As was stated above, publications on GMO food toxicity are scarce, except for studies using animals only. In fact, no publications of clinical studies on the human health effects of GMO foods exist.
A few investigations using rats have revealed that GMO foods might cause some effects, as bacteria do become resistant to antibiotics, production of some allergies and a decrease in the ability to digest.
Nevertheless, any carcinogenic effect of GMO foods on humans has not been proven yet.