Key Points
- Omega-3 fatty acids from food, particularly oily fish like salmon, are consistently associated with cardiovascular benefit and remain an important part of a heart-healthy diet.
- Fish oil supplements are a different story. A major 2024 study found that for people without pre-existing heart disease, regular supplementation was associated with a modestly increased risk of atrial fibrillation and stroke.
- The AF risk appears to be dose-dependent, higher doses (over 1 gram per day) carry a more meaningful signal, while low-dose supplementation shows a much smaller effect.
- For people with existing cardiovascular conditions or elevated triglycerides, the picture is more nuanced and prescription-strength omega-3 therapy may still have a role, discuss this with your doctor.
- The best approach for most people is to get omega-3 from whole food sources rather than supplements.
Fish oil is one of the most widely taken supplements in the world. For years, the assumption was straightforward, omega-3 fatty acids are good for the heart, so taking more of them in capsule form must be a sensible precaution. The science has become considerably more complicated.
Recent research, including a significant 2024 study published in the BMJ, has raised genuine questions about whether fish oil supplements benefit everyone, or whether they may actually carry risks for certain groups. This article unpacks what the evidence shows, what it means for you, and where that leaves the salmon on your plate.
What are omega-3 fatty acids?
Omega-3 fatty acids are a type of polyunsaturated fat found naturally in oily fish, certain nuts and seeds, and plant oils. The two most studied forms in cardiovascular research, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), are found predominantly in fatty fish such as salmon, mackerel, sardines, and trout.
These fatty acids play important roles in reducing inflammation, supporting healthy cell membranes, and modulating heart rhythm and blood vessel function. The evidence for their benefit when consumed as part of a whole-food diet is well established. The question is whether the same benefits apply when they are extracted and concentrated into a supplement, and the answer, it turns out, is not always.
What did the 2024 BMJ study find?
The study, conducted as part of the UK Biobank project, followed 415,737 participants aged 40 to 69 over more than a decade. It examined the impact of regular fish oil supplement use on three outcomes, atrial fibrillation, major adverse cardiovascular events, and mortality.
participants followed for over a decade in the UK Biobank study, one of the largest analyses of fish oil supplement use and cardiovascular outcomes
The findings were nuanced and depended significantly on whether participants had pre-existing heart disease.
| Group | Finding |
|---|---|
| People without pre-existing heart disease | 13% higher risk of atrial fibrillation and 5% greater risk of stroke with regular fish oil supplement use |
| Women without pre-existing heart disease | 6% higher likelihood of heart attack, stroke, or heart failure |
| People with existing cardiovascular conditions | 15% lower risk of progression from AF to more serious cardiac events, and from heart failure to death |
This is an observational study, it cannot prove that fish oil supplements directly caused these outcomes. Factors such as dosage, formulation, and individual lifestyle were not fully accounted for, and self-reported supplement use introduces some uncertainty. These limitations are important to acknowledge. But the findings are consistent with a growing body of evidence and deserve to be taken seriously.
Does dose matter?
Increasingly, yes. More recent research has helped refine the picture considerably. The AF risk signal appears to be closely tied to dose, higher doses appear to carry a more meaningful risk, while lower doses show a much smaller effect.
Research from the Cedars-Sinai Smidt Heart Institute found that taking more than one gram of fish oil per day may meaningfully increase the risk of atrial fibrillation. For those taking one gram or less, the risk appears relatively small. And importantly, separate analyses of blood omega-3 levels, reflecting what people get from their diet rather than supplements, have found the opposite relationship: higher dietary omega-3 intake is actually associated with lower AF risk.
This distinction matters enormously. It suggests the issue is not omega-3 itself, but how it is delivered, in concentrated supplement form versus as part of a whole food.
What about prescription omega-3 therapy?
Prescription-strength omega-3 medications, used specifically to treat very high triglyceride levels, are a separate category from over-the-counter supplements. Some formulations, particularly highly purified EPA preparations, have shown meaningful cardiovascular benefit in specific high-risk populations in randomised controlled trials. These are prescribed medications with defined indications, not supplements taken on a general wellness basis.
If you have been prescribed an omega-3 medication by your doctor for a specific clinical reason, this is different from taking over-the-counter fish oil capsules. Do not stop a prescribed medication without discussing it with your doctor first.
My advice to patients is consistent, get your omega-3 from food wherever possible. A couple of servings of salmon a week, good olive oil, a handful of walnuts. If your triglycerides are significantly elevated, that is a conversation to have with your cardiologist about whether prescription therapy is appropriate for you.
What about people with existing heart conditions?
The BMJ study’s findings for this group were more encouraging, suggesting a possible protective effect in preventing disease progression. However, this does not mean that everyone with heart disease should self-prescribe fish oil supplements. The appropriate use of omega-3 therapy in this setting depends on your specific condition, the dose being considered, and your overall management plan. This is a decision to make with your cardiologist, not independently.
Where does this leave the supplement aisle?
Fish oil supplements are one of the most purchased supplements globally, often taken on the basis that they are natural and therefore harmless. The emerging evidence suggests that for most healthy people without cardiovascular disease, there is little clear benefit from supplementation and a possible, dose-dependent risk that warrants caution.
This does not mean omega-3 is harmful, it means the supplement form is not equivalent to the food form, and the dose matters more than most people realise. A capsule delivering two to four grams of concentrated omega-3 daily is a pharmacological dose, not a dietary one.
Practical steps
| Situation | Practical approach |
|---|---|
| Generally healthy, no heart disease | Focus on dietary omega-3, oily fish twice a week, olive oil, nuts and seeds. No strong case for supplements. |
| Taking fish oil supplements currently | Review with your GP. If you continue, keep the dose at or below 1 gram per day and discuss your AF risk. |
| High triglycerides | Discuss prescription omega-3 options with your doctor, not the same as over-the-counter supplements. |
| Existing heart disease | Do not self-prescribe. Discuss omega-3 therapy with your cardiologist in the context of your full treatment plan. |
Questions to Ask Your Doctor
If you take fish oil supplements or are considering them, here are some useful questions to raise:
Questions worth asking
- I currently take fish oil supplements, given the recent evidence on AF risk, should I continue and at what dose?
- My triglycerides are elevated, is prescription omega-3 therapy appropriate for me, and how does it differ from over-the-counter fish oil?
- I have atrial fibrillation, does this change the advice around fish oil supplements in my case?
- What dietary changes would make the biggest difference to my omega-3 levels without needing a supplement?
Conclusion
The story of fish oil supplements is a useful reminder that natural does not automatically mean safe, and that dose matters enormously. The evidence from the 2024 BMJ study and subsequent research paints a nuanced picture, omega-3 from food is beneficial, high-dose supplementation in people without heart disease carries real questions, and prescription-strength therapy in specific clinical settings remains a separate and legitimate option.
For most people, the most evidence-based approach is also the most enjoyable one, a couple of servings of oily fish each week, alongside the other elements of a Mediterranean-style diet. If you are currently taking fish oil supplements and unsure whether to continue, a brief conversation with your GP is the right next step.
As the research continues to evolve, we will update this article to reflect the latest evidence. That is the nature of good science, and good cardiology.
Free Resources
Our Heart Glossary explains terms like atrial fibrillation, triglycerides, EPA, DHA, and omega-3 in plain language.
