OH NO IT ISN’T!
When food (or medical supplies for that matter) is irradiated, the gamma rays (which are a bit like X rays but have more energy) kill the bacteria. This makes the food last longer before going rotton or it sterilises the medical supplies. It cannot however make the food/supplies radioactive.
It’s like this…compare a radioactive source giving out gamma rays to a machine gun firing bullets at a target. The gamma rays damage the bacteria targets, the bullets damage the target. HOWEVER…after you have stopped firing your machine gun, there is absolutely no way that the target will start shooting out bullets!!! In the same way the atoms of the target food have absorbed the energy of the gamma rays and once the food is sitting on the shelf it will definitely not shoot gamma rays out again! (technical point: in fact when atoms absorb the energy of a gamma, they do re-emit a certain amount of it - another photon, however this happens almost immediately - it does not leave the atoms "loaded" and ready to fire at a later date)
So when someone hears that you have been to a nuclear power station visitor centre and says.."I thought so, you are glowing" they are only saying it through ignorance (but don’t scorn them…just explain patiently to them!)