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Where Did The Idea That Omega-3s Cause Atrial Fibrillation Come From?

Author: Dr. Stephen Chaney 

You may have heard that omega-3s are potentially dangerous because they can cause atrial fibrillation, often referred to as AFib, which increases your risk of stroke and heart failure.

You may have heard it from your doctor. You may have read about it online. The source of your information doesn’t matter. It sounds scary. You are probably taking omega-3 supplements to reduce your risk of heart disease. But what if they had the opposite effect? What if they increased your risk?

So, in today’s issue of “Health Tips From The Professor” I will ask three questions.

• Is it true?

• If it’s true, does it apply to you?

• If it applies to you, what is your risk?

But, before I answer those questions, I want to look at where the idea that omega-3s can cause atrial fibrillation came from.

Where Did The Idea That Omega-3s Cause Atrial Fibrillation Come From? 

The idea that omega-3s might cause atrial fibrillation originated when it was reported as a side effect in a couple of clinical studies using high-dose, ultra-pure EPA (more about those studies below).

Once those studies were published, the medical community did the responsible thing and investigated the risk further. Two meta-analyses of studies looking at omega-3 supplementation and cardiovascular outcomes appeared to confirm that omega-3 supplementation increased the risk of atrial fibrillation by around 25%.

Case closed, you might say. These results were widely reported in medical journals and by medical societies. They were repeated over and over until they became generally accepted as true.

But further analysis revealed that both meta-analyses had methodological flaws. Without going into detail, the two flaws that matter to me are:

• Both meta-analyses were very small. One included only 7 studies and the second only 8.

• Both were highly influenced by two very large studies using the pharmaceutical drug Vascepa. Vascepa is an ultrapure form EPA and is administered at an extremely high dose (4 gm/day).

• • That’s important because while ultra-purity is required for pharmaceuticals, it is not always good for supplements.

• • In the case of omega-3s, EPA is not the only naturally occurring omega-3. There is a family of omega-3s, and each provides ubique benefits. Unfortunately, when you take a high dose of a single omega-3, it interferes with the absorption of the other omega-3s.

In addition, two subsequent studies have called into question the conclusions of the two original meta-analyses.

• A third meta-analysis reported that the increased risk of atrial fibrillation might be restricted to high-dose omega-3 studies.

• Another meta-analysis reported that blood levels of omega-3s were inversely associated with atrial fibrillation. [This meta-analysis did not include any high-dose omega-3 studies.]

So, the authors of the current study (NR Abuknesha et al, Circulation: Arrythmia and Electrophysiology, 19e014785, 2026) decided to investigate the association between omega-3 supplementation and atrial fibrillation using a much larger collection of clinical studies.

Their hypothesis was that the risk of atrial fibrillation would depend on both omega-3 dose and background cardiovascular risk status. So, they segmented the risk of atrial fibrillation by omega-3 dose and heart disease risk.

How Was This Study Done? 

The investigators combined data from 35 randomized clinical trials with 114,592 participants in omega-3 supplementation studies. Most of the studies were double-blind, placebo-controlled trials, but a few compared omega-3 supplementation with standard of care treatment.

To be included in this meta-analysis the studies had to:

• Use EPA+DHA doses of ≥500 mg/day.

• Last for at least 12 months (The duration of the studies ranged from 12 to 89 months).

• Enroll patients aged ≥50 years (The ages ranged from 53 to 78, average = 66). This requirement was added because 50 is usually the age at which atrial fibrillation is first diagnosed.

Patients were excluded from the data analysis if they had been diagnosed with atrial fibrillation prior to the study.

The data analysis divided participants according to:

• Omega-3 dose (less than 1,500 mg/day or ≥1,500 mg/day.

• Heart disease risk with high-risk patients with high risk defined as diagnosis of cardiovascular disease or the presence of multiple cardiovascular risk factors.

Do Omega-3s Cause Atrial Fibrillation?

The study divided the 114,592 participants into 4 groups based on heart disease risk and dosage of omega-3s (<1,500 mg/day and ≥1,500 mg/day).

• The study reported a 43% increased risk of atrial fibrillation in the high risk/high dose group.

• In contrast, the study found no statistically significant risk for developing atrial fibrillation in the low risk/low dose, low risk/high dose, and high risk/low dose groups.

• And when compared to the high risk/high dose group, the other groups experienced a 28% reduction in atrial fibrillation risk.

While the 43% increased risk of developing atrial fibrillation in the high risk/high dose group sounds scary, it is an increase in relative risk, not absolute risk.

• That is important because the baseline risk of developing atrial fibrillation in the group at high risk of heart disease was only 1.9%. That means a 43% increase in relative risk only raised the risk to 2.7%, which represents an absolute increase in risk of 0.8%!

The authors concluded, “This meta-analysis demonstrates a clear dose-dependent association between omega-3 supplementation and atrial fibrillation risk. Importantly, low-dose omega-3 supplementation does not appear to increase atrial fibrillation risk, even among patients at high cardiovascular risk, providing reassurance regarding the safety of commonly used nutritional doses.”

