AARHUS, DENMARK. There is impressive evidence that fish oils (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) can materially reduce the risk of sudden cardiac death (cardiac arrest). Researchers at the University of Washington found that men and women who consumed fatty fish just once a week reduced their risk of cardiac arrest by 50%. They believe that fatty fish consumption increases the levels of EPA and DHA in the membranes of red blood cells, which in turn, reduces platelet aggregation and the risk of fatal ventricular arrhythmias. Other researchers have confirmed the protective effect of fish oils against ventricular fibrillation, but very few, if any, studies have investigated the association between fish/fish oil intake and the development of atrial fibrillation.
A group of Danish researchers recently set out to fill in this gap in our knowledge. Their study included 22,528 men and 25,421 women (average age of 56 years) who were free of endocrine and cardiovascular diseases at baseline. All participants completed a detailed semi-quantitative food- and drink-frequency questionnaire and were then followed for an average of 5.7 years. At the end of the follow-up period 374 men (1.7%) and 182 women (0.7%) had been diagnosed with either atrial fibrillation or atrial flutter. About 10% of all participants were being treated for hypertension. Somewhat surprisingly, the researchers found that participants with a high consumption of fatty fish (herring, mackerel, sardines, trout, and salmon) had a significantly higher incidence of new-onset atrial fibrillation than did participants who rarely or never ate oily fish. After adjusting for age, gender, height, BMI, smoking, alcohol consumption, total daily energy intake, systolic blood pressure, treatment for hypertension, cholesterol level, and level of education, the researchers concluded that participants whose daily fish oil intake averaged 1290 mg had a 34% greater risk of developing AF than did those whose intake averaged only 160 mg/day. The difference was statistically significant (p=0.006). The researchers point out that the lack of an observed beneficial effect could have been because the consumption of fish oil was insufficient to prevent arrhythmias. They also say, "We cannot exclude the possibilities that fish oil may prevent the development of atrial fibrillation in patients with symptomatic heart disease or that fish oil may prevent relapses of atrial fibrillation in patients with paroxysmal atrial fibrillation."
Finally, they point out that they did not collect information regarding the use of fish oil supplements and also emphasize that they do not know whether fish oil would have a protective effect against the development of AF in populations with a low intake of fatty fish (such as the United States). Their overall conclusion was that, "Consumption of omega-3 fatty acids from fish is not associated with a reduction in the risk of developing atrial fibrillation or flutter."
Frost, L and Vestergaard, P. n-3 fatty acids consumed from fish and risk of atrial fibrillation or flutter: the Danish Diet, Cancer, and Health Study. American Journal of Clinical Nutrition, Vol. 81, January 2005, pp. 5-54