Our Approach To GMOs

What are GMOs?

“GMO” stands for “genetically modified organism.” The technology used to genetically modify an organism is referred to as genetic engineering, and an organism that has been modified in this way is called genetically engineered (GE).

The genetic engineering process typically entails isolating DNA (genetic material) from one organism (an animal, plant, virus, or bacteria), inserting it into the DNA of another organism, and ensuring that the traits associated with the inserted genes are expressed in the modified organism.

Crops that have been modified to express new traits via genetic engineering are also called “transgenic.”

So far, GE crop plants have been the source of virtually all GMOs for sale as food or food ingredients in US grocery stores. However, a GE animal, the AquaAdvantage salmon, was recently approved by the US Food and Drug Administration (FDA). It is not available in grocery stores at this time.

Is genetic engineering different from conventional crossbreeding?

Important differences distinguish genetic engineering from conventional breeding. In conventional crop crossbreeding, also called hybridization, two different strains of the same, or closely related, plant species cross-pollinate, thereby sharing their DNA, and this produces offspring that contain genes from each parent.

The mature seeds from the crossed plants are, in turn, planted and grown out. Plant breeders then select the offspring displaying the most desirable combination of traits. Genes from other organisms that are not sexually compatible with the crop, such as animals or bacteria, are not involved.

Conventional crossbreeding has been used to advance plant and animal productivity and vigor worldwide for centuries. It remains the most reliable and widely used method to tap the genetic diversity that exists in the genomes (the set of genetic material present in an organism) of all plants and animals. This type of breeding thus benefits from mechanisms that plants and animals have evolved to ensure their genetic integrity – and hence their survivability – is not threatened by undesirable mutations or by damage from pathogens.

Contrary to conventional crossbreeding, genetic engineering involves purposefully moving foreign DNA into organisms in the hope of gaining expression of a new, desirable trait. To insert foreign DNA, scientists must use techniques that evade or overwhelm the natural defense mechanisms of the plant or animal against viral pathogens and undesirable mutations.

The techniques used to move foreign DNA into today’s commercial GE crops are nearly always imprecise. Genetic engineers have no control over where the foreign DNA is lodged within a recipient plant’s DNA, nor can they control how many copies of the foreign DNA end up being expressed.

The promoter genes and other regulatory sequences moved into a GE plant or animal can also have unpredictable impacts, for example on the expression of other genes in the recipient’s genome, possibly altering responses to environmental stresses, pests, or pathogens.

These are vital and important differences that contrast with conventional breeding. Scientists are making progress in understanding the consequences of these differences. For example, new GE breeding techniques are emerging that will reduce the potential for some kinds of unexpected effects triggered by the location of the expression of foreign DNA in transgenic plants and animals.

Basics of genetics

DNA (deoxyribonucleic acid) is a chemical substance that makes up the genetic “blueprint” of each living organism. Each cell of an organism contains DNA.

One important function of DNA is to serve as a template for the construction of a vast array of proteins that carry out specific functions for the organism. These functions include regulating growth, metabolism and responses to stimuli and stresses such as excessive heat or an attack by a pathogen.

DNA provides the templates for proteins in units called genes. Genes are organized in specific orders within chromosomes, which are distinct packets of DNA wrapped in structural proteins. At any given time, most genes are not active. Genes are turned on or off by signals from the cell. These signals are, in turn, triggered by environmental conditions, among other things.

Evidence that genetically engineered foods may impact human health

There is growing concern that GE foods may, under some circumstances, impair the human immune system, alter the composition of bacteria in the human gastrointestinal tract, and/or disrupt the function of certain human genes.

After decades of use, it is also now clear that most GE crops require more frequent applications of herbicides and an ever more potent mix of insecticides and GE proteins to control insects.

In addition – and worrisomely because of both human health risks and farmer costs – many GE crops now grown around the world have been demonstrated to be more susceptible to fungal diseases than equivalent non-GE crops, and hence require farmers to apply fungicides to avoid yield losses.

