There are constant claims made about GMO food safety – everything, from causing allergies to causing cancer. Taking lessons from the anti-vaccine world, anti-GMO activists invent, based on very little or even no evidence, various claims about GMO food safety. One of the worst of these claims is that when you eat GMO foods, the genes from the food somehow, by magic apparently, get incorporated into your genes.
In case you’ve ignored this area of pseudoscience controversy, genetically modified organisms (GMOs) are any type of organism where the genes have been modified by genetic engineering. Mostly, GMOs refer to agricultural crops, but there are other genetically modified foods, like salmon. To be clear, we have been genetically modifying food crops since the dawn of agriculture, over 10,000 years. However, we currently use GMO to explicitly mean genetic engineering in the modern sense.
Using the same anti-science arguments employed by climate change deniers, anti-GMO forces ignore the overwhelming scientific consensus, and use their pseudoscience to push concerns about GMO food safety. Let’s remember, the vast scientific evidence says that GMO foods are safe to humans, animals and the environment.
Unfortunately, like the zombie bad research on vaccines, a widely criticized article that seems to claim that DNA passes from GMO foods to humans continues to be an anti-GMO meme. Time to look at the article again, and see if gene transfer really is an issue to GMO food safety.
GMO food safety – the gene transfer paper
In a paper published in the online journal, PLoS One, the authors, Spisak et al., seem to indicate that there is a possibility that DNA fragments pass from the digestive tract into the blood. The authors concluded that:
…based on the analysis of over 1000 human samples from four independent studies, we report evidence that meal-derived DNA fragments which are large enough to carry complete genes can avoid degradation and through an unknown mechanism enter the human circulation system.
The authors admit that the mechanism is unknown, though it’s curious that years of study of the molecular transport of nutrients has never uncovered this until 2013. Based on this limited evidence, here’s what the anti-GMO crowd says about it:
What biotechnology and biotech corporations like Monsanto have done, is they have allowed for the transfer of genes from one to the other without any regard for the biological limitations, or constraints.
The problem with this is that it is based on very bad science. The conditions and biological ‘rules’ that apply to vertical gene transfer, at least those that we are aware of, do not necessarily apply to horizontal gene transfer.
Biotech science today is based on the assumption that the principles governing the inheritance of genes are the same when we move genes horizontally as they are when they are moved vertically. It just goes to show that GMO’s should be subjected to much more experimentation and rigorous research before we continue to consume them.
The paper’s conclusions were criticized by other scientists who are experts in DNA research. Moreover, there are some meta-level criticisms that can be made of this paper.
- This study is a primary publication that has not been confirmed by subsequent research. On the hierarchy of scientific evidence, primary research, especially if it’s not been repeated by others.
- Speaking of repeating this research, in the four years since this paper was published, only six papers have cited it, two of which criticized the quality of research. If this were truly groundbreaking research, we would see many more papers citing it, along with some research that repeats it.
- The study was published in an, open access, online journal, PLoS One, which has the publication philosophy of “publish first, judge later.” Well, we’re judging now.
- The study examine minuscule levels of DNA in blood, nanogram levels. We definitely are able to detect nanogram levels of DNA, but at that low level, substantial risk of contamination is so high, that if one were to see these results, the initial hypothesis would probably be “this blood sample was contaminated,” rather than the infinitely more complex and undiscovered mechanism to move these huge molecules into the blood.
- In fact, Richard W Lusk of the University of Michigan, spent six months reviewing the data and methods of Spisak et al. and concluded that they must consider contamination as the source of plant DNA. Lusk stated that contamination can account for these results, because DNA measurement is so sensitive, that even washed laboratory equipment harbors DNA fragments.
- In a review of the papers by Spisak et al. and Lusk, it was concluded that “Poor commentary and cherry-picking data helps no one. Spisak’s study tells us about a significant biological finding that needs to be carefully analysed. The cautionary tale is that one must not extrapolate wildly from good science to create horrific scenarios that are not based on any scientific observations whatsoever.” In other words, even if Spisak’s results were not affected by potential contamination, we still could not conclude that GMO food safety is impacted by this data. And given that it hasn’t been repeated, and we have firm evidence that there was contamination, this paper probably should not be used to evaluate GMO food safety.
