Are GMOs carcinogenic?

In a recent debate in the comments of a YouTube video, I discovered something that is somewhat disturbing: A vast majority of people who claim that GMOs are carcinogenic don't actually know what "carcinogenic" means, and the evidence seems to indicate that they also don't know what "GMO" means either.  This includes at least one person who claims to have a degree in biology with a basic understanding of genetics (a claim that I do not believe).  Perhaps if I explain what these terms mean, it will help people to understand why it is absurd to claim that GMOs are carcinogenic.

The start with, what is a GMO?  Based on my experience, most lay people believe that a GMO is some kind of molecule or other thing that can be in their food.  GMO actually stands for Genetically Modified Organism.  An organism is something alive, like a plant, an animal, a bacteria, or pretty much anything else that is alive.  When we talk about GMOs in the context of food, we are generally talking about plants.  So ,GMO corns does not have GMOs in it, it is a GMO.  A GMO is merely an organism that has had its DNA changed in some way.  When we talk about GMO plants, we are generally talking about plants that had their DNA changed deliberately and directly by humans, but technically every plant, animal, and other living creature on Earth has arisen from millions of years of natural genetic modification, and a vast majority of the plants and animals that humans eat have had their genes deliberately changed though selective breeding.  Every GMO is just a regular organism that has had its DNA changed in some way that could have also happened naturally given the right conditions.

Creating GMOs is a complex process that does something simple.  There are several techniques for doing it, but there is one modern technique that is used for making pretty much all GMO food plants.  This technique starts by taking a plant with a specific desired trait and experimenting to figure out what gene in that plant causes the desired trait.  The most well known trait used in GMOs is resistance to a specific herbicide.  Another valuable trait might be more efficient nutrient use, which would be helpful in places with poor soil.  Once the gene is isolated, it is removed from the plant and injected into the cells of a plant that genetic engineers want to give the trait.  Genes can do a number of different things, but the most well known things genes can do is create proteins.  So a gene that makes a plant pesticide resistant might create proteins that break down the molecules of the pesticide before it can damage cells.  While it is theoretically possible that a gene from a plant could produce something that is toxic to humans, it is incredibly unlikely if that gene was taken from a plant that does not already product toxins that affect humans.

Now we should make sure we understand what "carcinogenic" actually means.  Google defines it as "having the potential to cause cancer."  It defines "carcinogen" as "a substance capable of causing cancer in living tissue."  Essentially, a carcinogen is a chemical compound or element that can pass into a cell membrane and damage the DNA inside the cell in ways that cause the cell to become cancerous.

So, what about GMOs being carcinogenic?  The first think to keep in mind is that technically carcinogens are compounds.  Compounds are molecules made up of atoms.  There are also a few carcinogenic elements, but they are rare in nature, so you don't generally find them without looking.  Nothing larger than a molecule can technically be carcinogenic itself, though we typically refer to objects containing carcinogenic molecules as carcinogenic themselves.  Technically though, it is not the tobacco itself that is carcinogenic, but rather it is the nicotine molecules (and a few other things) that are in the plant that are carcinogenic.  In theory, we could breed a strain of tobacco without nicotine (and the other things), and it would still be tobacco, but it would not be carcinogenic, because it does not contain any carcinogens.

Now, this brings us to GMOs.  The only way we can call GMOs carcinogenic is if they contain carcinogenic molecules.  Non-GMO corn does not contain any carcinogens, so it is not carcinogenic.  GMO corn cannot be inherently carcinogenic, because the genes we added are not carcinogenic (genes are just short pieces of DNA, and DNA is not carcinogenic, so genes cannot be).  What about the plant that we took the genes from, when we made the GMO corn?  Honestly, I cannot say, because I don't know what that plant was, but it is very unlikely any company would risk getting fined or shut down for knowingly taking such a risk, and since most plants don't contain carcinogens, it is safe to assume that if plants resistant to a particular herbicide exist, there are probably plenty of non-carcinogenic options.  (Keep in mind, these companies want your money, and if you die from cancer because their product is carcinogenic, they are not going to make as much money from you.)  Additionally, if a gene that is known to make a plant herbicide resistant is put into a non-carcinogenic plant, even if the original plant did produce carcinogenic compounds, the new GMO plant is extremely unlikely to produce carcinogens, because the genes that caused the original plant to produce them were not put into the new plant.  In fact, because most carcinogenic compounds produced by plants are fairly complex molecules, it is almost certain they are produced by a chain of processes, and reproducing the entire chain of processes in another plant would likely require a lot more than just one or two genes.  Making a non-carcinogenic plant produce carcinogens using genetic engineering would require deliberately doing lots of very expensive experiments to isolate all of potentially hundreds of genes involved in the process of producing that carcinogen, and there is no reason any for-profit company would spend that much money just to kill off its own customers.

