Fish Oil and the Heart
CHIETI, ITALY. Several large clinical trials have confirmed the ability of fish oils to prevent sudden cardiac death in both presumably healthy subjects as well as in patients having suffered a heart attack (myocardial infarction). Considering that sudden cardiac death, largely caused by ventricular fibrillation, accounts for somewhere between 250,000 and 300,000 deaths every year in the US alone, it is clearly highly significant that a diet rich in oily fish or fish oil supplements may reduce the incidence of sudden cardiac death by up to 45%.
Researchers at the universities of Chieti and Pisa published a review of the current “state-of-the- art” in regard to fish oil and heart health. Below are some highlights that outline some of the benefits of fish oil and the heart.
Benefits of Oily Fish and Fish Oil Supplements
- Those who used fish oil supplements showed its beneficial effect within a few weeks.
- It is unlikely that the biological effects of fish oils would vary depending on source (oily fish or fish oil supplement).
- Animal experiments have shown that fish oils act on individual myocytes (heart cells) to inhibit the excitatory Na+ current, stabilize the inactivated state of the Na channel, and prolong the effective refractory period of the cardiac cycle. The L-type Ca++ current is also inhibited by fish oils and the outward flow of K+ is reduced. All effects which would reduce the tendency to arrhythmia either by decreasing automaticity or by interfering with re-entry circuits.
- Two small trials have shown a reduction in PVCs (premature ventricular complexes) with fish oil supplementation. In one of these trials 34 participants with frequent PVCs, but no life-threatening arrhythmias were given 2.4 grams/day of fish oils while the control group was given sunflower seed oil which is rich in linoleic acid (an omega-6 fatty acid). PVCs decreased by 48% in the fish oil group as compared to 25% in the sunflower seed group.
- Fish oils and fish oil supplements have been shown to decrease heart rate variability and there is some suggestion that they may also reduce sympathetic and increase parasympathetic (vagal) activity in the autonomic nervous system.
- Prostaglandins and thromboxane A2, produced from arachidonic acid, are mostly proarrhythmic so a high intake of omega-6 fatty acids may be detrimental.
Although most research, so far, has focused on the effect of fish oil on life-threatening ventricular arrhythmias, it is likely than many of the findings may also be applicable to atrial fibrillation. Researchers continue to uncover new discoveries relating to the benefits of fish oil and heart health.
De Caterina, Raffaele, et al. Antiarrhythmic effects of omega-3 fatty acids: from epidemiology to bedside. American Heart Journal, Vol. 146, September 2003, pp. 420-30