Rising use of fungicides

Hybrid corn was introduced in the US in the 1940s. Until then, corn farmers had never applied fungicides on more than 1% of national corn acres. By 2010, according to the USDA, farmers were spraying fungicides on 11% of national corn acres, and the proportion has risen incrementally since.

Clearly, there is a corn plant-health problem in the US, which is almost certainly rooted in GE technology and in the steady increase in the number of corn seeds planted per acre.

The rising reliance on pesticides and findings of possible adverse health impacts from consumption of GE foods intensify concern that some people may suffer health setbacks as a result of GE technology. This underscores the need for government agencies and independent scientists to utilize cutting-edge research techniques to accurately identify and quantify possible risks of consuming GE foods.

We are convinced of three critical points regarding GE foods and human health.

First, as of late 2015, there is no clear and convincing evidence in the peer-reviewed literature that shows that consumption of GE crops and of foods manufactured from them have caused a substantial increase in health problems in the US population.

Second, very little funding has been available to independent scientists to study the long-term impacts of GE foods on human health in the US, so that any impacts that might have occurred and continue to occur have remained undetected.

Third, the potential severity and range of adverse human health impacts triggered by today’s GE crop and animal technology is definitely rising, and the existing database and science supporting risk assessment are grossly inadequate. Moreover, there has been virtually no systematic, post-market approval surveillance to check for unanticipated, adverse health impacts from GE organisms.

We can, and must do better.

New and emerging evidence

A number of recent discoveries that have revolutionized our understanding of health and disease have shed light on how consuming GE crops and foods might impact human health.

The first discovery is that the immune system plays a key role in most of our chronic illnesses, even those not related to infections or cancer. Most diseases are now understood to involve a component of immune dysfunction, also known as “inflammation.” For instance, although cholesterol plaques are associated with cardiovascular disease, inflamed cholesterol plaques are a much stronger predictor of adverse cardiovascular events than simply the presence of plaques alone.

Inflammation also plays a role in cancer, Alzheimer’s disease, arthritis, infertility, obesity, depression, autoimmune disease, dementia, eye problems, and a vast number of other chronic conditions.[1]

Thus, a chemical, drug, food additive, or GE protein that will be widely ingested should not be declared safe until science has definitively shown that it does not trigger inflammation.

The second emerging concept involves the role of the microbes that inhabit humans. Trillions of bacteria coexist with us, inside our bodies and on our skin. For example, the human gut contains 10 times more bacterial cells than the human body contains human cells.

Most bacteria coexist with us harmlessly, and many play important roles in our metabolism. Bacteria also, in effect, train and control our immune systems.[2]

In view of the many adverse consequences of inflammation described above, the role bacteria play in orchestrating our immune response results in far-ranging impacts on health and disease.[3]

Beneficial bacteria

Beneficial bacteria also impact other aspects of metabolism. For example, researchers studying the impact of artificial sweeteners, which were thought to be helpful for people limiting their sugar intake, found that these substances altered the composition of beneficial bacteria in the human intestine, and that these bacteria in turn caused changes in glucose regulation that raised the risk of diabetes.[4] This was an unexpected finding that contradicted the “common-sense” understanding that artificial sweeteners would be useful for people at high risk of diabetes.

Thus, before declaring that a chemical or substance is safe, we should strive to understand its impact on gut and other bacteria that coexist with humans.

The third important change in our understanding of health and disease is the discovery of the crucial role of epigenetics, which is the study of how factors other than DNA switch genes on and off.

Although our genes remain essentially unchanged from birth to death, the conditions and frequency of their expression can change over time. Such changes are called “epigenetic” because they involve how cells read genes, and not the genes themselves. In short, the gene remains the same; what changes is when and how strongly it is expressed.

Some environmental influences, such as exposure to certain pollutants including pesticides, can have epigenetic effects that are heritable, and hence passed on to subsequent generations.[5]

Thus, it is crucial that public-sector scientists be given the resources needed to study the epigenetic impacts of new GE technologies and of their associated pesticides before these technologies are declared safe and approved for unrestricted use. Premature declarations could impact us – and subsequent generations – in ways we do not yet understand.

