Epidemiological data support a lower incidence of cardiovascular diseases in the Mediterranean area compared with the rest of Europe . These findings were attributed to the traditional Mediterranean diet , with its characteristically high consumption of olive oil and olives. The olive products constitute a rich source of polyphenols such as oleuropein and its derivatives, including hydroxytyrosol, which scavenge free radicals and inhibit the chemical oxidation of LDL . Diets rich in olive oil reduce tissue oxidative stress and enhance the glutathione antioxidant defense system in atherosclerotic rabbits, whereas diets rich in polyphenols are currently recommended for the prevention of atherosclerosis.

The main constituent of the leaves and unprocessed olive drupes of Olea europaea is oleuropein, and the majority of the polyphenols found in olive oil or table olives are products of its hydrolysis. Oleuropein has high antioxidant activity in vitro, comparable to a hydrosoluble analog of tocopherol . Oleuropein scavenges superoxide anions and hydroxyl radicals, and inhibits the respiratory burst of neutrophils and hypochlorous acid–derived radicals. The oxygen-derived free radicals contribute to the pathogenesis of atherosclerosis by oxidizing LDL and generating several species that react with oxygen in the vascular wall. Diets rich in saturated fatty acids lead to increased oxidative stress in different tissues of rabbits. In contrast, dietary supplements containing olive oil reduce lipid peroxidation and favor tissue antioxidant defensive mechanisms mediated by the glutathione system . Furthermore, olive oil reduces hyperlipidemia and decreases the atherogenic index.