Different grades of olive oil help illustrate how processing can affect not only taste and antioxidant content but have important health implications as well. Extra-virgin comes from the first pressing and contains the largest amounts of polyphenols, which are an important source of antioxidants found in olive oil. Virgin oil, a lesser grade, comes from the second pressing. Pure olive oil is not pure at all. This is a still lower grade of olive oil that has been extracted using solvents and or heat which results in lower levels of polyphenols.

It is best to use extra virgin olive oil which is closest to its natural state and has the greatest amount of anti-oxidant polyphenols. Extra virgin olive oil is not only the best tasting grade but has demonstrated superior health benefits too. The better grades of olive oil, containing greater concentrations of anti-oxidant polyphenol compounds, are more effective in protecting LDL, bad cholesterol, from oxidation than lesser grades. LDL oxidation causes atherosclerotic plaques and lesions to develop and is thought to play an important role in the development of heart disease.

While chefs may tell you to use extra-virgin olive oil for salads and reserve less expensive oil for sautéing I would disagree. Sautéing meats with better grades of olive oil will also help reduce the formation of heterocyclic amines which are mutagenic compounds associated with increased rates of cancer. I use extra-virgin to sauté, in salads and as my general all purpose oil.