Much of health and disease depends on the way that chemicals influence gene expression, gut bacteria, and inflammation, regardless of how the chemicals get into our body. This is why agriculture and food have such far-ranging effects on our health.[6]

Many chemicals and GE foods are presently not tested for their effects on the immune system, on human reproduction, on the microbiome in our gut, or on gene expression and inheritance of gene expression patterns.

Lack of testing of these effects indicates that our regulatory policies and risk assessments have fallen far behind our science and can no longer be truthfully characterized as based on, or consistent with, modern science.

What should researchers be asking?

Crucial questions to consider in determining the possible impacts of GE foods on human health include:

1. Are GE proteins absorbed into the human bloodstream?

Two types of GE plants comprise approximately 99% of GE crops in the US:

  1. Bt-toxin-producing corn and cotton plants, which resist insect pests by essentially producing a pesticide substance within the plant itself; and
  2. “Roundup Ready®” plants, developed to withstand repeated spraying of the herbicide Roundup®.

Manufacturers initially seeking approval for Bt-toxin-producing GE plants argued that Bt toxins were safe for humans. (There are hundreds of different forms of Bt toxins, see our section on Bt toxins.)

One argument for safety was that these toxins would be broken down by stomach acid. However, a 2010 study on cows showed that Cry1Ab (one type of Bt toxin) was not entirely broken down in the bovine digestive system: it was found in the cows’ stool, but not in their bloodstream or milk.[7]

A study involving humans found recognizable breakdown products of Cry1Ab in the blood of most people tested.[8] Evidence that certain Bt toxins may be harmful to mammals is presented here.

New research therefore undermines the assumption that GE proteins are completely broken down by our stomach acid and do not enter our bloodstream.

What is more, almost no effort has been made to assess the potential toxicity, or other impacts, of the fragments created when GE-crop Bt toxins break down in our bodies or the environment. The number of unanswered questions is steadily increasing, in step with the American public’s exposure to greater diversity of Bt proteins and their fragments.

2. Does eating GE foods increase our exposure to certain pesticides?

Most GE crops grown in the US were genetically engineered to withstand exposure to pesticides (insecticides and herbicides). Their cultivation has thus resulted in increased human exposure to pesticides as well as GE insecticidal proteins, as described above.

In the case of Bt-toxin-producing corn for example, a variety of proteins toxic to Lepidopteran insects (moths and butterflies) are continuously produced in all the growing tissues within the Bt-GE corn plant, including in the kernels on an ear of corn.

Roundup Ready® soybeans, corn, canola, alfalfa, and sugarbeets have been engineered to tolerate exposure to the herbicide Roundup®, so that when the herbicide is applied in a field, the weeds are killed while the crops remain unaffected. However, over a dozen glyphosate-resistant weeds have developed tolerance and now survive in US crop fields planted with Roundup Ready® crops.

GE food proponents argue that the cultivation of GE crops has decreased the use of certain insecticides.[9] This is generally true especially in the first five to ten years after GE-Bt crops are planted, but changes in the mix of insects thriving in these fields, coupled with the emergence of insects resistant to Bt toxins, eventually leads to increases in insecticide use.

Although it is true that there is less liquid insecticide sprayed on the leaves of these crops than would be sprayed on a similar conventionally grown crop, an insecticidal endotoxin (Cry1Ab for example) is now part of the plant itself, synthesized inside plant cells and present throughout the tissues of the corn plant, from the roots to the kernels themselves. The potential impact on our health from ingesting these GE toxins is not well understood and may be profound in some individuals (see our Bt-toxin article).

In the case of certain herbicides (such as Roundup®, which contains glyphosate), their use has increased dramatically because of GE crops. In sum, GE foods are putting us on a path toward exposure to more of certain pesticides, and more pesticide overall.

