People still don't seem to fully grasp the whole 'whole food' concept. It's funny. Someone actually asked me "But, I mean you can eat Pringles, right?"
We have been so engrained (forgive the pun) in this culture to not even recognize the difference between whole and processed... healthy and not-so healthy.
I've narrowed it down to three basic overall rules of thumb when trying to eat your healthiest:
1. If you don't recognize the ingredients... chances are good that your body won't either.
2. If it has ingredients listed anywhere on it... chances are good that it's not a whole food item.
3. If it doesn't go bad... chances are good that it isn't good to start with.
Hope this helps.
And that you keep these guidelines in mind next time you go to the market.
... Which actually brings to mind a fourth rule of thumb:
4. If it's found in an aisle at the grocery store... chances are good that it's not a healthy item.