NASGMOreportDespite the fact that numerous scientific and health organizations around the world have examined the evidence regarding the safety of genetically modified organisms (GMOs) and found them to be completely safe, there remains a public controversy on this topic. In fact a Pew Poll found that while 88% of AAAS scientists believe that GMOs are safe for human consumption, only 37% of the public do – a 51% gap, the largest in the survey.

This gap is largely due to an aggressive anti-GMO propaganda campaign by certain environmental groups and the organic food industry, a competitor which stands to profit from anti-GMO sentiments. There is also a certain amount of generic discomfort with a new and complex technology involving our food.

Because of all this, the National Academy of Sciences put together an expert committee to systematically review all the evidence regarding this new technology. Their thorough 407 page report is now available.

They pulled together experts with diverse backgrounds, and also took public comment and solicited input from a wide range of interests. They decided specifically not to rely on any previous review, but to conduct their own review of the primary literature.

The NAS report’s findings

Health and safety of GMOs

The report gives this summary of its findings regarding the health risks of GMOs (for which the report uses the synonym “genetically engineered/GE”):

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. 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.

This coincides with every other major review of the evidence. The bottom line is that there is no particular reason to believe that currently available GM crops pose any health risk or that they are different with regard to their safety and nutrition from their conventional analogues. There is also nothing about the current processes used to generate GMOs that would theoretically pose a unique health risk.

It is especially compelling that over the last two decades, animals and humans exposed to GMOs have not experienced any relative increase in any major disease.

Economic and environmental issues

Introduction of available GMOs has generally had a positive effect on farmers and the environment. They write:

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.

Essentially what their analysis is saying is that GMOs have been a useful tool to increase profits for farmers and can be very beneficial to the environment, but they have to be used correctly and are not a panacea. This makes GMOs, therefore, like any other technology.

Obviously farmers face complex economic challenges, especially in some parts of the world. The availability of GM crops has been a positive factor, but does not address all the complex issues faced by farmers. I do not consider this a criticism, but rather an obvious truism.

The same is true for the environmental effects. 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.

In both cases, however, the report also notes that if these technologies are overused then pesticide and herbicide resistance will become a problem. They recommend, as have many previous experts and reviews, that Bt and herbicide-resistant crops be used as part of integrated pest management.

To summarize the summary – when used properly, GMOs are good for farmers and good for the environment. GM foods are safe for animals and humans.

Testing and regulation

Another interesting area of the report is their comment on testing and regulation. They essentially argue that current regulations are based upon a false dichotomy, between conventional and genetically modified organisms. They point out that emerging technologies are increasingly blurring the lines. Gene editing is not quite genetic engineering, and genetic technologies are being used to guide crop breeding, for example.

They argue, and I agree, that it is not rational to base requirements for testing on the process but rather on the outcome. They write:

Emerging genetic technologies have blurred the distinction between genetic engineering and conventional plant breeding to the point where regulatory systems based on process are technically difficult to defend. The committee recommends that new varieties—whether genetically engineered or conventionally bred—be subjected to safety testing if they have novel intended or unintended characteristics with potential hazards.

This makes a great deal of sense. Conventional breeding, use of forced hybridization, or mutation farming, is not inherently safer than using any of the increasing number of technologies for more directly altering the genetic makeup of a crop. What matters is if there are novel traits of unknown safety, in which case they should be tested.

This blurring of the lines should also frustrate labeling efforts, since the entire notion behind labeling is based on the false dichotomy that the NAS report just demolished.


As one might predict, responses to the report have coincided with previous ideological leanings. The report is so large and covers so much territory that it provides a Rorschach test – people see in it what they want.

For example:

Michael Hansen, PhD, senior scientist with Consumers Union, said, “When it comes to GMO labels, the NAS report points out that there are value choices that consumers want to make when they shop for food. We’re pleased to see that the report cites the wealth of polling data showing consumers want GMO labelling.”

They say the report provides reasons for GMO labelling, when actually it doesn’t. It just refers to public opinion, but from a scientific point of view it entirely removes the rationale for labelling.

This NPR headline is typical of another dubious negative response: “GMOs Are Safe, But Don’t Always Deliver On Promises, Top Scientists Say.”

The promise that GMOs have not delivered on, according to NPR, is that they have not substantially increased yields. This is a common criticism of the GMO industry. However, the currently available GMOs are not intended to increase yield. They do reduce loss and make yields more predictable, which is very useful to farmers, making this a highly misleading criticism and a cherry-picked point to feature in a headline.

This says nothing, also, about the technology, only its current applications. There are researchers working on traits that could substantially increase yield. Some scientists argue we will need GM technology to keep up with growing demand for crops, especially with a changing climate.

Finally, it is no surprise that some are already lazily dismissing the NAS report as biased:

“The makeup of the panel is pretty clear. People are coming in with a perspective that is pro-genetically engineered crop,” says Patty Lovera, assistant director of Food & Water Watch.

Meanwhile the reality is that the committee is almost entirely made up of independent academics from major universities with not significant ties to industry. At worst some committee members may have done some consulting for industry, but that is a common and insignificant connection without any conflict of interest.

Conclusion: Another refutation of GMO fearmongering

The NAS report adds to the growing list of comprehensive scientific reviews of GM technology finding that they are safe, good for farmers, and good for the environment when used as part of integrated pest management.

The dire warnings of anti-GMO groups are not backed by evidence; in fact they are directly contradicted by the evidence. It is ironic that environmental groups oppose GM technology when the result of their opposition is to harm the environment.

The clearest evidence relates to the health effects of GM technology and currently available GMOs. GMOs are safe for humans and animals. Hopefully the NAS report will help move the needle on public opinion, which is currently highly divergent from reality.




Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.