Olive oil is an essential ingredient of the Mediterranean diet. Olives have been grown and harvested in the Mediterranean for thousands of years to make olive oil, and Spain, Italy, Greece, and Tunisia are still the top producers in the world. In ancient times, it was an extremely important commodity; in addition to its value for cooking, it was used to fuel oil lamps, as a base for perfume, and for medicine. Olive oil has also long been recognized as part of a healthy diet. 

Starting in the 1990s, Oldways helped popularize olive oil outside of the Mediterranean through a series of scientific conferences, cultural and culinary symposia in Mediterranean countries, and other Mediterranean Diet educational programs. One important program focused on the scientific consensus around dietary fat, concluding -- at a time when low-fat mania reigned -- that a moderate fat diet was best for disease prevention and weight control. The Mediterranean diet uses a fair amount of fat, but it mostly comes in the form of plant-based unsaturated fats like olive oil, fats that are associated with a lower risk of inflammation, heart disease, diabetes, stroke, and cancer. 

Almost everywhere you can use butter in your cooking, you can use extra virgin olive oil. It can be drizzled on salads, heated in the pan, and used in baked goods. Many of the aromatic compounds that give premium oils their distinctive flavors evaporate into the air during cooking, so it's a good idea to keep a variety of olive oils in the pantry - inexpensive olive oil for frying, an EVOO for cooking and baking, and pricier EVOOs for drizzling. Age also matters; a traditional practice is to use last year's oil for cooking and this year's oil for drizzling.

The four foes of olive oil are age, heat, air, and light. When you buy olive oil, make sure it is no more than 18 months old (look at the bottling date on the label). At home, store it in a cool, dark place.