How safe are GE foods? The honest answer is that nobody knows for sure. If you hear anyone saying GE foods are perfectly safe, they are lying. They don't know. GE foods are probably safe enough in the short term from a health viewpoint because, unknowingly, Americans have been eating them for several years and no epidemic has happened. But nobody knows - how can they? - what the effect on people eating these foods for ten or twenty years might be. Absence of evidence at such an early stage is not evidence of absence of risk. After all, it took some time for people to realise that tobacco killed about half of all smokers (and some non-smokers too). And the giant and rich tobacco corporations have fought against the clear and incontestable evidence tooth and nail. Why? 
Because they knew they would lose money! And they were right: people and governments have begun to sue them for the damage they caused. You don't die if you smoke one cigarette - but if people smoke thousands of cigarettes every year (as smokers do) for many years, every one in two will die at a much younger age than they should.
The companies claim to have tested the GMOs but in reality, only very few tests
have been done over very short periods on small laboratory animals like rats.
One man who set out to test a particular type of GE potato did come up with worrying
results and was promptly silenced. And one type of food produced by GE bacteria
may have even killed
people though nobody knows for sure.