Historically the Mediterranean countries have had low incidences of chronic diseases in sharp contrast to other countries. Researchers have focused on diet as a specific cause, specifically the traditional Mediterranean Diet with its reliance on olive oil as the main fat.
Extra virgin olive oil is primarily a monounsaturated fat which was believed to be the reason it was so healthy. However, research in the last twenty years has zeroed in on the small plant chemicals, known as the phenolic content of extra virgin olive oil. These phenolic compounds are small, numerous, and potent for health. These phenolic compounds vary widely and include flavonoids, lignans, sterols, phytosterols, and particular phenols unique to extra virgin olive oil such as oleocanthal, hydroxytrosol, and oleuropein.
These phenolic compounds also help keep the olive oil stable and are an indicator of EVOO quality. These complex phenolic compounds have been reported to have antioxidant properties based on numerous peer-reviewed studies.
The phenolic content of olive oils varies according to the climatic conditions in the producing area, when the olives are harvested and how ripe they are when picked. Oil production and storage methods also have an influence.