It is well established that food is not considered to be mere nutritional components for maintaining human life. There are a broad number of studies reporting that many foods may provide a health benefit beyond basic nutrition. Within this context, extra virgin olive oil (EVOO) has been related to the prevention of some types of cancers and the reduced risk of coronary heart diseases. This is mainly due to its high concentration of a broad variety of phenolic compounds, such as phenyl ethyl alcohols (tyrosol, hydroxytyrosol), phenolic acids (4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, gallic acid, vanillic acid, ferulic acid, caffeic acid), flavonoids (apigenin, luteolin), secoiridoids (oleuropein and ligstroside aglycons) and lignans [(+)-pinoresinol, (+)-acetoxypinoresinol)]. In the human organism these polyphenols are metabolized and form different compounds. Thus the study of their properties is highly important with regards to understanding their functionality. The aglycones can be absorbed from the mall intestine; however, most polyphenols are in the form of esters, glycosides, or polymers that cannot be absorbed in their native form. Thus, these compounds must be hydrolyzed by intestinal enzymes or by colonic microflora in order to be absorbed. During the course of absorption, polyphenols are conjugated in the small intestine and later in the liver, through methylation, sulfation, and glucuronidation reactions. In the blood, polyphenols are conjugated derivatives bound to albumin. They penetrate into tissues where they are metabolized and then eliminated in urine and bile. For example, hydroxytyrosol shows strong antioxidant activity. In spite of this compound's great absorption capacity in the human body, its bioavailability is low. 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