GMOs have a bad name.  This is a fact. The reaction of many people to the term “GMO” is negative. That negative reaction likely stems from several vague concerns: that of humans recklessly altering that which is “natural,” or of the potential to damage “natural” biodiversity, or the loss of freedom of choice that comes with unknowingly ingesting GMO food. However, the most common, and most serious concern of all is that of safety. How could we possibly know that GMOs are safe? There are diseases out there that seem to be increasing in prevalence and we don’t know what causes them – could it be the relatively recent introduction of GMOs?

Science can help with the questions of alteration of “natural” organisms and biodiversity, though these are questions we will not try to answer in this post. The question of freedom of choice, or consent, or “right to know” is strictly an ethical one. The one question here that science is most equipped to answer is one about safety. That is because we have developed very sophisticated methods for hazard identification and risk assessment over the years (and after learning some very hard lessons in the past), and because the government regulatory agencies around the world have dictated, right from the start of the GMO revolution, that new products need to be scientifically proven to be safe. Today, we will look objectively and scientifically at the available data to answer this most basic of questions.

Are GMO foods safe?

What is a GMO food? Let’s start there. This is not a straightforward question to answer from a scientific perspective. Over the last few thousand years mankind has radically altered the genetics of almost everything we eat – from plants and animals, to seafood and fungus. We changed these organisms by artificial (human-driven) selection. Some of this was quite intentional, like selective breeding of crops and animals, while some has occurred unintentionally, but as a result of human behaviors. It should be noted that this is not a distinctly human trait: Many animals develop symbiotic relationships with their foods – selectively spreading the seeds of strains they like to eat over many generations.  Remarkably, ants were farming millions of year before humans.

GMOs in the context of today’s discussion are not produced by selective breeding, or even advanced plant breeding (which may purposely introduce mutations to speed up the “evolution” of the plant). GMOs in our case are defined as organisms that are made by modern genetic engineering techniques that allow us to insert a new gene (or often a small number of genes) into that organism’s DNA in order to improve very specific traits. Here are some of the most common examples grown in the United States:

1. Canola: engineered to be tolerant to herbicides and produce more canola oils
2. Corn: engineered to resist insect damage, be tolerant to herbicides, and be more drought tolerant.
3. Cotton: engineered to resist insect damage and be tolerant to herbicides. Interestingly, people do eat cotton – in the form of cottonseed oil.
4. Papaya and squash: engineered to resist damaging viruses
5. Potato: Engineered to resist a damaging virus and to produce a better ratio of starches
6. Sugar beet: engineered to be tolerant to herbicides
7. Soybeans: engineered to be tolerant to herbicides and produce more oils.

You can also buy other genetically modified crops grown in other countries, and even genetically engineered salmon! It may come as a surprise to you how much of your  food is GMO. Over 85% of all the corn grown in the US is GMO, over 90% of the soy, cotton, canola, and sugar beets, 75% of the papaya. Due to the ubiquitous nature of these products – soy (soybean oil, tofu, tempeh, soy milk), corn (corn starch, corn oil, high fructose corn syrup), canola oil, sugar from sugar beets, potatoes, etc. – GMO foods have been practically unavoidable in the US food supply for twenty years.

How are GMO food products different from typical plants? GMO plants generally contain between one and eight genes that have been purposefully introduced by scientists. These genes encode proteins, which are then produced by the plant to give the plant favorable traits. Many of the most widely used genes come from bacteria that are found naturally in the soil and developed these proteins as natural defenses against insects or other bacteria. There are over 30,000 protein-encoding genes in corn (more than humans have!), and GMO corn differs from non-GMO corn by at most eight proteins. So in this case, GMO corn is more than 99.97% identical to “natural” varieties of corn. I put the term “natural” in quotation marks because the non-GMO varieties of corn have still been genetically altered by humans – it’s just that this “engineering” took place over thousands of years using selective breeding and artificial selection.

The newly added proteins are often expressed only in the non-edible parts of the plant, though some will end up in the food itself – very low levels, but often detectable. Will you eat the proteins encoded by these new genes? In all likelihood, yes, you will. But should you be worried?

How might GMO food affect human health?  The product of these genes are proteins, and since this is food, the plan will be to eat it. What happens when humans (or any animals) eat proteins? The proteins get digested, generally down to the individual amino acids they contain. Since  these proteins were made within the plant, they are made of the same amino acids  as the rest of the protein in the plant, and in all food. And that’s the important point – if a protein is completely digested to the individual amino acids, it’s just like any other food. All organisms (including you) are made of these amino acids – amino acids are safe. The sugars and oils, which are often what we are most interested in eating, are unaffected by the newly introduced genes, except in cases (like soy and canola) where the new proteins improve the yield of naturally-occurring sugars and oils.

