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Mediterranean Diet protects against cardiovascular diseases
Abstract
Mediterranean Diet protects against cardiovascular diseases
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Atherosclerosis, commonly known as hardening of the arteries, is the leading cause of morbidity and mortality in the world. According to Professor Michael Aviram, Head of the Lipid Research Laboratory at Rambam Medical Center and the Rappaport Institute,Technion Faculty of Medicine, Haifa.  Atherosclerosis is responsible for approximately 40% of deaths worldwide, annually. Prof. Aviram is one of the leading experts in the research on cholesterol  and lipoproteins, and the role played by dietary antioxidants in the fight against atherosclerosis. He has published over 350 original papers on the subject. Atherosclerosis begins with macrophage accumulation in the arterial wall (macrophages originate as monocyte white blood cells).  When the macrophage cell accumulates cholesterol and oxidized lipids from the uptake of LDL (the bad cholesterol) or oxidized LDL, the cell undergoes some changes and becomes a foam cell, so called because of its resemblance to foam when examined under a microscope.  These macrophage foam cells initiate the buildup of  atherosclerotic lesions in  the arterial walls.   If the deposits are in the arteries leading to the brain, the result is a stroke.  If they are in the arteries leading to the heart, the result is an heart attack. 
One of the most important contributions of the research emanating from Prof. Aviram’s laboratory to the field of atherosclerosis, is the finding that atherosclerosis is dependent  not only on the quantity of LDL , but also on its quality (such as cholesterol oxidation).  Oxidized LDL is a major risk factor for atherosclerosis.  In other words, even if the LDL level in the blood  is in the normal range, if it is oxidized, then it will be deposited in the arterial wall and thus it still represents a major risk factor for developing atherosclerosis.
For the last 20 years, Prof. Aviram has been investigating the role of antioxidants, mainly dietary antioxidants, in the fight against atherosclerosis.  Antioxidants prevent oxidation. Everyone is constantly exposed to oxidation, 24 hours a day, 365 days a year.  Oxidative stress (pro-oxidants)  surrounds us in the environment in which we live.  It comes from pollution, from chemicals, from smoking, from viruses and from bacteria.  Endogenous antioxidants, such as vitamins E and C are our body’s protectors against harmful  oxidation.  However, we do not produce enough of them to fight the excess oxidative stress.  Therefore, we need to increase the intake of antioxidants, preferably from fruits and vegetables.  The antioxidants in fruits and vegetables are found mostly in their peels and seeds, but mainly in the peels.  Not only do these fruits and vegetables protect humans from oxidative stress, they also prevent the oxidation of the fruits or vegetables themselves. 
Prof.  Aviram has studied 65 different fruits and vegetables for their antioxidant potency.  He found that almost all of them contain antioxidants.    However, the difference in the potency and specificity (meaning the type of antioxidant) is huge.  In human clinical trials, both vitamin E and carotenoids (beta-carotene) did not show a significant effect on cardiovascular diseases.  Prof. Aviram’s  laboratory found that polyphenols  (flavonoids) are the most potent type of  dietary antioxidant.   Out of the fruits and vegetables studied by Prof. Aviram, three of them were found to be the most potent.  He was the first researcher to show the protection of pomegranate juice, red wine and licorice root extract against cardiovascular diseases in humans.   At the present time we do not consume enough fruits and vegetables to get enough of the antioxidants.  Prof. Aviram was looking for an additional antioxidant in the body which would be different in its action than dietary antioxidants.  In other words, he was  looking for some agent, some enzyme, some chemical in the body, that can possibly break down oxidized lipids in oxidized LDL, and by so doing, reduce the level of oxidized LDL; not because less oxidized LDL is formed, but because the already existing oxidized LDL is broken down.  His laboratory did find such an agent.  This agent is called Paraoxonase.  Paraoxonase is an enzyme which is present in our blood and associated with HDL.  HDL is the good cholesterol (maybe it’s good cholesterol because it contains Paraoxonase).Prof. Aviram states that “what we really want at the end of the day is to reduce oxidative stress in our bodies in order to have less oxidized LDL.  We can do it by inhibiting the production of oxidized LDL by dietary antioxidants on one hand, while at the same time, increasing the breakdown of the already existing oxidized LDL by increasing paraoxonase levels”.  Prof. Aviram found that some dietary antioxidants, the major one being pomegranate juice increases paraoxonase activity.  Pomegranate juice contains the highest antioxidant capacity compared to other juices, including red wine , olive oil , and green tea.  In his studies pomegranate juice was found to slow down cholesterol oxidation by almost half, as well as to reduce the retention of LDL to the arterial wall.  So, here we see a nice link between dietary antioxidants and paraoxonase, both resulting in less oxidative stress, and less oxidized LDL accumulation which reduces the risk for cardiovascular events, such as a heart attack or stroke.