.” The fact of the matter is that this is strongest claim a responsible scientist can ever make on the matter since it is logically impossible to prove a negative. If you ever hear someone say “This is absolutely 100% safe and has 0 deleterious effects,” its not because that is the case, but that that is an irresponsible scientist making stronger claims than science allows. This is a constant source of misunderstanding between the public (who are unused to encountering responsible evidentiary claims) and the scientific community whose scruples don’t let them make the hyperbolic claims seen everywhere else in human life.

  22. Patricia Wamsley (May 22, 2016)

    Who paid for the study? Monsanto? Our bodies do not need more chemicals or modified foods, we need real foods not filled with scientifically created garbage!