Olive oil has been part of human diets and has been used for medicinal purposes since ancient times. Spain is at the forefront of the global ranking of countries producing olive oil. Olive oil contains a high proportion of monounsaturated fatty acids (MUFA). Phenolic content in olive oil depends on the variety of olive fruit, region where it is grown, climate, agricultural techniques used, maturity of the olive fruit at harvest, and olive oil extraction, processing, storage methods, and time since harvest.