Some people might say that cooking with extra virgin olive oil at high heat is not good for you. However, looking at the studies, olive oil's main health benefit is its fat composition. Olive oil is mostly monounsaturated fat. Cooking with an oil will not change its fat composition. Olive oil's percentage of monounsaturated fat remains the same after heating, even to high temperatures.
The North American Olive Oil Association talks about heat and cooking with olive oils. The major points around this topic include:
Smoke point - All oils will become unhealthy if heated past the smoke point. Stovetop cooking is usually around 350ºF. The smoke point of extra virgin olive oil is 350 - 410°F and the smoke point of olive oil or light-tasting olive oil is 390 - 468°F. There is a difference between cooking and burning your oils and foods. You can burn both, but if you stick to conventional cooking methods, and focus on bringing out the flavor in your food, rather than burning your food, you should enjoy a healthy and delicious meal.
Carcinogens or other toxic compounds - Heating any oil past its smoke point will produce toxic compounds. Fortunately, olive oil contains phenols and antioxidants that prevent it from creating toxic compounds when heated. In 2004, a team studied the aldehydes produced by heating extra virgin olive oil, olive oil and canola oil to 464°F. The study found that both extra virgin and regular olive oil were healthier than canola oil. Read more
Oxidation - Olive oil has been scientifically proven to resist oxidation when heated, not the same with unsaturated fats. Polyunsaturated oils (such as Canola) are significantly more likely to oxidize over the monounsaturated fats (found in olive oil). Read more
Phenols - We have heard that you should not cook with olive oil because the phenols will be destroyed by the heat. It is true that phenols in olive oil are sensitive to heat. However, a recent study made a remarkable discovery. When cooking with extra virgin olive oil, the phenols move into the food. Potatoes fried in EVOO contained more phenols and antioxidants than potatoes boiled in water. Read more.
What might change with prolonged heating with olive oil -Heating olive oil does not damage the health benefits but it will make the olive oil lose some flavor. When choosing your olive oils to cook with, consider a more robust oil for cooking. And, if you have a newly harvested extra virgin olive oil with complex flavors, you may want to focus its use on finishing or salads, or other cold uses like dipping a fine bread.
Basically, olive oil is safe and healthy – even when cooking with it. Using conventional cooking methods will not effect the health benefits of extra virgin olive oil. Experiment with your olive oils and your recipes. Test the difference yourself in the flavor profiles of the oils with your meals.