How can we be sure that GM is safe?

After more than 15 years and many allegations, none of the myths about health problems resulting from GM consumption have held up to scientific scrutiny. The pre-marketing risk assessment goes far beyond all existing procedures applying to conventional food and makes GM foods the most studied foods we have ever eaten. 

In this risk evaluation procedure, both direct effects of the newly introduced proteins and DNA (such as toxicity and allerginicity), and indirect effects due to compositional changes (intended or unintended) are examined for each new GM event.  
In addition to this systematic assessment before marketing approval is given, post-market surveillance is organized via appropriate traceability and labelling measures, which are more stringent in the EU than anywhere else.