Q: I hear that you're not supposed to use olive oil when frying. Why is that, and what should I be using? I'm vegan, so you can hold the bacon grease—I know how you operate.
—Guessing on Grease
A: The frying-with-oil issue is a matter of the relative smoke points of various oils, i.e., the temperature at which different oils start to smoke.
Scientists have discovered a growing number of molecules, carcinogenic and otherwise toxic, that form when food is cooked at high heat. Heterocyclic amines, for example, are very nasty, and they form when meat is heated above 392 F. And even fry-pan vegans like yourself can worry about acrylamide, which is found in potato chips, roasted nuts and flaked breakfast cereals. Like heterocyclic amines, acrylamide forms only at high temperatures.
Generally when oil smokes, such bad molecules are created. Olive oil has a low smoke point relative to other oils, but as long as the oil isn't smoking, it's fine for frying. If your olive oil does begin to smoke, toss the oil, rinse the pan and start again. Low-temperature frying, or steaming, allows more of the nutrients in your food to survive the cooking process and make their way into your body.
If you're determined to fry high, safflower and grapeseed oils are my two favorites. Both have high smoke points, great flavor and are good for you. Peanut oil is good, too, if you want the peanut flavor. Canola oil is overrated and should be avoided. It's not a naturally clean oil and looks like tar before it's filtered. While the filtering helps, I prefer to use oil that starts clean.