Industry has recently acknowledged that the number of weeds that have developed resistance to glyphosate is so great that it must now engineer resistance to another older, higher-risk herbicide called 2,4-D into GE corn and soybeans. In some cases, one to three additional herbicide-active ingredients must be sprayed to keep ahead of glyphosate-resistant weeds. New plants, now genetically engineered for resistance to multiple herbicides, have been developed, and farmers are expected to spray crops with both glyphosate and 2,4-D (the combination is called Enlist Duo®) and often other herbicides as well.

3. Are we using current research methods to shed light on the risk or safety of GE foods?

In general, toxicological risk assessments at federal agencies in the US have not kept pace with our scientific understanding of health and disease. The best type of study to determine whether a GE food is safe would be a controlled, long-term human feeding study.

Such studies on humans are not likely to be conducted, however, and few long-term studies on animals have been done, because of cost. In addition, long-term animal studies do not shed light on a number of the human diseases presently on the rise (listed here and here), for which exposure to GE-crop proteins and/or the pesticides associated with GE crops might be a risk factor.

To perform valid risk assessments and support sound public health decisions about today’s GE crops, independent scientists should study the impact of GE foods and pesticides on such variables as:

  • The expression of genes (epigenetics) known to affect health outcomes;
  • The levels of cytokines (indicators of inflammation);
  • The composition of gut microbes;
  • The physiology and gene expression of gut microbes; and
  • Micronuclei, 8OHDG or other early predictors of cancer risk

In evaluating risks arising from 21st century GE crops, it is irresponsible, and indeed perhaps dangerous, to rely solely on 20th century toxicological study designs and evaluations.

4. “Innocent until proven guilty” or “do no harm”?

US toxicological assessments typically assume that synthetic chemicals are innocent until proven guilty, so as to not unjustly incriminate the manufacturers of these chemicals. Thus, regulatory agencies will not ban a specific pesticide or GE organism that is already on the market unless harm to humans and/or the environment can be proven to exceed the benefits stemming from applications of the pesticide or planting of the GE crop.

We contrast this with the more conservative, medical model of “do no harm.” A procedure or medication is not prescribed if it has the capacity to be harmful out of proportion to the benefit it is expected to deliver (to the individual taking the medication). In our opinion, this is a more appropriate standard for government decisions that impact what is in our daily diet.

5. Are we just looking to avoid cancer and death, or are we concerned about how the key factors underlying our health are impacted?

We now understand that most of the chronic illnesses presently on the rise are diet-related and might be the result of disruptions in beneficial bacteria and in genes that participate in the body’s immune response (see our section on GMOs and Illness).

Avoidance of these disruptions is the standard by which we should judge new food substances, technologies, GE crops, and environmental toxins.

When it comes to safety testing for the marketplace, traditional toxicology involves concepts mostly related to chemical poisoning and reproductive cancer risk. If we really want to know how a substance we consume daily might affect our health, we should measure how it alters products of the immune system (such as cytokines, which indicate inflammation). We should also characterize the substance’s impact on complex networks of beneficial bacteria in the human GI tract.

So far evidence indicates that glyphosate – the active ingredient in the herbicide Roundup® – can impact the gut microbiome.[10] Evidence also indicates that it can have a deleterious effect on the immune system.[11]

More research is needed to understand when, and to what extent, such adverse impacts will materialize. The studies need to be designed, funded, and reported without conflict of interest or fear of retribution from any quarter.

We must rely on sound science in addressing the many unanswered long-term, health-related questions about most of the GE foods grown in the US. This requires changes in policy and funding priorities, so that qualified scientists who are independent of the biotechnology industry have the time and resources needed to conduct state-of-the-art experiments.

If there is no funding for this work, there will be no new science, and therefore no answers and no resolution of lingering safety concerns.


No substance or GE crop can be called safe until its impacts on our immune system, gut bacteria, reproductive capability, genes, and the mechanisms underlying cancer have been thoroughly explored. US regulatory agencies have not investigated these areas of study adequately, or, in some cases, at all.

