The invention relates to compositions of a natural origin, comprising hydroxytyrosol and polyphenols which are not hydroxytyrosol and do not occur naturally in the olive tree (O. europaea), characterized by allowing particularly high bioavailability of hydroxytyrosol and a particularly high antiatherosclerotic activity of hydroxytyrosol, once orally administered. Said compositions can consist of mixtures of plant extracts. The invention also relates to the use of said compositions for the treatment of cardiovascular diseases, particularly atherosclerosis.