Omega-3 fatty acids in heart disease—why accurately measured levels matter

Current guidelines barely support marine omega‑3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in cardiology, mainly because results of large trials were equivocal. Most large trials have tested EPA alone or EPA + DHA combined as a drug, thereby disregarding the relevance of their blood levels. These levels are frequently assessed with the Omega‑3 Index (percentage of EPA + DHA in erythrocytes), which is determined using a specific standardised analytical procedure. EPA and DHA are present in every human being at unpredictable levels (even in the absence of intake), and their bioavailability is complex. Both facts need to be incorporated into trial design and should direct clinical use of EPA and DHA. An Omega‑3 Index in the target range of 8–11% is associated with lower total mortality, fewer major adverse cardiac and other cardiovascular events. Moreover, functions of organs such as the brain benefit from an Omega‑3 Index in the target range, while untoward effects, such as bleeding or atrial fibrillation, are minimised. In pertinent intervention trials, several organ functions were improved, with improvements correlating with the Omega‑3 Index. Thus, the Omega‑3 Index is relevant in trial design and clinical medicine, which calls for a widely available standardised analytical procedure and a discussion on possible reimbursement of this test.