To take this one step further though, there are a few processes that are far more likely to produce carcinogenic plants.  The first one produced pretty much every carcinogenic plant known to man, and that process is natural selection.  Tobacco was not invented by humans.  It evolved the ability to produce nicotine though natural selection (though humans did use selective breeding to increase its nicotine production, but Native Americans were smoking it in religious rituals long before that).  The second one, which is linked to natural selection, is radiation exposure, which can "damage" DNA.  This damage modifies the DNA in a much less predictable way than modern genetic modification techniques (and was actually used in early genetic engineering study).  This could cause a plant to produce carcinogens, but it would likely take hundreds or thousands of specific modification events for this to happen (and this is probably how tobacco evolved the ability to produce nicotine, over millions of years).  Given that a vast majority of plants on Earth don't produce carcinogens though (over millions of years of chances), it seems that the probability of millions of years of cosmic radiation resulting in a carcinogenic plant is also incredibly small.  Another process that is more likely to create a carcinogenic plant than genetic engineering is selective breeding.  Just the process of reproduction is rife with potential error.  Genes can get damaged, split and put back together wrong, or just end up with a bad combination.  This could create carcinogenic plants from non-carcinogenic plants, but again, after millions of years of evolution and thousands of years of deliberate selective breeding by humans, you would expect to see at least one food crop that produces carcinogens if this was at all likely.  So far, the only carcinogenic plants bred by humans appear to be the ones that we deliberately bred to produce carcinogens (like tobacco), and even those seem to have been made carcinogenic by nature long before humans discovered them.

What it comes down to is that GMOs are not inherently carcinogenic, and the modern processes used to make them would require deliberately spending millions of dollars and many years of work to make them carcinogenic.  No one with those resources is going to go to that much effort, especially not for-profit companies that have a vested interest in the survival of their customers.  Monsanto might be unethical, but they are not stupid.

Lastly, the FDA mandates that all GMOs be carefully tested for carcinogens.  They are also tested for other toxic compounds, though those are just as unlikely as carcinogenic compounds if both plants are not already toxic.  Note that the FDA does not require this testing for non-GMO plants, including plants produced using selective breeding, which means that there are good odds that GMO plants are actually safer than non-GMO plants.

If you want to stick to buying non-GMO foods because you don't want to support Monsanto and the way they abuse gene patents, fine.  That is a real thing, though perhaps not as bad as it used to be.  If you are buying into the claims that GMOs are carcinogenic or otherwise toxic though, you are wasting your money.  The only way any plant can be carcinogenic is if that plant produces carcinogenic compounds, and there is no evidence that any GMO does that, the probability of a GMO doing that without someone spending tons of money to make it do that on purpose is almost nothing, and even if they did, the mandatory and extensive testing required by the FDA would have found problems long before now.  The fact is, GMOs are not carcinogenic, and not even one carcinogenic GMO has been produced.  Don't waste your money on GMOs for your health, because it won't make any difference.  If you want to buy GMOs, do it because you don't want to support unethical companies, because otherwise you are not helping anyone.



(I should add, supposedly there is evidence that glyphosate,  the compound used in Monsanto's Roundup herbicide that the Roundup Ready line of GMO crops is used with, may be carcinogenic.  This does not make the crops carcinogenic themselves, though trace amounts of herbicide remaining on the crops could be hazardous.  It is important to realize that this is still better than the seriously toxic herbicides that were used before Roundup replaced them.  The best solution to this potential problem, however, is not to buy non-GMO foods that have probably been covered in those more dangerous herbicides.  The best solution is to wash your produce before eating it, something that has been recommended for over a century.)