Fish oil and heart health: Is it helping or harming your heart?

Recent research has raised an important question: could fish oil supplements increase the risk of heart rhythm problems like atrial fibrillation (AF)?

The Centre for Healthy Futures (CHEF) at Torrens University Australia is interested in understanding how fish oil interacts at the cellular level and which gene pathways might influence its effects on heart health. While fish oil may still be beneficial for some people, new evidence suggests that dose matters — and that keeping fish oil intake under 1g per day may be the safest bet for most people.

Atrial fibrillation: A risk worth paying attention to

Atrial fibrillation is the most common heart rhythm disorder, affecting millions of people worldwide. It happens when the heart’s electrical system malfunctions, causing an irregular and often rapid heartbeat.

AF increases the risk of stroke, heart failure, and sudden death. Patients with AF often need to take blood thinners to prevent dangerous blood clots, which adds another layer of risk when considering supplements like fish oil.

While omega-3s were once thought to help prevent arrhythmias, recent studies suggest they might actually trigger AF in some people, especially at high doses.

The evolving science on omega-3s and heart health

There’s no doubt that omega-3 fatty acids - found in fatty fishes like salmon, sardines, and mackerel are essential for heart and brain health. But when it comes to fish oil supplements, the story isn’t so simple.

Here’s what recent large clinical trials are telling us:

The OMEMI Trial (2021)

This trial found that in elderly heart attack survivors, omega-3 supplements did not reduce major cardiovascular events post-heart attack and were associated with a numerical increase in developing atrial fibrillation.

However, a secondary analysis of the data showed greater increases in eicosapentaenoic acid (EPA) were associated with lower risk of major adverse cardiac events and higher risk of new-onset AF remained. These data suggest that the cardiovascular effects of increasing omega-3 levels through supplements are complex, involving both potential benefits and harm.

The REDUCE-IT Trial (2018-2022)

In this trial, a purified fish oil supplement (icosapent ethyl, 4g/day) lowered cardiovascular events and stroke in those admitted for AF but also led to more hospitalisations for atrial fibrillation. This increased risk was observed primarily in patients with a prior history of atrial fibrillation.

A 2021 Meta-Analysis in Circulation

A review of multiple studies found that omega-3 supplementation was linked to a higher risk of atrial fibrillation, and higher doses (>1g/day) carried greater risk.

The UK Biobank Study (2022)

A study of 468,000 people found that habitual fish oil users had a higher rate of atrial fibrillation, even if they didn’t have genetic risk factors for it.

These findings don’t mean that fish oil is bad for everyone, but they do suggest that taking too much might not be a good idea.

Could your genes play a role in how fish oil affects you?

CHEF also suspect that genetic factors might determine how someone’s heart responds to omega-3s. While CHEF is not yet conducting this research, we’re interested in exploring which gene pathways might interact with fish oil to influence cardiovascular health.

Here are some genetic pathways that could be relevant:

Chronic dosing of fish oil in rabbits alters ion channel gene expression

Variations in these genes influence cardiac electrical activity and may determine whether omega-3s help stabilize or disrupt heart rhythm.

Inflammation and immune response genes

While omega-3s usually reduce inflammation, certain genetic variations might cause pro-inflammatory effects in some individuals.

Nervous system regulation genes

Omega-3s can increase heart rate variability, which is beneficial for most people but may trigger AF in those with specific genetic profiles.

These genetic interactions could help explain why omega-3s benefit some people but increase AF risk in others.

Should you still take fish oil?

With all this new research, you might be wondering: Should I keep taking fish oil?

Here’s what the current evidence suggests:

✓ Eat fatty fish instead of relying on supplements. If you eat fatty fish twice a week, you’re already getting plenty of heart-healthy omega-3s — no supplements needed.

✓ Keep fish oil supplements under 1g per day. Research suggests that higher doses (above 1g/day) may increase AF risk, so it’s best to stay on the lower end unless directed otherwise by a doctor.

✓ If you have high triglycerides, prescription icosapent ethyl (Vascepa) might help - but talk to your doctor about AF risk first.

✓ For general heart health, focus on a balanced diet rich in whole food sources of omega-3s rather than relying on supplements.

⚠ If you have a history of atrial fibrillation, be cautious. High-dose fish oil may not be safe for you.

How might fish oil affect heart rhythm at the cellular level?

CHEF is planning to explore how fish oil interacts with cellular mechanisms that regulate heart function.

Understanding these cellular-level interactions could explain why some people benefit from fish oil while others experience negative effects like AF.

The future of omega-3 research at CHEF

There is still a lot to learn about how fish oil affects heart health at the cellular and genetic level. CHEF is considering future research into:

• How omega-3s interact with heart cells to influence electrical activity.
• Whether specific gene pathways determine individual responses to fish oil.
• How personalised nutrition can guide safer, more effective cardiovascular health strategies.

For now, the best advice? If you’re taking fish oil, keep your dose under 1g per day — especially if you’re at risk for atrial fibrillation. And as always, talk to your doctor before making any major supplement changes.

Want to stay updated on the latest in heart health research?

CHEF is closely following new developments in omega-3s, cellular mechanisms, and heart health. If you’re interested in cardiovascular research or considering a PhD in this field, we’d love to hear from you.

For media inquiries or interviews with our heart health experts, email media.enquiries@torrens.edu.au.