Questions about the safety of GE food are based on sound, up-to-date science and are put forward in the public interest. Understanding of cutting-edge science is the very basis for questioning the safety of GE foods.

Only well-designed and carefully conducted studies by independent scientists can put to rest concerns about GE organisms and differentiate between applications of GE technology that are almost certainly safe, and those that might pose health and/or environmental risks.

© 2015 GMO Science. All Rights Reserved


  1. Prasad S, Sung B, Aggarwal BB. 2012. Age-associated chronic diseases require age-old medicine: role of chronic inflammation. Prev Med, May;54 Suppl:S29-37.
  2. Yudkin JS, Kumari M, Humphries SE, Mohamed-Ali V. 2000. Inflammation, obesity, stress and coronary heart disease: is interleukin-6 the link? Atherosclerosis. Feb;148(2):209-14.
  3. Cho I, Blaser MJ. 2012. The human microbiome: at the interface of health and disease. Nat Rev Genet, Mar 13;13(4):260-70.
  4. Suez J, Korem T, Zeevi D, Zilberman-Shapira G, Thaiss CA, Maza O, Israeli D, Zmora N, Gliad S, Weinberger A, Kuperman Y, Harmelin, A, Kilodkin-Gal I, Shapiro G, Halpern Z, Segal E, Elinav E. 2014. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature Oct; 9;514(7521):181-6.
  5. Manikkam, M, Haque MM, Guerrero-Bosagna C, Nilsson EE, Skinner MK. 2014. Pesticide Methoxychlor Promotes the Epigenetic Transgenerational Inheritance of Adult-Onset Disease through the Female Germline. PLoS One July 24;9(7):e102091.
  6. Trivedi MS, Shah JS, Al-Mughairy S, Hodgson NW, Simms B, Trooskens GA, Van Criekinge W, Deth RC. 2014. Food-derived opioid peptides inhibit cysteine uptake with redox and epigenetic consequences. J Nutr Biochem, Oct;25(10):1011-8.
  7. Guertler P, Paul V, Steinke K, Wiedemann S, Preissinger W, Albrecht C, Spiekers H, Schwartz FJ, Meyer HHD. 2010. Long-term feeding of genetically modified corn (MON810) – Fate of Cry1Ab DNA and recombinant protein during the metabolism of the dairy cow. Livestock Science, 131(2-3):250-9.
  8. Aris A, Leblanc S. 2011. Maternal and fetal exposure to pesticides associated to genetically modified foods in Eastern Townships of Quebec, Canada. Reprod Toxicol, May;31(4):528-33.
  9. Duke SO, Powles SB. 2008. Glyphosate: a once-in-a-century herbicide. Pest Manag Sci, Apr;64(4):319-25.
  10. Shehata AA, Schrödl W, Aldin AA, Hafez HM, Krüger M. 2013. The effect of glyphosate on potential pathogens and beneficial members of poultry microbiota in vitro. Curr Microbiol. Apr;66(4):350-8.
  11. Astiz M, de Alaniz MJ, Marra CA. 2012. The oxidative damage and inflammation caused by pesticides are reverted by lipoic acid in rat brain. Neurochem Int, Dec; 61 (7): 1231-41.

Thank you so much for this website. Given that one of the main root influences of our health is diet, I believe the topic of GM foods is undeniably important. Having a site where the state of evolving science is presented and discussed is a huge contribution. I will be referring colleagues and patients alike to here.

Nathalie Bera-Miller, MD, MPH

Functional/Integrative Medicine Physician

How refreshing and important to have a place where we can find scientific facts on the true effects of GMO foods. Kissinger said, “Control food and you control the people”. Corporations should not be the ones controlling our food, we should be!

Lonna Larsh, MD

Thank you for making a website on genetic modification of food based on data rather than assumptions. This is important for people to have the most up to date, impartial and accurate information so that they can make these decisions about what to eat. I will certainly share this with my patients to help them be and stay well informed.

Janet Lea Chene, MD