Knowledge of the presence of genetically modified organisms (GMOs) in our food supply is increasingly coming into the awareness of the American public. As this is happening, the question of the safety of ingesting genetically engineered (GE) products on a regular basis is often a concern. In truth, we’ve been consuming GE food products, often times unknowingly, for a period of 20 years.(4) It is estimated that 93% of all soybeans and 88% of all corn planted in 2012 were genetically engineered.(4) So, unless you’ve been extremely vigilant, you’ve been eating GMOs and you’ve probably been doing it for quite a while. But, before we get into the issue of safety, let’s back up a minute for those who aren’t aware of what GMOs are.
The Process of Genetic Engineering
Genetically modified organisms are produced by taking a gene from one plant or animal species and inserting it into another plant or animal species. Genes provide a map for organisms to make proteins. Proteins can serve various functions within a cell such as providing structure or movement within a cell, acting as enzymes (catalyzing chemical reactions) or as signaling molecules. The idea of genetic engineering is that by inserting new genes into an organism we can alter how that organism interacts with the environment by altering cellular functions. New genes can be added to plants for a number of reasons. They may improve drought resistance, alter nutrient content, produce natural pesticides or, most commonly, provide resistance to herbicides.
The Safety of Genetic Engineering
The current method of genetic engineering assumes that inserting one particular gene into an organism is going to lead to the production of one new protein by that organism. Unfortunately, this is not an accurate model of how living organisms work. Here’s why. The human genome contains about 20,000 to 25,000 protein-coding genes. In contrast, there may be up to 1 million different proteins in the human body. How can that be? This is possible because one gene can code for several different proteins. Therefore, the idea of inserting one gene and getting only one protein is very unlikely.
What does this mean? In theory, this means extra proteins of unknown function can arise from the process of genetic engineering in addition to the protein that was desired.(12) Even if one is certain of the safety of the engineered protein, one can’t be sure of the safety of various unknown proteins. This begs the question: are we looking for these extra proteins? Current comparative analysis between GMOs and conventional organisms is only completed regarding specific nutrients and chemicals (e.g., vitamin C, calcium, etc).(11) For example, the levels of vitamin C in conventional corn are compared to the levels of vitamin C in a GE variety and so on with other nutrients. If the GE variety of corn is found to be similar to conventional corn by these standards it is considered substantially equivalent.(11) By the idea of substantial equivalence, if a product is found comparable to its conventional counterpart, aside from the new gene and protein, then safety assessment should only focus on the new protein.(7) Therefore, the next step is to determine the safety of the engineered protein by assessing for risk of allergic or toxic reactions.(11)
But, does any of this answer the previously posed question? In short, no. This type of analysis does not look for rogue proteins. Certain types of analysis, such as proteomic or metabolomic analysis, can show the presence of these types of alterations. This type of analysis, however, is not currently very useful as it is difficult to interpret the findings due to the vast number of variables that can alter genetic expression – aside from genetic engineering – such as location, environmental conditions and year of cultivation.
One may like to assume that if the gene comes from a product that we already consume, it is unlikely that the gene will produce any proteins that would be harmful to humans. This is not an irrational assumption, though it is not necessarily an accurate one. Controls of gene expression occur largely outside the nucleus of a cell and are based on inherited properties of the organism (eg, in humans this could be environmental exposures of the parents, grandparents, etc) as well as the current environment of the organism. Therefore, assuming the expression of a gene will be the same from one organism to another, even if the gene is exactly the same, is not necessarily true. Additionally, because the gene insertion process is highly imprecise, a gene can very well be inserted into the middle of another gene leading to alterations in normal genetic expression.(2) Research has also shown that the gene insertion process can cause other kinds of mutations, such as rearrangement of genes at the insertion site, which could also lead to altered gene expression.(2)
A separate point of view asserts that because most proteins we consume are non-allergenic and completely safe, it is unlikely that a new protein is going to be problematic. After all, University of Nebraska-Lincoln’s AllergenOnline database reports that only 1,630 proteins (out of likely over a million possible proteins) are known to cause allergic reactions – less than 1%.(1) While this is true, it is somewhat misleading. True allergic reactions are known as a type I hypersensitivity response which involves the production of IgE antibodies to the offending substance. There are, however, other types of hypersensitivity responses and autoimmune reactions that can occur to proteins – some of which are still not well understood.
