So What Is the Evidence?
Studies so far suggest there is no problem:
1. One experiment has been done on seven human volunteers
who had surgery in which the last section of the small intestine
had to be removed, with the contents diverted into a collection
bag. When they ate food that had a gene in it for herbicide
resistance, all subjects showed a maximum of 3.7% or less of the
gene had survived. This suggests that stomach and small
intestine digestive juices destroyed most of the gene.
2. When the same food was eaten by
volunteers who had complete digestive tracts, NO trace of the
gene appeared in the feces. This suggests that the microbes in
the large intestine complete the destruction of any remnants of
the gene that survive the small intestine.
HOWEVER: it is possible for genetic change to
occur in insects that feed on genetically engineered plants -
this may have happened in monarch butterflies.
here for more.