Rats were fed on raw and cooked genetically modified potatoes, using unmodified Desiree Red potatoes as controls
. One of the controls consited of an unmodified Desiree Red potato spiked with the GNA snowdrop lectin.
Twelve feeding experiments were conducted, ten short-term (10 days) and two long-term (110 days).
Before the experiment Pusztai and his team say they expected there to be no differences between the rats fed modified potatoes when compared to rats fed the non-modified ones.
Their experiment however showed a statistically significant
difference in the thickness of the stomach mucosa
. The mucosa of rats fed raw or cooked potato modified with the GNA gene was thicker than that of rats fed the unmodified potato.
length in the jejunum
was greater on rats fed the raw modified potato, although there was no statistical difference observed in the rats fed the cooked potato.
As these effects were not observed in rats fed the control potatoes spiked with GNA, Pusztai concluded that the differences were not due to the presence of GNA, but were a result of transformation procedure.
Stanley Ewen, who collaborated with Pusztai on the experiment, said that the use of the cauliflower mosaic virus
as a promoter
could be the likely cause of the changes observed.