#367 Latest Research on Atrial Fibrillation and Fish Oil Supplements: What You Need to Know

Latest Research on Atrial Fibrillation and Fish Oil Supplements: What You Need to Know

Since I last wrote about atrial fibrillation and fish oil supplements 3 years ago (here), there have been even more studies showing an increased risk of AFib and strokes from fish oil supplements. This latest study, published in the prestigious British Medical Journal, on the effects of taking fish oil in 415,737 patients especially caught my attention. Needless to say, I personally stopped taking fish oil supplements a few years ago when I started developing palpitations (the palpitations went away when I stopped taking fish oil), and I have been warning all my patients taking fish oil of this potential AFib risk.

Why are Omega-3s Important?

Omega-3 fatty acids are essential fats, meaning our bodies cannot produce them, and we must obtain them from our diet. The three main types of omega-3s are:

1. ALA (alpha-linolenic acid): Found in plant oils such as flax seeds, chia seeds, and walnuts.

2. EPA (eicosapentaenoic acid): Found in fish and other seafood.

3. DHA (docosahexaenoic acid): Also found in fish and other seafood.

Omega-3s are vital for maintaining the structure and function of cell membranes, supporting brain health, and reducing inflammation. They have been extensively studied for their role in cardiovascular health.

Fish Oil and Heart Health

Fish oil supplements are particularly rich in EPA and DHA, which have been shown to offer several cardiovascular benefits:

1. Lowering Triglycerides: High levels of triglycerides in the blood are a known risk factor for heart disease. Fish oil has been shown to effectively lower triglyceride levels, thus helping to reduce this risk.

2. Preventing Heart Attacks: Omega-3s contribute to heart health by reducing inflammation, decreasing blood clotting, and stabilizing heart rhythms. These effects collectively help in lowering the risk of heart attacks.

The Dark Side of Fisk Oil: Atrial Fibrillation and Strokes

Despite these benefits, recent research has pointed to potential risks associated with fish oil supplements, particularly concerning atrial fibrillation (AFib) and stroke.

1. Atrial Fibrillation: AF is a condition characterized by irregular and often rapid heart rate, which can increase the risk of stroke and heart failure. Some studies have found an association between high doses of fish oil and an increased risk of developing AFib. The exact mechanisms are not fully understood, but it is speculated that this concentrated dose of the omega-3 supplement might alter the electrical activity in the heart, leading to arrhythmias.

2. Stroke: While omega-3s have anticoagulant properties that can be beneficial in preventing heart attacks, they may also increase the risk of bleeding, including hemorrhagic stroke. Additionally, there is some evidence suggesting that fish oil supplements might slightly increase the risk of ischemic stroke.

Latest Findings on Fish Oil and Atrial Fibrillation

A recent study published in the prestigious British Journal of Medicine explored the impact of fish oil supplements on various stages of cardiovascular disease. This extensive study included 415,737 participants aged 40-69 years from the UK Biobank. The researchers examined the role of fish oil supplements in people who hadn’t developed cardiovascular disease versus those who already had cardiovascular disease.

For individuals without any cardiovascular disease, the study found that regular use of fish oil supplements was associated with an increased risk of developing atrial fibrillation and stroke. Specifically, for those healthy people taking fish oil they had a 13% increased risk of developing atrial fibrillation and a 5% increased risk of stroke from taking fish oil.

Interestingly, the study also highlighted that for people with pre-existing cardiovascular disease, fish oil supplements had beneficial effects. Thus, for these people who already had heart problems, taking fish oil decreased their risk of a heart attack by 15% and decreased their risk of dying from heart failure by 9%. This suggests that for people who already have heart disease that fish oil might be beneficial.

The study concluded that while regular use of fish oil supplements might increase the risk of atrial fibrillation and stroke among the healthy general population, they could be beneficial for individuals with existing cardiovascular disease. Of course, further research is needed to understand the mechanisms behind these effects and to develop clear guidelines on the use of fish oil supplements for cardiovascular health.

Balancing the Benefits and Risks

Given the mixed evidence, how should one approach fish oil supplementation?

1. Consult with a Healthcare Provider: Before starting any supplement, it’s crucial to discuss it with your healthcare provider, especially if you have underlying health conditions or are taking other medications.

2. Dietary Sources: Consider getting omega-3s from dietary sources such as fatty fish (salmon, mackerel, sardines) rather than supplements. This approach provides all the benefits of omega-3s along as well as the other nutrients found in whole foods without the risk. In addition to fatty fish, consider adding walnuts, chia seeds, or flax seeds which are all very high in the plant-based omega-3s. Personally, I have replaced fish oil supplements with wild fatty fish each week (salmon) and a large daily dose of chia and flax seeds.

3. Moderation: If you choose to take fish oil supplements, moderation is key. Studies suggest that the higher the fish oil dose the higher the atrial fibrillation risk.

4. Stay Informed: Keep up with the latest research and guidelines regarding omega-3s and fish oil supplements. Scientific understanding evolves, and staying informed can help you make the best decisions for your health.


Omega-3s from food offer significant health benefits, particularly in lowering triglycerides and reducing the risk of heart attacks. However, the potential risks, including an increased likelihood of atrial fibrillation and stroke, necessitate a very cautious and informed approach to taking fish oil supplements. Balancing dietary sources of omega-3s with the cautious use of supplements, under the guidance of a healthcare provider, can help maximize benefits while minimizing risks.

Always remember, your health is a holistic picture, and supplements may just one piece of the puzzle. Eating a healthy balanced diet, maintaining a healthy lifestyle, and consulting with healthcare professionals are the best strategies for heart health and overall well-being.


The information provided in this article is intended for general informational purposes only and does not constitute medical advice. Always consult with a healthcare provider before starting or changing any supplement regimen, especially if you have underlying health conditions or are taking other medications. The potential benefits and risks of fish oil supplements can vary based on individual health profiles and conditions. The findings discussed are based on current research and may evolve as new studies emerge.

About the Photo

I took this photo yesterday while riding the Mid-Mountain Trail in Park City for the first time this year. The runoff water from the melting snow was gushing down the mountain with full force. Some parts of the trail were still covered in snow, and many trees had fallen across the path since I last rode it in the fall. Despite these obstacles, I was the only person on the trail, and it was an epic bike ride on a warm and sunny late spring day.

Disclaimer Policy: This website is intended to give general information and does not provide medical advice. This website does not create a doctor-patient relationship between you and Dr. John Day. If you have a medical problem, immediately contact your healthcare provider. Information on this website is not intended to diagnose or treat any condition. Dr. John Day is not responsible for any losses, damages or claims that may result from your medical decisions.

  1. VERY important question: were all the fish oil supplements used in theses studies TESTED for the levels of heavy metals present? If this factor is not controlled for, it will skew results. Also, is there a plausible mechanism by which PURE, uncontaminated fish oils could cause the increased cardiovascular risk?

  2. I have followed your news letter for a couple of years now. I had an ablation in Dec 23. I have had 2 atrial fib episodes since and 19 episodes of tachycardia. My centre wants me to undergo another ablation but they will not agree to use the pulse field for re-dos. I will not agree to a radio-frequency again as I understand it carries certain risks that pulse-field does not. Is there a reason once you have had a radio-frequency that you cannot be redone with pulse field?