Omega-3 Benefits: Omega-3, cholesterol and cardiovascular risk
Omega-3 benefits for reducing cholesterol and cardiovascular risk factors
The cardiovascular benefits attributed to long-chain omega-3 polyunsaturated fatty acids (LC-PUFA) are the result of the following mechanisms: decrease in plasma triglyceride and LDL cholesterol levels, small increase in HDL cholesterol, decrease in blood pressure, platelet aggregation and incidence of arrhythmias.
Omega-3 effect on hypertriglyceridemia
The reduction in plasma lipids (especially triglycerides) produced by consuming Omega-3 LC-PUFA is one of the effects for which there is most evidence in both humans and animals.(1)Fish oils have been shown to reduce plasma cholesterol and triglyceride concentrations, inhibiting the biosynthesis of very-low-density lipoproteins (VLDL) and triglycerides in the liver, while slightly increasing that of high-density lipoproteins (HDL cholesterol) (2).
The effect on triglyceride, HDL and LDL cholesterol plasma concentrations is the opposite when oils rich in Omega-6 LC-PUFA are ingested, indicating that the Omega-3/Omega-6 fatty acid ratio acts as a liver sensor for regulating lipid metabolism.
Prevention of heart disease and Omega-3
The results of epidemiological and intervention studies indicate that the consumption of Omega-3 LC-PUFA may favourably affect cardiovascular health: The Seven Countries Study (20 years in length) concluded that men who consumed 30 g/d of fish reduced the risk of mortality due to heart disease by 50% compared to volunteers who did not consume fish;(3) the Western Electric Study, in which men who consumed more than 35 g/d of fish had a relative risk of mortality due to heart disease of 0.62 compared to those who hardly ever ate fish;(4) the study on the Prevention of Coronary Atherosclerosis by Intervention with Marine Omega-3 Fatty Acids (SCIMO) study showed a reduction in the development of atherosclerosis on administering 1.6 g/d of Omega-3 PUFA;(5) and the Diet and Reinfarction Trial (DART) established that doses of 2-3 g/week of Omega-3 LC-PUFA reduced the risk of suffering a secondary coronary episode and produced a drop of 30% in mortality due to cardiovascular disease (6); and in the GISSI-Prevenzione, consumption of a nutritional supplement of omega-3 DHA and EPA of 1 g/d reduced the risk of mortality due to heart disease by 17%, compared to the control group that did not consume the supplement.(7)
Hypertension and Omega-3
As well as improving lipid levels, Omega-3 LC-PUFA produces a small decrease in blood pressure. Omega-3 LC-PUFAs seem to exert beneficial effects on vascular smooth muscle by reducing intracellular calcium loss and the proliferation of smooth muscle cells (by inhibiting growth factors), while increasing nitric oxide production.(9)
Atherosclerosis and Omega-3
Atherosclerosis is a physiopathological process with multifactor origins, with two main components: dyslipidemia (high triglyceride and cholesterol levels) and inflammation. Consumption of Omega-3 LC-PUFA improves plasma lipid levels: low doses of fish oil can reduce the plasma concentration of triglycerides and slightly increase HDL cholesterol levels. The effect on plasma levels of triglycerides, HDL and LDL cholesterol is the opposite when oils rich in Omega-6 LC-PUFA are ingested(12), indicating that the Omega-3/Omega-6 fatty acid ratio acts as a hepatic sensor for regulating lipid metabolism.
The atheroprotective effect of Omega-3 LC-PUFAs also stems from its incorporation into cell phospholipids, where it partially replaces arachidonic acid as the initial substrate for the production of eicosanoids, except for prothrombotics and vasoconstrictors.(13)
Cardiac arrhythmias and Omega-3
As well as its effects on dyslipidemia and atherosclerosis, Omega-3 LC-PUFAs may also have an anti-arrhythmic effect (14). Its cardiac regulatory action is related to its capacity to inhibit L-type calcium channels in heart cells, thus prolonging the refractory period, lessening myocardium sensitivity to dangerous cardiac arrhythmias (9, 14, 15).
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