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 rats that ate only raw genetically modified potato, the crypts were longer in the middle section of the small intestine. Dejargonation station: Crypts are tiny pits that secrete mucus into the intestine. Mucus keeps the partly digested food moving and increases absorption.

Eating transgenic potatoes was also associated with fewer lymphocytes - white blood cells that help in the immune reaction - compared to eating normal potatoes.

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:

Too few rats -- only six per food type -- were used.

All the rats ate a lousy diet -- pure potatoes, which contains only 6 percent protein, far less than the 15 percent found in standard lab rat chow. "There is convincing evidence that short-term protein stress and starvation impair the growth rate, development, hepatic [liver] metabolism and immune function of rats," Kuiper wrote. And we note that the rats didn't even get French fries, either...

There was no control group -- no group of rats ate a good rat diet for comparison.

Finally, Kuiper maintained, "no consistent patterns of changes were observed" during the study.

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