"Pusztai and a colleague used potatoes that had been genetically modified to produce a protein, lectin. They found cell damage in the rats' stomachs, and in parts of their intestines."
The journal article they wrote can be found at:
http://www.gene.ch/genet/1999/Oct/msg00055.html
An excerpt: "In conclusion, the stimulatory effect of GNA-GM potatoes on the
stomach was mainly due to the expression of the GNA transgene in
the potato. By contrast, the potent proliferative effect of raw
GNA-GM potatoes on the jejunum, and the antiproliferative effect
of boiled transgenic potatoes on the caecum can be attributed
only partly to GNA gene expression. Other parts of the GM
construct, or the transformation, could have contributed to the
overall effects. Once bound, GNA is internalised by endocytosis;"
They have identified a link between GM potatoes and a bad side effect. However, they do not identify whether it is the recombinant gene that causes the problem, the synergy of the produced protein with other macromolecules or even if it could be a problem with the sampled rats.
I do not think this should translate to human nonconsumption.
1) The inability to determine the reason for the rat intestine degradation means there is no certainty that humans possess the same weakness.
2) The rats were fed a diet of potatoes + supplementary nutrition. Humans don't eat that. I refuse to believe this is a good indicator of human physiologic response.