Do omega-3s help against cardiac arrhythmias?

Fish oil supplements have no demonstrable effect against cardiac arrhythmias. A large Cochrane meta-analysis of 30 randomised studies involving nearly 78,000 participants found virtually no difference compared with placebo. Fish oil also had little to no effect on total mortality or the total number of cardiovascular events.

There is even a serious warning: at high doses, omega-3 supplements increase the risk of atrial fibrillation, the most common cardiac arrhythmia. This applies to pure EPA supplements as well as to the EPA+DHA combination. The risk is dose-dependent: the higher the dose, the greater the risk¹. Earlier promising results have therefore not been confirmed in better-designed research -- in fact, they have been reversed.

The plant-based omega-3 fatty acid ALA, found for example in flaxseed, presents a slightly different picture. Two studies involving nearly 5,000 participants found a small indication of fewer cardiac arrhythmias. However, the absolute benefit is small: on average, 91 people need to be treated to prevent one case. The evidence is moderate and rests on only two studies, so this is not yet an established fact.

On the topic of sudden cardiac death, the picture is mixed. Two older randomised studies and animal research observed an anti-arrhythmic effect, but later studies did not broadly confirm this². Older observational data suggest a link between eating fish and lower rates of sudden cardiac death, but this is not a proven causal relationship³. On the basis of current evidence, fish oil supplements cannot be recommended for this purpose either.

If you genuinely want to reduce your risk of atrial fibrillation, focus on proven approaches: keeping blood pressure under control, losing weight, stopping alcohol and getting sleep apnoea treated⁴. Omega-3 supplements do not appear in that overview as an effective strategy.