Here’s what the National Academy of Sciences has to say about GMOS

This morning, the National Academy of Sciences (NAS) released a consensus report titled “Genetically Engineered (GE) Crops: Experiences & Prospects”. You can download the full 400 page report which includes a four page summary here. The public release of the report was accompanied by a webcast including a presentation of the report followed by a question and answer session. My notes on the webcast including screen shots of many of the slides are synthesized below. I apologize for any missing slides or points. None were omitted intentionally. As a scientist, I tended to focus my notes more on human health and the environment and less on social/economic points.

The NAS is a private, non-profit organization that “is charged with providing independent, objective advice to the nation on matters related to science and technology. Scientists are elected by their peers to membership in the NAS for outstanding contributions to research. “

Volunteers for the NAS committee to assemble the consensus report were vetted for potential conflicts of interest. The committee was composed of a very diverse range of scientists and experts from a variety of different topic areas ranging from entomology to science communication. The committee was initially divided, as there were many different views on the prospects and progress of genetically engineered crops. However, all members were required to back their claims with evidence as the discussion progressed, and they ultimately came to a consensus that best reflects the available data.


In analyzing the issue, the committee looked to two decades of scientific literature including nearly 1000 articles. They also listened to input from 80 diverse speakers, and reviewed over 700 public comments. These videos and other materials have all been archived and are publicly available. The study was sponsored by the New Venture Fund, the Gordon and Betty Moore Foundation, the Burroughs Wellcome Fund, the U.S. Department of Agriculture, and the National Academy of Sciences. The report had 26 diverse reviewers. The committee had to respond to each of their comments and defend their conclusions with evidence.

methods 2

methods 3

The first key message from the committee emphasized the increasing difficulty of differentiating crop improvement technologies that qualify as GE from those that do not (you can read my personal explanation of this issue here). The chair of the committee Dr. Fred Gould likened this to the invention of cell-phones, cameras, and lap-tops which were once all distinct technologies that now have overlapping functions.


For this reason, the committee contends that it is impossible to “make sweeping generalizations about the benefits and risks of GE crops”. For the report, they mainly focused on three of the most widely grown GE crops: corn, cotton, and soybeans. The report also focused on the two most commonly utilized traits: insect (BT crops) and herbicide (RoundUp-Ready crops) resistance.

The committee generally concluded that insect resistant crops result in increased yields due to fewer losses from pests. Planting of insect resistant crops also correlates with a decrease in the application of synthetic pesticides and an increase in biodiversity. However, improper management of insect-resistant crops can and has resulted in the evolution of resistant insects.

insect resistance

They also concluded that the planting of herbicide-resistant crops can lead to an increase in yield. Beyond yield, the technology is substantially useful to farmers for several reasons. Herbicide-resistant crops allow farmers to apply a single herbicide where they might before have used many at a time when it is optimally convenient, safe, and physiologically advantageous for their crops.

My screenshot of this slide did not turn out, so I looked it up in the archives

The committee also notes that weeds (like the insects) have evolved resistance to this herbicide creating a huge challenge for farmers who will need to change their management strategies. The committee also made a point to emphasize that comparisons of kilograms of herbicide use before and after herbicide-resistant crops were widely adopted is not meaningful unless the health and environmental impacts of those herbicides are also compared.

herbicides 2

The committee’s analysis of the environmental impact of GMOs, revealed some evidence of gene flow from GE crops into wild ecotypes, but only under experimental conditions. The committee in general found that there was no evidence of environmental problems caused by growing GE crops. There was also no direct connection between the use of herbicide-resistance crops and no-till practices as farmers had already begun to move away from tilling prior to the advent of GE crops.


In response to the question of whether or not GMO crops are contributing to yield increases, the committee contends that they are. They acknowledge that what’s good for one farmer is not good for another, but farmers in general are gaining from the technology.

yield rate

That said, as these graphs show, there is not a spike in yield increase following the advent of GE crops (indicated by the vertical purple line). This likely demonstrates that changes in management practices and genetics through conventional breeding and other crop genetic improvement methods are equally as important for increasing crop yield. New types of GE crops could potentially contribute to the rate of increase depending on the traits introduced and the socioeconomic/cultural/legal factors that influence the adoption of new GE crops.

yield 2

To assess the impacts of GE crops on human health, the committee analyzed over 200 existing studies, looked for changes in patterns of human health before and after the adoption of GE foods, and compared the overall health of people in the United States and Canada (where GE crops are widely grown) with the health of people in Europe (where they are not). The committee reported that many of the existing animal studies were not optimally designed.

human health 1

Reports of long-term health of livestock fed GE diets and studies comparing nutrient and chemical compositions of GE food were more reliable. From these, they did not find any reliable evidence linking GE foods to health concerns. They also did not find any differences in human health that correlated with the adoption of GE crops.

human health 2

Given the lack of legitimate health concerns associated with GE foods in general, the NAS proposed a new system for regulating future GE foods. The proposed regulatory approach would compare the “omics” (levels of various compounds including nucleic acids, proteins, and metabolites) of new crops with the same levels in existing varieties.

regulation 1

New crops would then be categorized as Tier 1 if there are no differences or Tier 2 if there are differences that have no expected health or environmental effects. Tier 1 or 2 crops would not require any further testing. If the new crops have differences with potential for health or environmental effects or differences that cannot be interpreted, they would be classified as Tier 3 or Tier 4 respectively and would require further testing. Under this system, most new varieties would fall under the category of Tier 1 or Tier 2.


On the issue of labeling, the committee concluded that because there are no health effects associated with GE food, there is no justification for labeling them on the basis of food safety. There are, however, policy reasons for which labels might be instituted such as consumer autonomy. It is outside of the legal authority of the FDA to institute a label for policy/cultural reasons, so labels would need to be mandated at the congressional level.

Read what a handful of other academic scientists had to say about the report here.



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