There's really no affects at all. But that's only if it's within around a year or less of expiration date. It really depends on the food and how long it's been stored. If you open a can of mandarin Oranges after a few years, you can tell it's gone bad, because the can has a look like it's inflated, and when you open it, it releases a little liquid, squirting you. Dude, same affects as eating your every day moldy food. It's called bacteria making you sick.