Atrial fibrillation (AF) is the most common cardiac arrhythmia (abnormal heart rhythm), with more than 2.3 million people affected in the U.S. It involves fibrillating (i.e., quivering) in the muscles of the two upper chambers (atria) of the heart.
AF is a symptom of underlying heart disease. It often becomes a chronic condition that may result in stroke, palpitations, fainting, chest pain, or congestive heart failure, and it leads to a small increase in the risk of death.
This cardiac condition can be treated with drugs... but they sometimes exacerbate AF or produce other cardiac arrhythmias.
Accordingly, researchers have been looking for ways to prevent AF from developing in the first place.
In some but not all studies, regular fish consumption has been shown to reduce the risk of AF.
(For a fuller exploration of the evidence, see “Omega-3s Yield Heart-Saving Effects Even in Small Amounts” and “Fish Oil Can’t Rescue the Sickest Cardiac Patients’ Heart Rhythms”.)
It’s been presumed that omega-3s are why eating fish seems to reduce the risk of cardiac arrhythmias, and there are sound physiological reasons why that makes sense.
Among other possible effects, omega-3s selectively quiet “hyper-excitable” heart muscle cells, which tend to trigger arrhythmias.
An epidemiological study from Finland supports the value of fish fat, and singles out one omega-3 fat in particular – DHA – as being the most beneficial.
Finnish study links higher omega-3 DHA blood levels to reduced AF risk
Researchers from the University of Kuopio in Finland wanted to look for any associations between omega-3 blood levels and the risk of AF (Virtanen JK et al. 2009).
They analyzed blood test data and medical records from 2,174 men aged 42 to 60 who participated in the Kuopio Ischemic Heart Disease Risk Factor Study from 1984 to 1989.
All of the men were free of AF at the start of the study, and provided blood samples upon their enrollment.
The researchers examined the men’s medical records an average of almost 18 years later, looking for any associations between omega-3 blood levels and a diagnosis of AF.
They grouped the men into four categories (quartiles), based on their blood levels of omega-3s.
After comparing the participants’ blood data with their medical records, the Finns found that the men with the highest omega-3 levels when the study began were 35 percent less likely to have been diagnosed with AF by the end of the study some 18 years later.
And the results held a real surprise. DHA outdoes EPA: Finding further bolsters DHA as key heart ally
People have been led to believe that of the two key omega-3s in fish oil – EPA and DHA – the most important one for cardiac health is EPA, based on its anti-inflammatory effects.
This assertion is scientifically unfounded – in fact, DHA appears as or more important than EPA – but has been exploited by makers of fish oil products that have been chemically manipulated to contain ratios of EPA to DHA far higher than those found in fish fat.
Further undermining the common “EPA is better” claim, the Finns’ analysis found no association between EPA blood levels and risk of AF.
Instead, only high blood levels of omega-3 DHA were associated with the very substantially reduced risk of AF.
The positive association between DHA levels and reduced risk of AF were strengthened further when the researchers excluded the 233 men who’d experienced a heart attack or congestive heart failure.
Interestingly, they found no associations between AF risk and levels of mercury or short-chain, plant-food-derived omega-3s.
This study is surely not the last word in omega-3s and cardiac arrhythmias.
But it reinforces the recommendation to eat two servings of fish per week, made by the American Heart Association and other expert bodies.
- Anand RG, Alkadri M, Lavie CJ, Milani RV. The role of fish oil in arrhythmia prevention. J Cardiopulm Rehabil Prev. 2008 Mar-Apr;28(2):92-8. Review.
- Cheng JW, Santoni F. 3.Omega-3 fatty acid: a role in the management of cardiac arrhythmias? J Altern Complement Med. 2008 Oct;14(8):965-74. Review.
- Lombardi F, Terranova P. Anti-arrhythmic properties of N-3 poly-unsaturated fatty acids (n-3 PUFA). Curr Med Chem. 2007;14(19):2070-80.
- Reiffel JA, McDonald A. Antiarrhythmic effects of omega-3 fatty acids. Am J Cardiol. 2006 Aug 21;98(4A):50i-60i. Epub 2006 May 26. Review.
- Virtanen JK, Mursu J, Voutilainen S, Tuomainen TP. Serum long-chain n-3 polyunsaturated fatty acids and risk of hospital diagnosis of atrial fibrillation in men. Circulation. 2009 Dec 8;120(23):2315-21. Epub 2009 Nov 23.