Consuming more fruits and vegetables provides the body with a broad spectrum of antioxidants such as carotenoids, anthocyanin’s, Vitamin C and E which have been shown to prevent oxidative damage of LDL carrying proteins. Free radical oxidation of LDL and VLDL lipid transporting proteins is the first step in atherogenesis. The reason LDL and VLDL are subject to oxidation is because of their molecular makeup. LDL (low density lipoprotein) is composed of an estimated 3000 fatty acids and over half of those 3000 fatty acids are polyunsaturated such as Docosahexaenoic acid, Arachidonic acid. On the surface of LDL lipid transporting proteins is a plasma glycoprotein known as Apolipoprotein B (apo b) which contains a total of 356 positively charged amino groups which are recognized by the LDL receptor for incorporation into the cell. Any changes to these positively charged amino groups as is the case with exposure to reactive aldehydic groups, which are organic compounds formed from reactive oxygen species, attenuates the binding of LDL to the LDL receptor. This negative interaction with aldehyde groups increases the binding and uptake of oxidized LDL by macrophages. LDL polyunsaturated fats are easily subject to oxidation and within this matrix of cholesterol esters, free cholesterol, phospholipids and triglycerides are antioxidants such as alpha tocopherol and beta carotene which prevent lipid peroxidation. There are three consecutive phases to LDL oxidation, the first being the lag phase which lasts as long as Vitamin E and carotenoids prevent oxidation of lipids within LDL. When they’re exhausted the second phase known as propagation starts. This second phase occurs when the antioxidants are exhausted and the onset of lipid peroxidation begins. As the aldehydic lipid peroxidation products increase, the last phase of LDL oxidation sets in known as decomposition. The structure of apo-b changes and oxidized LDL is rapidly degraded by macrophages leading to foam cell formation a critical step in atherogenesis.
Springer Journals: Free Radicals and Aging: Inhibition of LDL oxidation by antioxidants, Hermann Esterbauer, Georg Waeg, Herbert Puhl, M. Dieber-Rotheneder and Franz Tatzber, 1992
By Tommy Brooks