Why Worry About GMO Safety?
To tie into Michael’s post from yesterday, and also a recent conversation with a friend, I want to write today about GMO safety. This is an issue that I first learnt about when studying biology back in the 1990s at university. I worked with bacteria modified by genetic engineering techniques from 2005-2007. Since writing for TalkingNutrition, I have also been brought into contact with consumer concerns about GMOs in food. Many times when I read articles about the safety concerns of GMOs, I wish that the author could pick up a biology textbook and think critically about whether what they are writing makes sense. This is echoed by the results of a fairly recent consumer survey that showed a similar percentage of US adults support the labelling of food containing DNA as support the labeling of foods containing GMOs.
I am personally not concerned about the safety of GMOs. This is due to several fundamental concepts about genetics that are common knowledge, which I would like to share with you today.
We Come into Contact with DNA from Thousands of Organisms Every Day
DNA is in all living cells. DNA remains at least partially intact even if the cells are no longer living, or are processed. DNA is also present in bacteria and fungi that are part of our personal microflora and in the environments that we live in. This means that we eat, breathe and produce “foreign” DNA all the time. When we eat an apple, or a slice of bread, or almost any other food with the exception of highly processed cooking oils, salt or sugar, we are eating DNA from these organisms. Bacteria in the large intestine from hundreds of different species produce DNA, and this is exposed to our mucous membranes when the bacteria split apart as part of normal turnover in the gut. This process is understood to be an essential part of the immune system (Canny and McCormick). We have bacteria and fungi living on our skin, and we breathe them in with every breath. We are constantly exposed to DNA from other organisms.
All Living Organisms Share DNA
Ever heard that human and chimpanzee DNA is 98% the same? How about that a quarter of the DNA of humans and rice plants is identical? We share DNA not only with plants and animals, but also with fungi and bacteria, because the same cellular processes are present in all forms of life. The human genome is not a discrete unit: rather, it is a basic framework that has many similarities with very similar organisms, and fewer similarities with organisms that are largely different to humans. While people like to talk about examples like a gene from a fish being inserted into a tomato to produce a GMO, the reality is much more fuzzy. Tomatoes and fish already share a lot of DNA. The particular gene that is transferred is just one more gene that is the same along with the other thousands that are shared between these two life forms.
Genetic Variation Is Everywhere
I have two children. My son has dark hair like me, and my daughter is blonde like her father. Hair color is genetically determined but the relationship between genes and hair color is complex. An important gene in determining hair color is the MC1R gene, which codes for a protein that regulates the production of pigment for the hair (and skin). There are more than 30 genetic variants in this gene found in humans that are linked to hair color. If the protein is working well, hair is dark, but the variations in this gene that result in a loss in function result in a lighter hair color. The exact combination of the two genetic variants (one from each parent) determines a child’s hair color. Interestingly, this gene is also found in other species: our cousins the chimpanzee, our best friend the dog (and cat), our lab friends the rat and mouse, the Colonel’s friend the chicken, and also our hairless friends the zebrafish and frog. In fact, we have found over 100 other species that have the same gene.
My point with this section is to show that there is a wide variety of genetic variants for each gene, and while these small differences result different characteristics, such as different hair color in my two children, organisms thrive despite differences in their genetic code. I think this example also illustrates the genetic similarities between species.
How Does This Relate to GMO Safety?
Some people who are against GMOs cite safety concerns. For example, the Center for Responsible Technology cites concerns that genes inserted into GM soy transferred to the human microflora, that the genes transferred to “unrelated” organisms will escape and “contaminate our gene pool”, and that there is “collateral damage” from genetic engineering processes that will create toxins, allergens and nutritional deficiencies. These concerns echo those that I have been reading over the years.
I am not worried about genes from GM foods that I eat transferring to the microorganisms that are part of my microbiome. If a gene from GM soy can transfer to my gut bacteria, so can the genes from all the other foods that I eat. I am not concerned with all those genes, so why would I worry about the single gene from GM soy? It is a modified version of an enzyme that plants and bacteria use to produce amino acids – the modification means that it is less affected by the herbicide glyphosate than the “normal” gene.
I am not worried about genes “escaping” and the gene pool being contaminated by GM genes. This concern is particularly strange especially considering that conventional breeding techniques that include the use of mutagens to produce new mutations, and the intentional selection of cultivars or breeding stock that has a faster growth rate than wild organisms is apparently not a concern. The genes in GMOs are those that are found in other organisms and are already present in the environment.
I am not worried about collateral damage caused by inserting genes into other organisms. If damage to the genome does occur due to genetic engineering, the most likely result is that the organism will fail to grow in the lab. Current safety testing of GMOs is sufficient to ensure that unexpected toxins and allergens are not created. Genetic engineering is actually a way to improve the nutrient content of foods (Farre). GM foods are nutritionally equivalent to their non-GM counterparts (see EFSA report).
DNA is everywhere. All organisms are related, but there is considerable variation in genes even in closely related individuals. Use commonsense when thinking about the safety of foods produced by genetic engineering.
Geraldine O. Canny and Beth A. McCormick. Bacteria in the Intestine, Helpful Residents or Enemies from Within? Infect. Immun. August 2008 76:8 3360-3373; Accepted manuscript posted online 12 May 2008, doi:10.1128/IAI.00187-08
EFSA GMO Panel Working Group on Animal Feeding Trials. Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials. Food Chem Toxicol. 2008 Mar;46 Suppl 1:S2-70. doi: 10.1016/j.fct.2008.02.008. Epub 2008 Feb 13. http://www.ncbi.nlm.nih.gov/pubmed/18328408
Farré G, Bai C, Twyman RM, Capell T, Christou P, Zhu C. Nutritious crops producing multiple carotenoids--a metabolic balancing act. Trends Plant Sci. 2011 Oct;16(10):532-40. doi: 10.1016/j.tplants.2011.08.001. Epub 2011 Sep 6. http://www.ncbi.nlm.nih.gov/pubmed/21900035
Richard Dawkins. The Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution. Mariner Books. ISBN13: 9780618619160