Which olive oil?

It is important that the olive oil you buy says on it "extra virgin" and "cold pressed". Extra virgin means it's the oil that comes out the first time the olives are crushed. Cold pressed means they didn't use heat to extract the oil (which they do for pretty much any other oil, especially the more processed ones). Both of these are important in order to get all the healthy nutrients from your olive oil. Yes, it's more expensive. I can't tell you what to do but I can tell you, it definitely is a worth while investment.