Omega-3 has been a popular supplement for some time now, but what is it and what does it do? Does it really give any health benefits? As research into this topic continues, it’s becoming clear that omega-3 already has great health benefits and, with careful use, could have even more.

Omega-3 is a fatty acid, and there are three main types involved in human physiology.  One, α-linolenic acid (ALA), is found in plant oils.  Another two are commonly found in marine oils such as fish oil, krill oil, algal oil etc, and are called eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).  We will focus on the latter two types, EPA and DHA, as these seem to be much more important in improving functioning.  It can be hard for humans to synthesise these longer chains from the shorter chain ALA, with less than 5% conversion efficiency [2].  Therefore, it is important that our diets contain sufficient levels of EPA and DHA.  DHA is a major structural component of the brains of mammals, and is the most abundant fatty acid in our brains [5].  Unsurprisingly, there is already evidence that suggests omega-3 has beneficial effects for those suffering from depression [4,7,8,9].  There is also mounting evidence that omega-3 could play a significant role in protecting the heart and circulatory systems [10], particularly in those who have a depressive disorder [1].

To test whether omega-3 is having a protective effect to the heart or circulation, first of all one must measure the levels of omega-3 in the body.  This is done using the Omega-3 Index.  This measures the percentage of EPA and DHA in red blood cells [3].  It is much more effective at assessing omega-3 levels in the body than measuring omega-3 intake [11].  The mean level of omega-3 between populations varies widely.  However, within a population the levels follow a normal distribution [12].  So in each population, some individuals will have high levels, and some low, with the majority in the middle.  The Omega-3 Index rating reflects the levels of EPA and DHA found in body tissues, for example in the heart [12].  A low Omega-3 Index rating is a strong predictor of future adverse cardiovascular events [12].

In two case–control studies on sudden cardiac death in the US, levels of omega-3 fatty acids in red cells or whole blood were inversely related to risk for sudden cardiac death, and a 10-fold difference in risk was reported [10]. Thus, a high omega-3 Index rating, for example 8–11%, is associated with a low risk for sudden cardiac death, and the risk appears to increase with decreasing ratings on the Omega-3 Index [10].

Accordingly, in Japan the mean Omega-3 Index rating was found to be 9.58%, and the incidence of sudden cardiac death is 7.8 deaths per 100,000 people each year.  In Western countries, the mean Omega-3 Index rating is approximately 5% and the incidence of sudden cardiac death is 150 deaths per 100,000 people per year.  Sudden cardiac death is responsible for 15% of deaths in Western Countries [10].

So, there is a correlation between Omega-3 Index values and hearth health.  But can we influence these values to increase our Omega-3 Index rating, and so improve our heart health?  The answer seems to be yes (Kohler a 2010).  The level of Omega-3 Index rating is influenced by the consumption of EPA and DHA through our diets.  According to von Schacky [10], every 4g of EPA and DHA ingested per month increased the Omega-3 Index rating by 0.24%.


One can see the cumulative effects of supplementing your omega-3 consumption could take you from a low Omega-3 Index level to the higher, protective levels, indicated by the studies mentioned above.  There are some  products handily comes with a test you can perform at home.  Before you start taking the oil containing omega-3, you can measure your own omega-3 values.  You then measure them again after 120 days of taking the oil, to see how your omega-3 levels have risen.  In this way, you can actually follow your increase in heart health and health overall!


1. Baghai TC et al.  Major depressive disorder is associated with cardiovascular risk factors and low Omega-3 Index. J Clin Psychiatry. (2011) Sep;72(9):1242-7.

2. Gerster H. Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)?”. Int. J. Vitam. Nutr. Res. (1998) 68 (3): 159–173.

3. Harris WS, Von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease?  Prev Med. (2004) Jul;39(1):212-20.

4. Hegarty B, Parker G Fish oil as a management component for mood disorders – an evolving signal.  Current Opinion in Psychiatry (2013). January, 26 (1): 33–40.

5. Huppi PS.  Commentary – Nutrition for the Brain.  Paediatric Research. (2008) Vol. 63, No. 3.

6. Köhler A et al.  Effects of a convenience drink fortified with n-3 fatty acids on the n-3 index.  Br J Nutr. (2010) Sep;104(5):729-36.

7. Montgomery P, Richardson AJ (2008-04-16). Montgomery, Paul, ed. Omega-3 fatty acids for bipolar disorder”. Cochrane database of systematic reviews (Online)(2): CD005169

8. Pottala JV et al.  Red blood cell fatty acids are associated with depression in a case-control study of adolescents.  Prostaglandins Leukot Essent Fatty Acids. 2012 Apr;86(4-5):161-5.

9. Ruxton CHS et al.  The impact of long-chain n-3 polyunsaturated fatty acids on human health. Nutrition Research Reviews (2005). 18 (1): 113–129.

10. Von Schacky C.  Omega-3 Index and Sudden Cardiac Death.  Nutrients. (2010) Mar; 2(3): 375–388.

11. Von Schacky C.  Omega-3 fatty acids vs. cardiac disease–the contribution of the omega-3 index.  Cell Mol Biol (Noisy-le-grand). (2010) Feb 25;56(1):93-101.

12. Von Schacky C.  The Omega-3 Index as a risk factor for cardiovascular diseases. Prostaglandins Other Lipid Mediat. (2011) Nov;96(1-4):94-8

13. Wall R, et al. “Fatty acids from fish: the anti-inflammatory potential of long-chain omega-3 fatty acids”. Nutr Rev 68  (2010) (5): 280–9.