You know you're supposed to eat your veggies.
Produce is best when it's as fresh as possible.
If you can, get it from a local farm stand or your own garden. If you can't get fresh, frozen isn't as bad as you think. Usually, produce is frozen within hours of being picked, thereby preserving a lot of the nutrients. But while Popeye may get his spinach from a can, it usually contains salt, and the color and vitamin content is pretty low. Best to save the canned stuff for use in things like casseroles.