28 Oct 1999
Genuine gene squabble
By publishing a scientific report that even its reviewers questioned, a
British medical journal has put the question of the safety of genetically
modified food squarely on the table. 
These foods are made by moving foreign
genes into foods. Millions of acres of corn, soybeans and potatoes are being
planted with genetically engineered seeds, and while they have been accepted
in the United States, they are meeting considerable opposition in Europe.
Now comes word that potatoes which received a gene for a natural pesticide caused abnormal growth in experimental rats. The pesticide in question is not the one found in the genetically modified seeds on the market, which contain Bacillus thuringiensis, a pesticide normally made by a bacterium. The new study, reported in Lancet on October 16 (1999), concerned the plant-derived pesticide lectin, which comes from snowdrops, an early-spring bulb with white flowers.
Spud gun
Before we get to the delicious scientific dispute over the study, which the
prestigious medical journal considered for 18 months, let's look at what
researchers Stanley Ewen, a pathologist at the University of Aberdeen
(Scotland), and Arpad Pustzai, formerly of the Rowett Research Institute in
Scotland, did.
The researchers fed potatoes that carried a gene from the snowdrop that
caused the spuds to make lectin. In nature, lectin helps protect snowdrops
from insects, and theoretically the gene could also help protect other plants.
The researchers fed groups of rats one of these menus: lectin-boosted
potatoes, regular potatoes, or regular potatoes plus lectin from a bottle.
The diet must have been a trifle boring; as best we can tell from the report, the rats ate nothing but spuds. Some even ate them raw... None died of boredom, but when, after 10 days of this tedium, the researchers put the rats out of their misery and studied their intestinal tracts, here's what they found:
Intestinal fortitude
Eating lectin -- whether it came from the transferred gene or was simply added to the diet -- was associated with a thickening of the mucus membrane lining the stomach.
In short, eating genetically engineered potatoes caused some cells to grow, and others to fail to grow, in the stomach and intestine. The researchers pinned some of these effects on the foreign gene. They said others could be due to the process of genetic engineering itself. If that's true, then the technique might also be suspect when used to move other genes.
Did someone say suspect?
Suspect is exactly how some scientists saw the report. Even after three
rewrites, Lancet's editorial team was divided about publishing it, and the
same issue ran a sort of apology from the editor, saying, in effect, "There,
we published it. You can't accuse us of a cover-up, but we're not convinced
it's right."
A commentary in the issue, by Harry Kuiper of the National Institute for Quality Control in Agriculture Products at Wagengin University in the Netherlands, raised some specific shortcomings in the research:
However, in an e-mail interview, Ewen responded to these arguments. "The
question of control groups is straightforward. The best control" is the rats
that ate non-modified potatoes. "The rats were not ideally nourished on the
raw potatoes but did not lose weight. The effects of starvation is exactly the
opposite of what we see in the crypts. Starvation causes atrophy [shrinkage]
of crypt length at 48 hours of starvation and what we see is a significant
lengthening of crypts."
Stephen Taylor, a toxicologist at the University of Nebraska at Lincoln, who has studied allergic reactions to transgenic foods, noted some other problems: "I understand that it's hard to decipher exactly what the experimenters did. That's unforgivable. The first thing you learn in graduate school is that you write up your research results in such a way that another person could repeat your experiment."
Taylor also questioned the experimental technique: even if the lectin was toxic - and there are indications that it can be -- "It's highly unlikely that it would be so toxic as to make the animal sick when you feed whole potatoes." Rather, Taylor says, it's better to feed animals concentrated doses of potential toxins, much as cancer researchers do.
Nevertheless, it seems that the long-awaited Ewen-Pustzai report will force
more attention on the issue of food safety. For his part, Ewen expresses
concern that he was not able to continue the experiments. "We had several
planned experiments ready to roll but then officialdom took over and the
establishment closed us down."
-- David Tenenbaum
Bibliography
Effects of Diets Containing Genetically Modified Potatoes Expressing Galanthus
Nivalis Lectins on Rat Small Intestine, Stanley Ewen and Arpad Pustzai, The
Lancet, Oct. 16, 1999, pp. 1353-4 (see also commentaries on pp. 1313-15).
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