Triglyceride management in cardiovascular health: EPA triumphs over DHA

The heart health benefits of omega-3s in fish oils are well established, and many of us may be supplementing daily to help control our triglyceride and/or cholesterol levels. Not all fish oils are equal, however, in terms of active ingredients and their benefits – some, it seems, may actually be doing more harm than good according to the results of a new study published in the September issue of the American Journal of Cardiology.

Cholesterol and triglycerides are types of fat (or lipid) that circulate within the bloodstream and generally get quite bad press. Whilst it is important to keep tabs on both types of fat, they actually have important structural and functional roles within the body, and we can’t do without them. Cholesterol is required for building and maintaining cell membranes, and is the precursor to several essential hormones. Triglycerides, which are actually chains of fatty acids, provide us with a direct source of energy. Having too many circulating triglycerides is often a sign of metabolic syndrome, which can lead to type II diabetes as well as raising the risk of heart disease. The chances are, if you have high triglycerides you may also have high cholesterol levels.

Cholesterol travels the body in the form of lipoproteins, of which there are several types. The most significant and well known ones are: high density lipoprotein (HDL) cholesterol – often called “good” cholesterol, and low density lipoprotein (LDL) cholesterol – often called “bad” cholesterol. When LDL cholesterol levels are too high, the LDL lipoprotein tends to stick the lining of the blood vessels that may lead to atherosclerosis, the development of sticky plaques that can build up and obstruct the normal blood flow. An elevated LDL cholesterol level is therefore a major risk factor for heart disease and stroke. In contrast, HDL lipoprotein “scours” the walls of blood vessels removing excess cholesterol and transporting it back to the liver for processing. Having higher HDL levels than LDL is essential for a healthy cardiovascular system.

Omega-3 fatty acids, especially EPA and DHA found in fish and fish oil, are highly effective in lowering elevated blood triglyceride levels and have become an increasing treatment option, as an alternative to pharmaceutical medication. Whilst fish oils have been shown to lower triglyceride levels, a ‘side effect’ has been observed with generic EPA and DHA combined oils – they actually increase LDL levels, thus cancelling out some of the benefits in terms of reducing the risk of developing heart disease. This isn’t bad news for all fish oils, however. When researchers looked at the individual actions of EPA and DHA by way of head to-head comparison studies of EPA and DHA in patients with dyslipidemia, both EPA and DHA lowered triglyceride levels, but only DHA raised LDL levels. Such findings have led to an increased interest in treatments using ethyl-EPA only oils and the aptly named MARINE study was the latest of several to report its findings (Bays et al, 2011)

This double-blind study randomized 229 dyslipidemia, patients (with or without background statin therapy) to 12 weeks of supplementation with ethyl-EPA 4 g/day, ethyl-EPA 2 g/day, or placebo. Compared to the placebo, after three months of treatment, ethyl-EPA 4 g/day reduced placebo-corrected median triglceride levels by approx 33.1% and 2 g/day by approx 20%. Importantly, neither ethyl-EPA 4 g/day nor 2 g/day significantly increased the LDL cholesterol levels, but both significantly reduced very low density lipoprotein cholesterol (VLDL) and total cholesterol, with no significant effect on HDL cholesterol.

Such studies are invaluable for clarifying the individual and unique properties of EPA and DHA. Given that fish species – and to some extent fish oils – hold very different ratios of EPA and DHA, it is not surprising that epidemiological studies, as well as intervention studies, have diverse and often times conflicting outcomes. These differing outcomes are seen not only with cardiovascular and heart health, but a number of other areas such as depression and neurodevelopmental disorders, where EPA over DHA is being recognised as the predominant protective/active fatty acid. Certainly increasing numbers of studies and meta-analysis of large numbers of studies are recognising the importance of the EPA to DHA ratio within treatment oil (Bloch & Qawasmi 2011; Sublette et al, 2011).

Bays HE, Ballantyne CM, Kastelein JJ, Isaacsohn JL, Braeckman RA, Soni PN. Eicosapentaenoic acid ethyl ester (AMR101) therapy in patients with very high triglyceride levels (from the Multi-center, plAcebo-controlled, Randomized, double-blINd, 12-week study with an open-label Extension [MARINE] trial). Am J Cardiol 2011;108(5):682-90.

Bloch MH, Qawasmi A. Omega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis. J Am Acad Child Adolesc Psychiatry 2011;50(10):991-1000.

Sublette ME, Ellis SP, Geant AL, Mann JJ. Meta-analysis of the effects of eicosapentaenoic acid (EPA) in clinical trials in depression. J Clin Psychiatry 2011.

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Dr Nina Bailey

About Dr Nina Bailey

Nina is a leading expert in marine fatty acids and their role in health and disease. Nina holds a master’s degree in Clinical Nutrition and received her doctorate from Cambridge University. Nina’s main area of interest is the role of essential fatty acids in inflammatory disorders. She is a published scientist and regularly features in national health publications and has featured as a nutrition expert on several leading and regional radio stations including SKY.FM, various BBC stations and London’s Biggest Conversation. Nina regularly holds training workshops and webinars both with the public and health practitioners.