Fish oils have been extensively researched with regard their ability to protect from cardiovascular disease. One mechanisms that has been proposed for their apparent protective effects is the ability to lower plasma triglyceride (very low density lipoprotein: VLDL) levels. Elevated levels of triglycerides are a risk factor for cardiovascular disease, and may be a reflection of increased de novo lipogenesis. Fish oils may lower triglyceride levels because they increase hepatic fatty acid oxidation and thus reduce the availability of fatty acids for triglyceride formation, and subsequent transport to peripheral tissues in the VLDL particles. This ability to lower plasma triglycerides could be considered a long-term benefit to fish oil consumption. However, fish oils have other shorter-term physiological effects that may explain their benefits to the cardiovascular system. For example, it has been shown that fish oils can decrease the variability in heart rate function, thus lowering the risk of arrhythmias, and this may subsequently decrease the risk of suffering a heart attack.
In a recent meta-analysis1, researchers reviewed the literature to investigate the effects of fish oil on heart rate variability in human subjects. The authors included 15 randomised controlled studies in the meta-analysis, and found that some of the parameters of heart rate variability were affected by fish oil supplementation. For example, vagal nerve function was significantly improved by fish oil supplements. When analysing the 15 papers, there was no significant improvement in the variability of heart rate function, but exclusion of 2 studies using less than 1000 mg of fish oil per day caused the results to become significant. Therefore heart rate variability improvements from fish oil supplements likely have a threshold dose of 1000 mg, below which improvements are not seen. As heart rate variability is an independent risk factor for cardiovascular disease and predicts cardiovascular mortality in patients with coronary artery disease and in healthy subjects, fish oils may therefore reduce cardiovascular mortality because they reduce the risk of arrhythmias.
RdB
