Omega-3 Fatty Acids for the Primary and Secondary Prevention of Cardiovascular Disease

Background: Cardiovascular diseases (CVDs) are defined as conditions involving decreased blood flow to the heart that can lead to heart attacks, stroke or other disorders. CVDs are a common cause of death in low- and middle-income countries. In South Africa (SA) in particular, CVD is the leading cause of death after HIV/AIDS, responsible for 1 in 6 deaths. CVD risk factors include unhealthy diets, hypertension, obesity, high cholesterol levels and diabetes. Omega-3 fatty acids may have a protective role in the risk of developing heart disease.

Objectives: To evaluate the consequences of an increased intake of fish and plant-based omega-3 fatty acids on the risk of CVD mortality and events.

Methods: The inclusion criteria for this review were randomised controlled trials (RCTs) lasting at least 12 months, which investigated men and women aged ≥18 years. These participants had to be at any risk of CVD while receiving dietary supplements and an advised diet to promote the intake of omega-3. This diet included oily fish, fish oils and seeds rich in omega-3. Comparisons with the interventions included the participants' usual diet, no advice, no supplements, placebo or lower-dose omega-3. The review evaluated the effectiveness of these interventions on primary (e.g. CVD deaths and events), secondary (e.g. major adverse cerebrovascular or CVD events, body weight and other adiposity measures, and lipids) and tertiary (e.g. blood pressure and side-effects) outcomes.

Results: Evidence from this review indicates that increasing the intake of long-chain omega-3 fatty acids (LCn3) or alpha-linolenic acid (ALA) probably has little or no effect on all-cause CVD or coronary heart disease mortality. Evidence was of moderate certainty, except for all-cause mortality, where there was a high certainty.

Conclusions: According to moderate- to high-certainty evidence, short-chain fatty acids and LCn3 have little or no effect on mortality or cardiovascular health. However, omega-3 ALA slightly reduces the risk of CVD events and arrhythmias.