ABSTRACT
Introduction Adherence to a Mediterranean diet is likely to lower the risk for cardiovascular disease (Trichopoulou et al., 2003; Trichopoulou et al., 2005) and certain cancers (Trichopoulou et al., 2000; Trichopoulou et al., 2003). Even though cardiovascular risk and coronary heart disease (CHD) have always been associated with classic risk factors such as high serum cholesterol and blood pressure, evidence shows that the prevalence of such factors does not differ significantly between the populations of the Mediterranean area-where the incidence of CHD and certain cancers, e.g. breast and colon cancers, is lowest-and those of other North-European and Western countries (Parfitt et al., 1994). Moreover, there are several observations that do not completely link CHD incidence, fat intake, and absorption (Mancini and Rubba, 2000). Taken together, these data suggest that other, as yet unexplored, risk factors may be favorably affected by a healthful diet (Mancini and Rubba, 2000). Indeed, several studies demonstrate that oxidative processes in the endothelium play a role-the extent of which is yet to be fully understood-in the onset of atherosclerosis (Steinberg et al., 1989; Stocker and Keaney, 2004). ese processes exacerbate inflammation and greatly increase the risk for atherosclerosis and CHD (Ross, 1999). Such experimental data led to the formulation of an oxidant/atherosclerosis hypothesis, which has been receiving increasing experimental support. e precise nature of the phenomena that trigger the development of atheroma and the extent of their contribution to CHD are yet to be fully elucidated. Based on this evidence, experimental and epidemiological studies are being carried out on the possible role of antioxidants in the relative protection from CHD observed in the Mediterranean area. In the past, coupled with the low consumption of meat, major emphasis was put on the low saturated fat content (and the concomitant high proportion of monounsaturated fat) of the Mediterranean diet. More recently, research has underlined the importance of plant foods (including carbohydrates and non-digestible fiber) and of the regular use of olive oil. e latter has been traditionally endorsed with healthful
and even medicinal properties. As far as the cardiovascular system is concerned, the protective properties of olive oil have been, until recently, exclusively attributed to its high monounsaturated fatty acid (MFA) content, mostly in the form of oleic acid (18:1n-9). Indeed, monounsaturate supplementation leads to enhanced resistance of LDL to oxidation (Bonanome et al., 1992), hence lowering one of the risk factors for CHD (Witztum and Steinberg, 2001). Appropriately, the US Food and Drug Administration recently allowed a qualified health claim for monounsaturates from olive oil and reduced risk of CHD (FDA, P04-100, 2004). However, several observations argue against the hypothesis of oleic acid as the exclusive responsible factor for the lower rates of CHD of the Mediterranean area. For example, the effects of MFA on circulating lipids and lipoprotein have not been fully clarified. While the major effects of high monounsaturated fatty acid intakes on serum cholesterol are generally thought to be indirect and have been attributed to the associated replacement of saturated fatty acids (Belkner et al., 1993; Hegsted et al., 1993; Gardner and Kraemer, 1995), some studies (reviewed by (Mensink et al., 2003), attributed a direct, although modest, cholesterol-lowering effect to MFA alone, when they equicalorically replace carbohydrates. Also, MFA increases the levels of the protective high-density lipoprotein (HDL) more than polyunsaturates (PUFAs) when these two classes of fatty acids replace carbohydrates in the diet (Mensink et al., 2003); however, there are reports of a neutral effect of MFA on plasma lipids or even a total-and LDL-cholesterol lowering activity. In turn, while oleic acid might exert some beneficial effects on the serum lipid profile, its actions are of moderate magnitude at best. Most important, oleic acid is one of the predominant fatty acids in largely-consumed animal foods such as poultry and pork. us, contrary to the common belief, the percentage of oleic acid in the Mediterranean diet as a whole is only slightly higher than that of other kinds of Western diets, e.g. the North American one (Dougherty et al., 1987; Katan, 1995). It is therefore unlikely that oleic acid is exclusively accountable for the healthful properties of olive oil. Finally, it is also noteworthy that several seed oils obtained through genetic selection, such as sunflower, soybean, and rapeseed oils are nowadays rich in monounsaturated, albeit devoid of phenolics (Owen et al., 2000), and are commercially available. Consumption of such oils, namely rapeseed, is widespread in several areas of the world (Gunstone, 2004): if oleic acid were endowed with strong cardioprotective effects, similar low incidence of CHD and high longevity would be observed outside the Mediterranean basin. is chapter reviews the evidence that indicates how the phenolic components of extra virgin olive oil may play a role in the protection from CHD and cancer observed in the Mediterranean area.
