EDINBURGH, UNITED KINGDOM. It is well-established that consuming oily fish on a regular basis substantially reduces the risk of fatal coronary artery disease (sudden cardiac death) and also reduces the mortality among patients having suffered a heart attack. Similar beneficial effects have been observed with supplementation with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the main components of fish oil. It is generally believed that the beneficial effects are associated with their ability to reduce inflammation, prevent ventricular arrhythmias, and improve the stability of atherosclerotic plaque. Now researchers at the University of Edinburgh suggest that fish oils may also prevent the platelet activation involved in the formation of atherosclerotic lesions (atherosclerosis) and blood clots (thrombosis).
Their study involved 28 healthy, male volunteers between the ages of 21 and 28 years. The volunteers were assigned to two groups – the control group, and the intervention group who were asked to eat 500 mg of mackerel a week for 4 weeks; this would correspond to a daily intake of EPA+DHA of about 1 gram. Blood samples were taken at baseline, at 4 weeks, and at 8 weeks (for those in the intervention group only). Fatty acid content of plasma phospholipids was determined in all samples. The researchers also measured the level of platelet-monocyte aggregates, a highly sensitive marker of platelet activation. Platelet-monocyte aggregates appear to promote the formation of atherosclerotic lesions and their level is known to be increased in heart disease.
The researchers found, not too surprisingly, that plasma phospholipid content of EPA and DHA had increased markedly in the intervention group between baseline and week 4. Total omega-3 fatty acid content increased from 5.8% to 14.2%. Average EPA content rose from 1.0% to 5.2% with a corresponding increase in DHA content from 3.5% to 7.5%. No changes were observed in the control group. Four weeks after terminating the dietary intervention, EPA content had fallen to 1.8% and DHA concentration to 4.7%. Over the 4-week period, platelet- monocyte aggregation was reduced by 35% from 24.8% to 16.1% in the intervention group. There was a strong correlation between the extent of the reduction in platelet-monocyte aggregation and the level of EPA, DHA and total omega-3 fatty acids in plasma phospholipids.
The Scottish researchers conclude that regular consumption of oil-rich fish substantially reduces the level of circulating platelet-monocyte aggregates and may, through this mechanism, help prevent atherosclerosis and thrombosis.
Din, JN, et al. Dietary intervention with oil rich fish reduces platelet-monocyte aggregation in man. Atherosclerosis, Vol. 197, 2008, pp. 290-96