“In contrast, high doses of omega-3s (typically from pharmacological products) administered to patients at high cardiovascular risk were associated with a ~40% to 45% increase in atrial fibrillation risk, although the absolute risk increase is modest (0.8%).”

“These findings suggest that omega-3 supplementation providing <1,500 mg/day (and possibly up to 2,400 mg/day) can be used safely with respect to atrial fibrillation risk, whereas doses exceeding 3,000 mg/day in high-risk cardiovascular populations may warrant caution.”

“Given that elevated blood omega-3 levels…are associated with reduced atherosclerotic risk and other favorable outcomes, the small atrial fibrillation [risk] in high-risk heart disease populations should be weighed against the substantial cardiovascular benefits when making treatment decisions.”

The authors elaborated on that last point in the discussion section by saying, “For example, in REDUCE-IT [the clinical study of the drug Vascepa], the 1.0% absolute increase in atrial fibrillation hospitalization with 4 g/day of EPA was offset by a 4.8% absolute reduction in major adverse cardiovascular events, a trade-off that strongly favors treatment [with omega-3s] given that [major cardiovascular events] carry far greater clinical consequences than increased risk for new-onset atrial fibrillation.”

What Does This Mean For You?

The take home lesson is clear. You can ignore the hype. Fears of omega-3 supplementation causing atrial fibrillation are overblown. A major meta-analysis of 35 clinical studies with 114,592 participants showed that:

• If you have no history of heart disease and are at low risk for developing heart disease, even high-dose omega-3 supplements do not increase your risk of developing atrial fibrillation.

• If you already have heart disease or are at a high risk of developing heart disease, low dose omega-3 supplements do not increase atrial fibrillation risk.

• • The data from this study shows that doses below 1,500 mg/day of EPA+DHA are clearly safe. A more detailed analysis of their data led the authors to say that doses below 2,400 mg/day are probably safe.

• If you have heart disease or are at high risk of developing heart disease high-dose omega-3 supplements may increase your risk of atrial fibrillation.

• • The cutoff point for high-dose EPA+DHA supplements was ≥1,500 mg/day. But a more detailed analysis of their data led the authors to say that doses above 3,000 mg/day should be avoided if you are at high risk of heart disease.

• The authors also said that even at 4,000 mg/day the absolute increase in risk was only around 1%, and the benefits of high-dose EPA supplementation outweighed the slight increase in atrial fibrillation risk.

The bottom line is that if you have heart disease or are in the high-risk category and are considering high-dose omega-3 supplementation (>3,000 mg/day), you should have a risk-benefit discussion with your doctor.

While the authors of this study did not address it, my recommendation is that if you currently have atrial fibrillation, you should also have a discussion with your doctor before beginning omega-3 supplementation. The risk is small, but you may want to monitor your atrial fibrillation and modify your omega-3 supplementation if it worsens.

The Bottom Line

Some earlier studies suggested that omega-3 supplementation may increase the risk of atrial fibrillation (AFib), and the findings of these studies have been reported so often that they are generally accepted as true.

However, a new meta-analysis of 35 randomized clinical trials with 114,592 patients has challenged this belief. This study found:

• The association between omega-3 supplementation and atrial fibrillation only occurs in patients with heart disease or at high risk of developing heart disease and only at high doses (>3,000 mg/day) of omega-3s.

• And the increased risk is very small (absolute risk = 0.8%) in this group.

For more details on this study and what it means for you, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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My posts and “Health Tips From the Professor” articles carefully avoid claims about any brand of supplement or manufacturer of supplements. However, I am often asked by representatives of supplement companies if they can share them with their customers.

My answer is, “Yes, as long as you share only the article without any additions or alterations. In particular, you should avoid adding any mention of your company or your company’s products. If you were to do that, you could be making what the FTC and FDA consider a “misleading health claim” that could result in legal action against you and the company you represent.

For more detail about FTC regulations for health claims, see this link.

https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance

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About The Author 

Dr. Chaney has a BS in Chemistry from Duke University and a PhD in Biochemistry from UCLA. He is Professor Emeritus from the University of North Carolina where he taught biochemistry and nutrition to medical and dental students for 40 years.  Dr. Chaney won numerous teaching awards at UNC, including the Academy of Educators “Excellence in Teaching Lifetime Achievement Award”. Dr Chaney also ran an active cancer research program at UNC and published over 100 scientific articles and reviews in peer-reviewed scientific journals. In addition, he authored two chapters on nutrition in one of the leading Biochemistry textbooks for medical students.

Since retiring from the University of North Carolina, he has been writing a weekly health blog called “Health Tips From the Professor”. He has also written two best-selling books, “Slaying the Food Myths” and “Slaying the Supplement Myths”. And most recently he has created an online lifestyle change course, “Create Your Personal Health Zone”. For more information visit https://chaneyhealth.com.

For the past 54 years Dr. Chaney and his wife Suzanne have been helping people improve their health holistically through a combination of good diet, exercise, weight control and appropriate supplementation.