PITTSBURGH, PENNSYLVANIA. Researchers at the National Institutes of Health and 10 major US hospitals and universities provide an excellent summary of the current knowledge regarding the benefits of omega-3 fatty acids in the prevention of cardiac arrhythmias. There is overwhelming evidence that an adequate intake of the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is highly protective against sudden cardiac death (SCD), which is caused by ventricular arrhythmias in 80-90% of cases. A high blood level of EPA and DHA was associated with an 81-90% reduction in SCD in a group of healthy people without known coronary heart disease. As little as 1 gram a day of EPA and DHA (found in oily fish and fish oils) has also been found to be highly protective against SCD in patients having suffered a pervious heart attack. The American Heart Association now recommends that all adults consume fish, preferably fatty, at least twice a week, and that patients with coronary heart disease consume 1 gram a day of EPA and DHA combined.
The effect of oily fish consumption or fish oil supplementation on atrial fibrillation is less clear. One study involving 4815 men and women 65 years or older (mean age of 73 years) found that consumption of baked or broiled fish was associated with a significantly reduced risk (31%) of developing AF over a 12-year follow-up period. In contrast, a study involving 48,000 much younger people (mean age of 56 years) found an increased risk (34%) of AF with increased fish consumption over a 5.7-year follow-up period. A randomized trial of fish oil supplementation (850 mg EPA+DHA) prior to bypass surgery found that 15% of patients randomized to fish oil developed post- procedure AF as compared to 33.3% in the control group.
The researchers suggest that the reason for the discrepancy between the results of the trial involving younger people and the one involving older people could well be that fish oils tend to increase parasympathetic (vagal) tone and this could be detrimental in younger people, while it may be beneficial in older people where sympathetic (adrenergic) tone tends to dominate. Older people would also be more likely to have systemic inflammation and atrial fibrosis which may be reduced by a high intake of long-chain omega-3 fatty acids.
Dietary supplementation with long-chain omega-3 fatty acids (fish oils) is known to change the composition of lipid membranes toward greater fluidity. There is also evidence that fish oil supplementation inhibits a number of sodium, potassium and calcium channels in a beneficial way and reduces the production of pro-inflammatory thromboxanes – all actions that could reduce the incidence of cardiac arrhythmias.
London, B, et al. Omega-3 fatty acids and cardiac arrhythmias: Prior studies and recommendations for future research. Circulation, Vol. 116, September 2, 2007, pp. 320-35