*Geek Box: The HS-Omega-3 Index
The question over what to measure to obtain reliable measures of DHA + EPA levels has been examined in numerous studies, ultimately leading to an argument in favour of erythrocyte – red blood cell – measures. The Omega-3 Index was first proposed in 2004 and is calculated as the sum of DHA + EPA in RBCs, expressed as a percentage of the total fatty acids in the RBC measure.
Because DHA is the predominant omega-3 fatty acid in membrane phospholipids, DHA makes up the majority of the Index. This is not to suggest that EPA does not have important roles, however, it may mean that looking at EPA alone would not yield any meaningful findings.
The Omega-3 Index has been shown to be a robust predictor of cardiovascular disease. In addition, the Omega-3 Index appears to be stable and not easily altered by a given meal high in DHA + EPA, thus is a more reliable biomarker that is not easily influenced by recent dietary intake alone.
An attractive feature of the Omega-3 Index is that the analytical laboratory procedure has been standardised, which means the measure should be reproducible across populations: the standardised method is known as the HS-Omega-3 Index®. Of note, since the use of the standardised index populations in Korea and Japan – with generally higher fish consumption – have exhibited significantly higher indices than American populations. Lower Omega-3 Index is also quite consistently associated with worse outcomes compared to higher levels.
So, what is ‘low’ or ‘high’ for the Omega-3 Index? It appears that <4% is associated with worse health outcomes, particularly when compared to populations with levels of >8%. Populations in Scandinavia and Japan exhibit the highest Omega-3 Index levels.