There are two ways that a protein, after being eaten, can affect human health, and both involve it failing to be completely digested down to basic amino acids. While rare, there are some proteins that are resistant to degradation by stomach acid and are specifically toxic to animals that eat it. Ricin (found in castor beans), which is one of the most toxic substances known, is partially resistant to degradation in the stomach, and causes serious gastrointestinal toxicity when ingested. However, such degradation-resistant orally toxic proteins are rare – most toxic proteins are injected (like venom from insects and snakes) or produced by bacteria that cause disease inside the body. Furthermore, we know why they are so stable and toxic, so it’s easy to avoid adding genes that encode such proteins.

The second possible adverse effect of a protein is allergenicity – causing an allergic reaction. This is the adverse effect, or toxicity, that health authorities are most concerned about with GMOs. In most GMO foods, the main concern is that the newly introduced protein might be allergenic itself. For soybeans, in particular (which are already allergenic to some people), there is also a risk that the new proteins can somehow increase the allergenicity of the soybeans – such that more people become allergic to the soy or that people who are already allergic have more severe reactions to it.

All new GMO foods are tested for allergenicity. The details of these tests are beyond the scope of this discussion, but they are robust – the proteins are quantified in the food, and their digestion in the stomach is monitored. They are tested in animals. There has never been a confirmed case of a GMO food causing an allergic reaction (that would not also occur with the “natural” form of the food). Some people have claimed to be allergic to GMO food.  There was  a well-publicized article published in a 2013 issue of Elle magazine in which the author claimed to suffer from an allergy to GMO corn .  This, and all other such cases have never been confirmed to be related to the newly introduced GMO proteins. There has even been a documented case where the testing worked and development of a potentially allergenic soy plant was halted  due to allergy concerns, so the plant was never brought to market or consumed by a human. An increase in allergic reactions will always be a theoretical risk with new GMO foods, but the scientists making these products, along with the governmental health authorities have made it a very high priority to avoid such reactions. To date, they have been successful.

What about the other claims of GMO-related health effects? You’ll hear that GMO food cause cancer, or even autism. There is zero data to support these claims, nor do they make much biologic sense. Amino acids don’t cause cancer. Again, you are literally made of amino acids.  No one knows what causes autism, but simple amino acids certainly aren’t the culprit. There are a lot of scientific studies showing that there are no adverse health effects of GMO foods – too many to link to here. If you are interested in a comprehensive review of the literature, check out this study from the National Academy of Sciences.

So why do so many people think GMO food is dangerous? There are a lot of theories about this. One of the major drivers is the general sense that natural things are “good” while man-made things are somehow “bad.” There is just an irrational emotional reaction that many people have to the term GMO. People don’t realize that these conventions have basically no meaning when it comes to your food. Humans have been modifying the genes of the food we eat since agriculture began, and our successes in doing so are a major reason our civilization has been able to advance the way it has. One could make an argument that agriculture, and by extension civilization, requires genetic modification of our food. It is ironic that after all of this progress, and after the rise of modern civilization, that we humans would seek to get back to the “nature” that we have effectively been running away from for thousands of years.

It is difficult to change the narrative of GMO foods in the face of a culture set on labeling them as “bad,” but there is another major reason people fear GMOs that science can help with, and that improving education on the basic biology involved. Most people know enough to understand that DNA is important in defining what an organism is, but they don’t understand enough to know that adding a gene or even hundreds of genes could have no effect at all depending on where they are added to the genome, how these genes are expressed, and what they do.

You will hear people refer to “chemicals” in GMO food – and foods in general – with great concern, but this word doesn’t mean what they think it means in this situation. Amino acids are “chemicals,” so  is DNA, and literally every molecule in your body. All food is made of chemicals – actually 100% chemicals. You are made of 100% chemicals. Just because something is a “chemical” does not mean is it “bad.” You could classify chemicals as “natural” or “artificial” if you’d like, but one is not always better than the other. In fact, given that all the genes we introduce into plants are derived from other naturally occurring organisms and the proteins they encode are made by the plant, it would be fair to say that all of the chemicals in GMO foods are in fact “natural,” because a plant made them.  Some of the most poisonous substances known are “natural” – this  does not make them safe, nor are made-made chemicals inherently unsafe. For example: Hydrochloric acid seems like a scary chemical when it’s sitting on a bench in a beaker, but it’s also naturally produced in your stomach – which isn’t so scary – so which hydrochloric acid is more dangerous: the natural one or the unnatural one?

So let’s get back to our original question – are GMO foods safe? Yes, they are. You will find no accepted scientific evidence to say otherwise. This doesn’t mean you have to run out and eat GMOs every day. That’s your choice, and new labeling laws will make this choice much easier. It is only right that people are free to eat what they want, and if you or anyone else finds the concept of eating the product of a genetically modified organism unethical, or maybe just a little creepy, that’s cool. However, feeding into the narrative that GMO foods are unsafe or inherently “bad” isn’t doing anyone any favors. There are over 7 billion people on this earth, and we need GMOs to be able to feed all of them.

Saying GMOs are unsafe is no different than someone saying that vaccines cause autism, or that dinosaurs and humans co-existed. These are false statements – easily disproved by evidence. The next time someone tells you GMO foods are unsafe, do science a favor and correct them.