Very low density lipoproteins (VLDL) represent the lipoprotein fraction measured as plasma triglycerides. Following absorption to the plasma within chylomicrons, triglycerides are passed to the liver where they are arranged into VLDL particles. The composition of the VLDL particles therefore reflect the composition of the dietary fatty acids ingested. Increasing dietary intake of unsaturated fatty acids can have a pronounced effect on the percentage of unsaturated fatty acids found in plasma triglycerides, and also on the composition of the adipose tissue, the destination of the VLDL particles. While the VLDL particles transport triglycerides to the adipose tissue, the low density lipoproteins (LDL) transport mainly cholesterol from the liver to the peripheral tissue. However, the LDL particles also contain a relatively small concentration of triglycerides and evidence suggests that the fatty acid composition of LDL can be altered by dietary changes to fatty acid intake.
Altering the composition of LDL particles through dietary manipulation might be beneficial because some sub-types of LDL are involved in the formation of atherosclerosis. The fatty acid composition may alter not only the susceptibility of LDL particles to oxidation, but also the interaction of LDL with the endothelial tissue of arteries. Of particular benefit may be the monounsaturated oleic acid (OA, C18:1 (n-9)) in olives, which some research has shown may protect from cardiovascular disease. To investigate this, researchers1 fed 25mL per day of olive oil to 200 healthy subjects, and then assessed the effects of the oil on LDL composition. Following the three week intervention, the OA content of LDL particles increased, while the content of linoleic acid (LA, C18:2 (n-6)) and arachidonic acid (AA, C20:4 (n-6)) decreased. In addition, there was an inverse relationship between the OA/LA ratio and biomarkers for oxidative stress.
Therefore the monounsaturated to polyunsaturated fatty acid ration of LDL particles can be increased through olive oil consumption. This appears to change the susceptibility of LDL to oxidation, which was measured as a 4.2µg/L decreased in isoprostane for each unit increase in the OA to LA ratio. Oleic acid consumption therefore causes beneficial lipoprotein changes that could be interpreted as protective of cardiovascular disease. Controversy exists as to whether the benefits of olive oil derive from the monounsaturated fatty acids or the phytonutrient antioxidants contained within the oil. Evidence supports the contention that the phytonutrients are the most beneficial component, but some evidence does suggest that the fatty acids themselves may be beneficial. As this study shows, this may result from displacement of LA and AA from cell membranes, thus reducing their n-6 content and decreasing the synthesis of pro-inflammatory eicosanoid formation.
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