With all the topics I could choose for the inaugural post in my new blog, I am a little surprised at my choice of topic. But then again, maybe this post epitomizes the blog’s very name, in that this topic is a bit “out-of-the-box” for me. You see, I respect the rather substantial scholarship regarding the safety of genetically engineered crops for human consumption. However, a good scientist always challenges herself/himself to remain open to new data that may conflict with one’s scientific understanding of an issue. And the paper discussed here does exactly that.
A paper in the journal, Small Ruminant Research, got my attention a couple of days ago. The title of the paper (paywalled, sorry) is Genetically modified soybean in a goat diet: Influence on kid performance, by Tudisco and colleagues. Since the paper raises concerns, I knew it was important to read it as soon as possible after learning of it.
Briefly, the experiment involved feeding four groups of goats (ten goats per group) a specified ration for 60 days before kidding. The four groups were fed a ration that contained either 13% or 20% (dry matter) of soybean meal that was either conventional or transgenic (glyphosate tolerance, MON40-3-2). A variety of measures were collected after kidding. Additional details are provided in the paper.
I am not an animal scientist, so I must be careful not to overstep my knowledge. However, the paper seems well-done in many respects. I see no reason to doubt the conclusions presented, though I welcome the comments of experts in the field.
Key conclusions were as follows, with commentary.
1. Tudisco and colleagues reported a “significant decrease in growth performances of kids from mothers fed genetically modified soybean, either 13 or 20% of the concentrate DM.” In animals fed transgenic soybean, they reported significantly lower protein and IgG antibodies in the colostrum, reduced protein and milkfat in the milk at 15 days (but not at later sampling times), and reduced IgG antibodies in the kids. To me, these were the conclusions that I found most attention-getting. I can postulate several possible explanations for these results (and there may be others):
a. Perhaps there was some nutritional difference between feeds for some parameter not measured in the study. This could be the result of the soybeans used not being isogenic, or not having been grown and stored under identical conditions. I would like to know more about the feeds used. How were they produced? What was their nutritional makeup? To their credit, the authors did provide some detail on nutrient composition, but I wonder if data on more parameters would be enlightening.
b. One could postulate a direct effect of glyphosate on animal health. This belongs on the list of possibilities, but the paper doesn’t clearly state whether or not glyphosate was applied to the glyphosate-tolerant crop, so this may not be a valid hypothesis for that reason alone.
c. Perhaps there was some effect on feed quality from the transgene itself, through some unknown effect on soybean metabolism. Again, this seems highly speculative and most unlikely, but in the interest of completeness, I include it.
d. Perhaps the recombinant DNA itself is harmful. In the previous item (1c), I was speculating that the transgene that might produce some unknown metabolic activity in the plant that was harmful to the consuming goat. In this item (1d), I am speculating that the recombinant DNA itself might be directly harmful. This is a long, long stretch, since federal agencies consider DNA to be non-toxic. Furthermore, Nature is the Master of DNA recombination in so many different ways. Recombinant DNA created by Nature abounds in our diet. (This will be the topic of one or more posts in the future). I know of no reason why recombination through lab manipulations creates chemical bonding that is somehow different or more dangerous than what Nature does all the time.
2. Tudisco and colleagues also reported that fragments of transgenic DNA were found in colostrum of the animals feed the transgenic soybean. This sounds rather shocking, but it isn’t to me, as I have seen several studies showing that dietary DNA can be found in trace amounts in mammalian blood and organs. This is true for transgenes as well as other DNA present in the foods we eat (see Forsman et al, 2003; Mazza et al, 2005; and Schubbert et al, 1997, cited below). To their credit, Tudisco and colleagues had the foresight to test for non-transgenic DNA in the colostrum, and they detected genes from plant chloroplasts (non-transgenic) and soybean lectin (non-transgenic). Again, the finding of transgenic DNA in colostrum may sound shocking, but based on the research I have seen, it is not unusual to find trace amounts of dietary DNA in blood and organs, whether the DNA is transgenic or not. In a previous study (Tudisco et al, 2006), the authors detected plant chloroplast DNA in the blood and organs of rabbits fed Roundup-Ready (transgenic) soybean meal. However, in contrast to the present study, they did not detect in the rabbits either the Roundup-Ready transgene or a soybean lectin gene. Both of these are present in soybeans at low copy numbers. In fact, to my knowledge, transgenes are always present in very low copy numbers in transgenic plants. This suggests that the probability of finding transgenic DNA in the bodies of mammals is lower than for dietary DNA present in high copy numbers, like the genes of chloroplasts or mitochondria. Continued research on this topic will be welcome, particularly research to evaluate whether transgenic DNA in the colostrum presents an unknown health risk. As of yet, I am unaware of evidence that transgenic DNA in the diet behaves any differently than nontransgenic DNA in the mammalian body, or that it poses a special risk as compare to nontransgenic DNA. I am open to credible data on this point but I have not yet seen them.
The negative growth effects reported in this paper certainly merit attention. It would be nice to know more about the feeds provided, but I am glad the manuscript was published, and I look forward to more research along these lines.
Ever since I first learned that traces of fragments of dietary DNA (transgenic or not) can be found in the blood and organs of mammalian bodies, I have wondered what, if any, is its health risk. The research described above suggests that if I have a nontransgenic apple for lunch, I would expect to be able to find DNA fragments from it in my blood serum and my organs a few hours later. Does this pose a risk? Has anyone ever done the research? What about the DNA fragments from the nontransgenic oatmeal and cranberries I routinely have for breakfast? Or the nontransgenic, homemade bean soup I had last night for dinner?
A Chinese researcher once asked me: if DNA in our food could somehow integrate into our own DNA, wouldn’t we find, in our own genetics, some gene fragments from rice, wheat, and other plants that humans have eaten for thousands of years?
I’ll close with this: I am always open to respectful exchanges that may provide me new insights and new scientific evidence on any topic of interest. My thinking is never “set in stone.”
Update 28 Oct 2015: It seems that the issue described in Point 1a above--that the effects observed may be due to some nutritional or physical difference in the feeds used--is worth repeating. Information I've seen since the original post highlights the challenges of assuring equivalent feeds in such a study. For example, here is a major regulatory body raising similar questions about another study: http://www.foodstandards.gov.au/consumer/gmfood/Pages/Response-to-Dr-Carman%27s-study.aspx.
Update 24 Dec 2015: These items in PubPeer recently came to my attention. I sought an independent opinion on these gel images from a top molecular biologist who, as a result of his evaluation, expressed high levels of concern (more like anger) about a number of the published gel images. Neither of us have conflict of interest to disclose with respect to any of the research presented here or the analyses posted at these links (which we did not author).
Update 26 Feb 2016: Please see the article at http://retractionwatch.com/2016/01/17/gmo-researcher-loses-paper-accused-of-manipulating-data/
1. Forsman et al, 2003. Uptake of amplifiable fragments of retrotransposon DNA from the human alimentary tract. Mol Gen Genomics 270: 362–368.
2. Mazza et al, 2005. Assessing the transfer of genetically modified DNA from feed to animal tissues. Transgenic Research 14:775–784
3. Schubbert, R., D. Renz, B. Schmitz, and W. Doerfler. 1997. Foreign (M13) DNA ingested by mice reaches peripheral leukocytes, spleen, and liver via the intestinal wall mucosa and can be covalently linked to mouse DNA. Proceedings of the National Academy of Sciences USA 94:961-966
4. Tudisco et al, 2006. Genetically modified soya bean in rabbit feeding: detection of DNA fragments and evaluation of metabolic effects by enzymatic analysis. Animal Science 82: 193–199.