Olive oil is the principle fat source of the traditional Mediterranean diet, a diet that has been associated with a low incidence of some diseases, including coronary heart disease and osteoporosis. In addition to the main ingredient (ie. oleic acid) extra virgin olive oil also contains phenolic compounds, such as oleuropein- and ligstroside-aglycones and their derivatives. They are formed in olives by enzymatic removal of glucose from the polar parent compound oleuropein-glycoside. A Mediterranean diet rich in olive oil supplies 10 - 20 mg of phenols per day.