As I have written, biological plausibility is an important factor in reviewing the viability of evidence in biomedical research. So let’s look at a few items about this research that seem to contradict what we know about biology:
- Based on our knowledge of the digestive process, fats, DNA, carbohydrates, and proteins are broken down into their simplest components, and specialized transport systems move these simple components across the barrier between the digestive tract and blood. Our digestive system has evolved to actually exclude full size bio-molecules, partially because the blood is incapable of carrying large foreign molecules (and could induce an immune response). So, a full chain of DNA isn’t going to move from the digestive tract to the blood, just individual nucleic acids. And just to be clear, nucleic acids are the same across every single organism on this planet. Exactly the same.
- Moreover, small constituent molecules, like amino acids instead of the whole protein, or glucose instead of a long-chain carbohydrate, are more easily transported to locations in the body to be then used as fuel or building blocks for new proteins and DNA. We just have not seen a mechanism in the digestive tract that can move large molecules, like gene-length DNA fragments, into the bloodstream.
- But let’s assume that there’s some unknown, mysterious mechanism that allows DNA to be transmitted into the blood (while excluding long chain carbohydrates, whole proteins, and other large molecules). The numbers are so small, just a handful complete genes, that the probability that those DNA molecules will have any effect on the body is near 0.
- Genes don’t easily jump from one species to another. If gene transfer were so simple, the medical usefulness of gene therapy would be extremely high, instead of being incredibly difficult, if not impossible. We’re trying to transfer genes to cure diseases, and researchers have not shown a lot of consistent success. If consuming a few kernels of corn, introduced some gene into the bloodstream that somehow gets incorporated into the human genome, well that would be a miracle. But reality is, even if the article is accurate, and there’s doubt to that, it has little clinical meaning.
- But the most important thing is that if there is some heretofore mysterious mechanism to transfer DNA from the digestive tract to the human genome, it should be noted that nearly everything we consume contains DNA. The plausibility that any number of DNA fragments from hamburger, salads, cereal, eggs, or the billion other foods will eat getting into the bloodstream is nearly non-existent. There is no evidence that we ever incorporate genes from corn. Or lettuce. Or a cow. Or a chicken. There is just no evidence of it.
- There’s actually evidence that contradicts Spisak et al. Researchers went looking for gene transfer in livestock that are fed GMO crops, and guess what they found? Nothing.
It’s not just that Spisak et al. represents faulty research, but it’s hard to comprehend how it’s even possible that DNA could be in a state that could allow it to be transported into some random cell of the body. This type of misuse of science is frustrating – anti-GMO radicals cherry pick research that seems to support their point of view, but fail to understand biology and physiology. Of course, this happens all the time with anti-science activists.
Summary, the TL;DR version
I don’t know if the study in PLoS One is going to stand the test of time given the high probability of contamination of the study samples, which has been demonstrated by another researcher. After four years, there’s just no further research that supports it, something that makes me think it’s a one-off study of marginal utility.
But even if it is confirmed by other research or becomes the initial observation that leads to the discovery of a novel, and implausible, mechanism of transport of nutrients and gene transfer, it provides NO evidence whatsoever that GMOs are dangerous because those genes will be incorporated into our human genome. GMO food safety concerns are unchanged because of this research.
You may as well become worried that we’ll turn into a chicken after eating an egg. Oh no. Franken-foods might cause franken-humans. And because…Monsanto.
- Lusk RW. Diverse and widespread contamination evident in the unmapped depths of high throughput sequencing data. PLoS One. 2014 Oct 29;9(10):e110808. doi: 10.1371/journal.pone.0110808. eCollection 2014. PubMed PMID: 25354084; PubMed Central PMCID: PMC4213012.
- Sharma R, Damgaard D, Alexander TW, Dugan ME, Aalhus JL, Stanford K, McAllister TA. Detection of transgenic and endogenous plant DNA in digesta and tissues of sheep and pigs fed Roundup Ready canola meal. J Agric Food Chem. 2006 Mar 8;54(5):1699-709. PubMed PMID: 16506822.
- Spisák S, Solymosi N, Ittzés P, Bodor A, Kondor D, Vattay G, Barták BK, Sipos F, Galamb O, Tulassay Z, Szállási Z, Rasmussen S, Sicheritz-Ponten T, Brunak S, Molnár B, Csabai I. Complete genes may pass from food to human blood. PLoS One. 2013 Jul 30;8(7):e69805. doi: 10.1371/journal.pone.0069805. Print 2013. PubMed PMID: 23936105; PubMed Central PMCID: PMC3728338.