Cancer is a frightening prospect. Some time back, an in-law asked me what would be the most effective thing he could do to avoid dying of cancer. My answer was simple: stop taking your cholesterol medication. As sarcastic as that answer may sound, this is our reality: if you look at medical causes of death in aging adults, about half of us will die of cancer (all types combined) and half will die of heart disease. Heart disease used to be way ahead of cancer as a cause of death, but we have gotten much better at prevention and treatment for heart conditions and done not so well on cancer. Will you get cancer? I can't answer yes to that question for you in particular, but the average person had about a 50-50 chance right now, so it is reasonable to ask about things that may increase or decrease risk. In this context, I take your question to be specifically about GM crops.
So―do GM crops increase cancer risk? The short answer is no, and this is because of the process that is used to assess differences between GM crops and the conventional crop. This comparative safety assessment process, which is used in all international crop biotechnology assessment guidelines, is a method of identifying similarities and differences between the newly developed food or feed crop and a conventional counterpart that has a history of safe use. Every product goes through this assessment. Using this process it is necessary to understand DNA, RNA, resulting proteins and plant composition.
What about DNA, RNA or protein? Assuming that all three items are changed, there is DNA and RNA in every whole food that we eat―it is in virtually every cell in every plant, animal, yeast, fungus or bacteria that we consume, and we have a gut full of DNA and RNA in bacteria cells as well. DNA and RNA convey information using an essentially universal genetic code, and DNA and RNA undergo digestion in humans, and the component bases are recycled or used for energy production. DNA and RNA from food do not enter the human genome―period. If you stop to think about the biological chaos we would have if we picked up genetic material from our food, it is immediately obvious that life on earth as we know it simply could not exist if genes moved willy-nilly among higher organisms. While there is no question that mutations underlie cancer, it is also very clear that dietary DNA and RNA do not impact the human genome. We now sequence cancer DNA all the time, and there is not a single example of a human cancer dependent on DNA acquired from plants.
Protein is, of course, widespread in the human diet and is indeed essential for human nutrition. We can make our own DNA and RNA, but we can’t make all of the amino acids needed to make proteins. The proteins put into GM crops are digestible proteins. There are hundreds of digestible proteins in the human diet, and there are no examples of a digestible dietary protein increasing cancer risk. The bottom line—there is no reason for concern about dietary DNA, RNA or proteins and increased risk of cancer.
As far as compositional changes, we do know that plants normally contain a wide variety of chemical substances, some of which may increase cancer risk. This is true of all plants—both conventional and GM. We do not routinely measure these compounds in conventional crops. Studies have shown clearly that variability in composition of conventional plants, due to genetic differences among varieties and due to environmental factors, is considerably greater than the effects of inserting transgenes.
There has never been a credible study linking GMOs and cancer. The few studies that have made such claims have been soundly debunked by the international scientific community. Further, the FDA and other regulatory agencies around the world, in places like Europe and Asia, have reviewed these studies and found them not to be credible. The most recent and widely publicized study of GMOs and cancer was by Séralini and his colleagues in France. They said the purpose of the study was to determine whether feeding GM corn to SD rats over most of their lifetime would be harmful compared to rats consuming non-GM corn. Their findings did not show any significant differences, but some of the rats did develop tumors. The authors launched a media campaign to promote a link between GM corn and cancer. The expert community recognized quickly that Séralini and his colleagues had demonstrated the normal (admittedly impressive) tumor incidence in SD rats fed unrestricted diets. SD rats carry a genetic defect that results in very large numbers of tumors. There was no difference demonstrated between exposed and control animals, and the study may be the most widely rebutted study in recent times. Here is an extensive critique is from the European Food Safety Authority (EFSA)―but if you prefer not to read this extensive and detailed analysis, a brief review, with multiple links to independent agencies and scientific organizations who have rejected this study, can be found on Monsanto's website.
There are millions of different genes in the diet―over 30,000 in corn alone. None of these genes or the resulting RNAs or proteins have been subjected to long-term cancer testing, precisely because there is no biological basis for doing so. In the years that farmers have grown crops from GM seeds (since 1996), there has not been a single documented instance of human harm, including new allergic reactions to foods produced with them. We invite you to learn more in our "Explore the Basics" section.
The following resources discuss the health and safety of GMOs:
- A list of more than 600 scientific papers published in peer-reviewed journals that have evaluated the safety of foods derived from GM crops is available here.
- From 2001 to 2010, the European Commission funded more than 50 studies in Europe alone, at a cost of more than 200 million euros and performed by more than 400 research groups. These studies are summarized in A Decade of EU-Funded GMO Research.
- A list of organizations from around the world who have found that genetically modified crops are as safe as their conventional counterparts is available here.
- Information from the FDA regarding the health and safety of food derived from genetic engineering is available here.
- Information from Sense About Science, an independent trust in the U.K. that works with over 5,000 scientists to help the public make sense of claims about scientific evidence, is available here.