Raised levels of certain plasma lipoproteins are associated with an increased risk of cardiovascular disease. In particular, increases in the amount of the small dense low density lipoprotein (LDL), lipoprotein(a) and the very low density lipoprotein (VLDL) particles are associated with an increased risk of cardiovascular disease. In addition, lowered levels of the high density lipoprotein (HDL) particle also increase the risk of developing cardiovascular disease. Lipoprotein chemistry is very complex and the exact role each lipoprotein particle plays in humans is not fully understood. However, it is important to understand that changes to lipoproteins are associated with cardiovascular disease, but the cause and effect cannot be attributed. In fact, evidence suggests that is not the lipoprotein changes themselves that cause cardiovascular disease, but an underlying metabolic syndrome that leads to both cardiovascular disease and changes to blood levels of lipoproteins.
Forcing down blood lipoprotein levels does not therefore necessarily reduce the risk of cardiovascular disease, unless it is through addressing the underlying metabolic problems that are the likely cause of both the aberrant lipoprotein levels and the cardiovascular disease. Therefore certain drugs that inhibit cholesterol synthesis in the liver may not be beneficial in this regard. Fish oils have been extensively researched for their ability to lower the plasma levels of very low density lipoprotein (VLDL) and in this role they appear to be highly effective. For example, in one study1 researchers tested the effects of 100 grams of fatty fish twice a week for 3 months. During this time the mean plasma very low density lipoprotein (VLDL) levels (also sometimes called plasma triglycerides) fell significantly by 6.7 %. However, there were no changes to other lipoproteins supporting the contention that fish is able to favourably affect plasma triglycerides but not other lipoproteins.
In this study the authors calculated that the intake of eicosapentaenoic acid (EPA, C20:5 (n-3)), that is thought to be responsible in part for the beneficial effects of fish, was a modest 0.3 to 0.6 grams per day. This would be roughly equivalent to one small fish oil capsule. Epidemiological studies suggest that fish consumption is beneficial at preventing cardiovascular disease. The reason for the protective effects of fish is likely that they provide the body with the fatty acids that are essential to the production eicosanoids that favourably reduce inflammation. Their triglyceride lowering effects may also stem from the ability of polyunsaturated fatty acids to stimulate fatty acid oxidation in the liver. As fatty acid accumulation in the liver is partly responsible for the development of the metabolic syndrome that is a likely cause of cardiovascular disease, fish oils may reverse some of the detrimental effects of these fatty acids. Fish oils therefore likely have multiple cardioprotective mechanisms of action.
Dr Robert Barrington’s Nutritional Recommendation: Fatty fish are beneficial to the health because they supply metabolites of the essential fatty acid alpha linolenic acid (ALA, C18:3 (n-3)) that can feed into the essential fatty acid pathway and produce beneficial metabolic effects. The idea that cardiovascular disease may in part be caused by an essential fatty acid deficiency has not gone unnoticed by nutritionists. Consuming fatty fish or their oils is one of the most cardioprotective nutritional strategies that has been identified to date.
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