Understanding how the omega-3 index influences heart health


Cardiovascular disease is the leading cause of death in many developed countries, and its incidence is increasing at a rapid rate in developing countries.  Diet and lifestyle issues are closely associated with a myriad of cardiovascular disease risk factors that include abnormal cholesterol levels, high lipid levels, hypertension, insulin resistance, diabetes and obesity. It is widely recognised that diet-based approaches may be of benefit.

Compelling evidence exists for the cardio-protective benefits resulting from the consumption of fatty acids derived from fish.  The omega-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) are a unique class of fatty acids that have well established benefits on cardiovascular risk factors.   For example, the omega-3 index, defined as the percentage of EPA plus DHA in red blood cell fatty acids, is becoming increasingly recognised as an indicator of cardiovascular health.1 Using data from several secondary prevention studies, it has been possible to estimate the omega3 index associated with low and high risk for death from cardiovascular disease and an erythrocyte omega3 index level of ≥8% has been proposed as a reasonable target value for reducing risk. Indeed, an omega-3 index less than 4% is generally associated with a tenfold risk for sudden cardiac death in comparison to an omega-3 index greater than 8%.  In the UK, as well as in other Western nations, these important fatty acids are consumed in quantities that fall below government guidelines, raising issues for long-term cardiovascular health.  Increasing intake of these long-chain fatty acids can therefore have a major impact on heart health, not only in prevention, but also in secondary care. Evidence for the cardio protective effects of these long-chain fats, and in particular EPA, have shown huge potential in secondary prevention of coronary artery disease.  As well as its potent anti-inflammatory effects, EPA exhibits anti-arrhythmic effects, inhibits platelet aggregation thereby improving circulation, lowers cholesterol, has triglyceride-lowering effects, and has a favourable effect on plaque formation – one of the biggest influences in developing a heart attack.   Indeed, it has been proposed that these effects may function synergistically to reduce the risk of coronary artery disease.   As such, the potential of EPA in modulating cardiovascular disease had been the focus of many large intervention studies such as The Japan Lipid Intervention Study, the first prospective randomised clinical trial to demonstrate the preventative coronary events by pure EPA.

However, recent evidence suggests that increasing the omega-3 index may be of benefit to those individuals who not only have some form of cardiovascular risk factor, but also those suffering from heart failure.2 Unlike cardiovascular disease, heart failure is the inability of the heart to pump blood efficiently enough to provide adequate flow to the body and organs and usually occurs as the end point of several possible disease processes that lead to weakness of the heart muscle.  Chronic congestive heart failure is extremely common and is estimated to affect 400,000 people in the UK, with approximately 8000 at an advanced stage.  Few previous studies have evaluated associations between long-chain omega-3 fatty acids and incidence of congestive heart failure and those that have are typically based on diet questionnaires and yield conflicting results.  However, by measuring fatty acids in blood samples, which provides more detailed information on actual fatty acid levels as a biomarker of dietary intake, researchers in the USA have made significant findings regarding the individual fatty acids EPA and DHA.  Circulating individual and total omega-3 fatty acid concentrations were found to be directly associated with lower incidence of congestive heart failure in older adults.  What was particularly striking about their results was that, whilst plasma phospholipid EPA concentrations were inversely associated with the incidence of congestive heart failure (with risk approximately 50% lower for those with the highest versus the lowest levels of EPA), no such association was reported for DHA alone.  These findings appear to add increasing value to the use of ethyl-EPA as a standalone treatment for supporting heart health.  For example, ethyl-EPA is already being hailed as the ‘gold standard’ regarding its preventive mechanisms and The American Heart Association has issued recommendations stating that individuals with hypercholesterolaemia (high cholesterol) or hypertriglyceridaemia (high lipids) may benefit from taking 1.8 g of pure EPA per day.  Given that such conditions  take years, perhaps decades, to reach such negative end points, it seems prudent to advise healthy individuals to think of their long term heart health by increasing their EPA intake whilst young.

  1. von Schacky C. The Omega-3 Index as a risk factor for cardiovascular diseases. Prostaglandins Other Lipid Mediat. 2011 Jun 24. [Epub ahead of print]
  2. Mozaffarian D, Lemaitre RN, King IB, Song X, Spiegelman D, Sacks FM, Rimm EB, Siscovick DS. Circulating Long-Chain {omega}-3 Fatty Acids and Incidence of Congestive Heart Failure in Older Adults: The Cardiovascular Health Study: A Cohort Study. Ann Intern Med. 2011 155:160-70.

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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.