Hazards of Gene-Altered DNA
in Human Gut Underestimated

ISIS Report, 21 July 2002 (UK)
GM DNA in Human Gut Underestimated
By Dr. Mae Wan-Ho

UK's Food Standards Agency dismissed its new research findings that GM
DNA in food has transferred to bacteria in the human gut. Dr. Mae-Wan Ho
reveals how the experiment was designed to bias against positive
findings, so the actual transfer of GM DNA could be much more extensive.
There should now be a comprehensive ban on all GM crops, she says.

That GM DNA should transfer to bacteria in the human gut is not at all
unexpected. We already know that DNA persists in the gut, and that
bacteria can readily take up foreign DNA. Why did our regulators wait so
long to do the experiment? And an experiment that's designed against
making positive findings?

The research in question is the final part of the Food Standards Agency
(FSA) project on evaluating the risks of GMOs in human foods,
commissioned by the former Ministry of Agriculture, Fisheries and Food

A single meal containing GM soya was fed to human subjects. It consisted
of commercial soya meal - 150g El Corte Ingles, batch number and GM
content unspecified - mixed in the burgers and soya protein supplement -
100g Holland and Barrett, batch number and GM content again unspecified
- mixed in 'milk' shakes. No data were presented on how much DNA was
present in the commercial samples, and whether the DNA was broken down
and to what degree. Needless to say, the GM DNA inserts were not
characterised at all.

The method of detecting GM DNA is highly flawed. It depends on
amplifying a small part - 180bp - of the entire GM DNA insert that was
at least ten or twenty times as long. So, any other fragment of the
insert would not be detected, nor would a fragment that did not overlap
the whole 180bp amplified, or that had been rearranged. The chance of
getting a positive result is 5% at best, and likely to be much, much
less. Thus, a negative finding with this detection method most probably
does not indicate the absence of GM DNA.

More revealing still, the researchers checked for GM DNA only in the gut
contents, but failed to check if the DNA has passed through the gut into
the blood stream and blood cells. This omission is inexcusable, as a
series of experiments in mice dating back to 1997 had already documented
that GM DNA can pass through the gut wall into the bloodstream, to be
taken up by cells in the blood, liver and spleen. When fed to pregnant
mice, the GM DNA also passed through the placenta to be taken up by the
cells of the foetus and the newborn.

In the first trial, the GM meal was fed to seven subjects that had part
of their lower bowel removed from a previous operation and wearing a
colostomy bag. The digested food from the colostomy bag was analysed,
and GM DNA was detected in all seven subjects. As much as 3.7% of the GM
DNA was recovered in one subject. Bearing in mind the limitation of the
method used for detecting GM DNA, all the values are probably gross

In the second trial, the meal was fed to 12 human volunteers with intact
bowels. No GM DNA was detected in the faeces, which the researchers
claimed, indicated that the nucleic acid did not survive passage through
the complete intestine. But this claim is most likely to be false, due
to the limitation of the GM DNA detection method.

Microbes in the digested food that had passed through the small
intestine were cultured through 6 passages in broth containing
glyphosate. Bacteria grew to a density of 108/ml in each sub-culturing.
In each sub-culture derived from samples taken from 3 subjects at 180,
240 and 300 min after eating, the transgene was found. This is yet
another gross underestimate. The method depends on the bacteria having
taken up an intact gene coding for glyphosate tolerance, and would not
have detected bacteria that have taken up fragments of that gene, or
other parts of the GM DNA containing other genes or gene fragments.

Although GM DNA was not detected in samples taken from these 3 subjects
prior to GM soya consumption, when the microbes in this material were
cultured in broth containing glyphosate, the transgene was detected in a
sample collected before the GM meal, though at very low concentrations.
This suggests that the subject may already have GM DNA in the gut prior
to the experiment, possibly from consuming GM soya. The bacteria
harbouring the transgene could not be isolated, so the researchers
concluded that, "although present, the bacterium represented a very
small proportion of the indigenous intestinal microflora". But as
bacteria are capable of multiplying, even rare gene transfer events
cannot be ignored.

The researchers were disingenuous when they expressed surprise at the
relatively large proportion of GM soya DNA that has survived passage
through the small bowel. But in earlier research already published, the
same group had found that DNA in food or mixed up with food was much
slower to degrade than naked DNA.

Despite the severe limitations placed on detecting GM DNA, and an
experimental design both biased towards negative results, irrefutable
positive evidence was nevertheless obtained. That means the transfer of
GM DNA in the human gut could be much more extensive than the data
indicate. This makes it all the more astonishing for the FSA to have
reportedly claimed that "the findings had been assessed by several
Government experts who had ruled that humans were not at risk". Those
experts should now be named and made to defend their ruling.

In a statement on its website, the FSA said that the study had concluded
it is "extremely unlikely" that GM genes can end up in the gut of people
who eat them. This statement is highly misleading and very likely to be

Our government's scientific advisers have been guilty of persistent
denial in the face of mounting evidence that horizontal gene transfer
can happen and has happened. They are guilty of bad scientific research
that misleads the public, of downplaying positive evidence, and of
taking the absence of evidence as evidence of absence.

I first pointed out the dangers of horizontal gene transfer to MAFF in a
series of correspondence in 1996. Their scientific advisers said there
was no evidence it could happen. When it became clear that horizontal
transfer of GM DNA from GM plants to bacteria can readily happen in the
laboratory, the scientific advisors said "just because it happens in the
laboratory does not mean it will happen in the field". When positive
findings turned up in the only field monitoring experiment in the world
that has ever been performed, the scientific advisors dismissed that
too, and explained it away by a 'cautious' interpretation of the

This latest finding is the last piece of damning evidence that
horizontal transfer of GM DNA can indeed happen, has already been
happening, and cannot be controlled if GM crops continue to be released
to the environment. GM DNA, as opposed to natural DNA, is in many
respects optimised for horizontal gene transfer. Horizontal transfer of
GM DNA can create new viruses and bacteria that cause diseases, spread
drug and antibiotic resistance among pathogens, and trigger cancer by
jumping into genomes of mammalian cells. New 'pharm' crops are being
developed that poison our water and soil, affecting all organisms in our
food web. The ecological impacts are unthinkable. What more do we need
for an immediate comprehensive ban on GM crops?

If you wish to see the complete document with references, please
consider becoming a member or friend of ISIS. This article can be found
on the I-SIS website at http://www.i-sis.org.uk/

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