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For the first time, it has
been proved that bacteria in the human gut can take up DNA from genetically
modified food.
Opponents of GM foods say the
results vindicate their warnings that this might happen, and that the
risk of gut bacteria scavenging antibiotic resistance genes from GM food
is no longer theoretical.
"This is a first,"
says Adrian Bebb of the Friends of the Earth. "We've said time and
time again there's a risk of this happening. Now, they've looked just
once and they've found it."
Burger
and Soy Shake
Harry Gilbert and colleagues
at the University of Newcastle upon Tyne made the discovery, after feeding
volunteers with a burger and a milk shake containing GM soya.
To see how the GM food was
dealt with by different parts of the digestive system, he gave the food
to 12 healthy volunteers and to seven volunteers who had previously had
their colons surgically removed.
When he examined stools from
the healthy volunteers, he found no traces whatever of DNA from the GM
food. It had all been digested. Nor did he find any evidence that gut
bacteria had taken up the DNA.
But when he examined waste
products collected from the seven ileostomy bags, he found that up to
3.7 per cent of the GM DNA survived.
Crucially, in three of the
seven, he found that bacteria had taken up GM DNA from the soya. But "despite
exhaustive attempts", he could not isolate the precise bacteria which
had taken up the GM DNA. He concludes that the DNA must have been taken
up only by tiny proportions of gut bacteria.
Destructive
Enzyme
To account for the differences
between the "ileostomists" and volunteers with intact digestive
systems, Gilbert's team speculate that DNA might survive the small bowel
but gets completely destroyed in the large bowel. They say in a draft
manuscript that people with ileostomies might produce less of the enzyme
that degrades DNA.
As supporting evidence, they
found that unmodified soya DNA survived in the small bowel as plentifully
as the GM DNA. "It shows that the GM DNA acts in the body the same
way as DNA from regular food," says a spokeswoman from the FSA.
In a separate experiment on
colonies of intestinal cells, Gilbert's team showed that raw loops of
GM DNA called plasmids can be taken up directly, but only by one gut cell
in 3000.
New
Scientist July 18, 2002
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