Olive oil is good fat, and good for you. Douse your salads with it. Cook your vegetables in it. And take comfort in the knowledge that you're doing the right thing for your health, especially your heart health.
Not so fast.
While it's true the high content of monounsaturated fats in olive oil is better for your body than saturated fats from animal-derived products like butter, olive oil is not necessarily heart-healthy. Why? The clue is right there in the name: oil.
Oil, even the kind that's pressed from olives, is still fat. Fourteen grams of fat per tablespoon, in fact. And fat is rarely, if ever, good for your arteries [source: Novick]. Like other oils, olive oil has 120 calories per tablespoon, so calorie for calorie, it isn't even an ideal source of its other chief attribute: heart-healthy polyphenols. For example, crunching 55 calories worth of lettuce will net 150 milligrams of polyphenols. You'd need to eat 600 calories (or 5 tablespoons) worth of olive oil to gain the same effect. And olive oil doesn't offer additional vitamins and minerals the way lettuce does [source: Fuhrman].
Plus, if olive oil is heated to more than 400 degrees F or 205 degree C (the temperature at which would roast olive-coated vegetables) its fat molecules transform into trans fats, and those are definitely not good for your heart [source: Katz].
Bottom line: It's better to use olive oil instead of (not in addition to) other oils, but it should always be in moderation [source: Mayo Clinic].