Sunday, November 3, 2013

GMO DNA and your health

I'm behind on my blog: I've been on vacation. My new job also has a longer commute time, so I've been falling asleep in front of the TV every night, instead of diligently reading papers. Someone
should really start working on that teleporter.

A reoccurring statement that I've read time and time again on anti-GMO webpages is about the dangers of eating GMO DNA. I've always just glossed over these claims, because they seemed a bit too science-fiction-y. But before I proceed, a voice in my head (which sounds like my husband's) is reminding me to give a bit of an intro on why I've glossed over these claims. Here are my top two reasons:
  • Nearly every cell-type in the body of every living creature has DNA. Whether that cell is from the organic beef of a cow or a pesticide-infested fruit, they all have DNA. And your digestive system does not know the difference between the two. So if GMO DNA is going to "sneak into your body", so will the DNA of that delicious bacon you ate this morning. As well as the DNA from those pork-chops. And ham. (Those are all from the same animal you say? That's preposterous!)
  • Even if DNA from your food got into your body, then what? The DNA would have to hijack your body's cellular processes in order for anything to happen, similar to how a virus operates. 

So that's why I've ignored these statements, which really seemed like fear mongering when I read them. However, I've read a few articles that claim that the DNA doesn't necessarily have to transfer into you. It might just transfer into the healthy-bacteria that lives in your gut. Due to this possibility, I decided to look into matters. In fact, taking a look at the Institute for Responsible Technology's section on "Health Risks", there's a whole section on "Functioning GM genes remain inside you".

The most commonly cited paper tied to these statements is from a  2004 Nature publication entitled "Assessing the survival of transgenic plant DNA in the human gastrointestinal tract". Apparently, the publication of this paper was quite the coup for the anti-GMO field. The paper looks at the survival of GMO DNA in the intestinal tract, because in order for the DNA of a GMO to transfer into bacteria from the gut, then it has to survive the digestive process. The authors looked at DNA from GMO soy and native soy, in ileostomists (basically, individuals who do not have a lower intestine) and individuals with intact digestive systems. Here's the summary:
  • GM soy and regular soy were fed to participants. DNA from soy and GM soy was detected in the "digesta" of the ileostomists, but it was not detected in regular individuals. The authors conclude that the DNA can survive in the upper intestine, but not lower intestine.
  • GM soy and regular soy DNA were degraded at similar rates.
  • The authors identified fragments of GM soy DNA in bacteria from the intestinal flora in ileostomists at very low concentrations (probably existed before the study started). The authors were unable to isolate the bacteria. Additionally, they were unable to reproduce this experiment in individuals with intact digestive systems.
I'd like to take the liberty of copying the conclusion from this paper (my clarifications are in brackets): "In conclusion, we have shown that a small proportion of the transgenes [GM DNA] in GM soya, like the native soya DNA, survives passage through the human upper gastrointestinal tract but is completely degraded in the large intestine. Although we found some evidence of preexisting gene transfer between the GM soya and the human small intestinal microflora, the bacteria containing the transgene represented a very small proportion of the microbial population, and there was no indication that the complete transgene [full gene from the GMO] had been transferred to the prokaryotes [bacteria]. Thus, it is highly unlikely that the gene transfer events seen in this study would alter gastrointestinal function or pose a risk to human health. Nevertheless, the observed survival of transgenic DNA from a GM plant during passage through the small intestine should be considered in future safety assessments of GM foods."

Note the sentence that I highlighted. Contrast this with the health risk from the Institute for Responsible Technology's webpage that refers to this paper: "The only published human feeding experiment revealed that the genetic material inserted into GM soy transfers into bacteria living inside our intestines and continues to function. This means that long after we stop eating GM foods, we may still have their GM proteins produced continuously inside us." For the first time in this blog's history, I will use the phrase: 'that is a blatant lie'. First of all, the genetic material wasn't found in bacteria of individuals with intact digestive systems (i.e. the overwhelming majority of people on the planet). Second, the whole gene was never found in bacteria, which makes it impossible for an intact protein to be produced, much less for that protein to "function".  #EpicFail #IRT

The next three statements on the IRT's webpage are:
  • "If the antibiotic gene inserted into most GM crops were to transfer, it could create super diseases, resistant to antibiotics.
  • If the gene that creates Bt-toxin in GM corn were to transfer, it might turn our intestinal bacteria into living pesticide factories.
  • Animal studies show that DNA in food can travel into organs throughout the body, even into the fetus."
Let's start with the first two statements. Note that there's no evidence for them, they're "if" statements. Let me make a few "if" statements:
Do I have any evidence? Well, I provided a few links and citations there, didn't I? And they're all to legitimate sources. Note that that is more evidence than the IRT provided for their two hypothetical scenarios.

There's one final statement: "Animal studies show that DNA in food can travel into organs throughout the body, even into the fetus." This is tied to a slew of articles and a quick scan through the titles and abstracts indicates that it's accurate. However, as I pointed out earlier, "then what"? DNA in food can travel into organs throughout the body, even into the fetus, whether that DNA is GMO or not. So DNA from our food has been circulating through our systems ever since we started eating.

If your argument is "Mother Nature never intended for us to eat foreign DNA", then what about when you eat a broccoflower? Or a pluot? In fact, if you eat any fruit or vegetable that is exotic, then Mother Nature never intended for you to ingest the DNA from that plant. For example, if you're Northern European and you eat a banana, or a mango, or a dragon fruit, isn't that DNA foreign to your system?

There's one final argument in my head that puts a nail in the coffin of this whole deal: humans aren't the only species that have bacteria in their gut. Mammals have been eating plants for millions of years. If any sort of absorption of genetic material were to happen between gut bacteria and plants, wouldn't it have happened by now? We've been part of this "human feeding experiment" ever since mammals starting eating plants, and even birds and fish before that (birds also have bacteria in their guts, as do little Nemos). If you consider that the most abundant protein on the planet is thought to be RuBisCO (a plant protein), then throughout the course of evolution, the bacteria in the gut of some animal would have taken up RuBisCO DNA. But that has not been identified (however, my husband wisely points out that this may have been the origin of the Ents in LOTR).

There are dozens of papers that have looked at the absorption of DNA in our food. All of them have the same conclusions: DNA from our food behaves the same, whether its GMO or not. Our digestive system breaks down the vast majority of the DNA (although this paper did find that complete genes may make their way through, but I reiterate: then what?). That DNA can be detected in feces and our organs.

Well, that's all I've got. If you have any questions, please comment below.

2 comments:

  1. My question is why is all of this secrecy demanded by the chemical companies who support genetically modifying our foods and oppose at all cost labeling it? Why are they so scared to tell us what we are buying? Why do they get to decide what I buy and not me?

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    Replies
    1. I think companies have good reasons to oppose labeling, primarily because survey after survey, we've seen that the public isn't well informed about GMOs. As such, a label conveys the idea that GMOs are dangerous and need to be labeled.

      I'd like to discuss this with you further. What aspect of GMOs do you think should be labeled? The variety of GMO used? Or just a generic label on the package stating "may contain GMOs"?

      Also, if you want to avoid GMOs, the USDA already offers the "certified organic" label which excludes GMOs.

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