Is there a difference between grades of olive oil?

Q. Is there a difference between grades of olive oil? 

A: You really do get what you pay for with olive oil. Olive oil labeled extra-virgin indicates that the olives were pressed only once, extracting the richest flavors and including, what the industry calls, the “miscellaneous” ingredients that come naturally with it. These ingredients include antioxidants called polyphenols. Polyphenols stop LDL from oxidation (which is extremely damaging to the arteries). Downgrading to virgin or just plain old “olive oil” means the olives have been pressed a number of times, extracting bitter flavors. Chemical refining removes some of the polyphenols from processed olive oils even though they’re often labeled as "pure". Store your oil in an opaque container and in a cool, dark cabinet away from direct exposure to light and heat.