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.
Conclusion
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/
Citations
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.
