If there is no apparent difference between a GE food and its natural counterpart, it is assumed to be safe according to present regulations. Only a limited set of characteristics needs to be compared. If this testing reveals no difference, the GE food is considered to be 'substantially equivalent'. Then no testing is required to make sure there are no harmful substances present which may appear unexpectedly due to GE. For more on this, visit PSRAST (Physicians and Scientists for the Responsible Application of Science and Technology).