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Is Fish Oil Linked to Heart Rhythm Changes?

People taking fish oil or purified EPA, a component of fish oil, appear more susceptible to heart rhythm changes called atrial fibrillation.
Is Fish Oil Linked to Heart Rhythm Changes?
Fish oil capsules, close-up

Could a supplement that people take for heart health actually lead to heart rhythm changes? Most people take fish oil with the expectation that it will lower their likelihood of a heart attack or stroke. Articles in the medical literature have been hinting at such a benefit for more than a decade (Current Vascular Pharmacology, Jan. 2008; Cardiology Reviews, Sep-Oct. 2010). But could omega-3 fatty acids found in fish oil trigger atrial fibrillation? One reader posed that question.

Does Fish Oil Lead to Heart Rhythm Changes?

Q. I recently learned of a 2005 Danish study that showed a correlation between atrial fibrillation and fish oil. My wife stopped taking 1.2 gm of fish oil daily and stopped fibrillating. On her doctor’s advice, she no longer has to take a drug for this problem.

Do you have any information that you can add to support a correlation between fish oil and fibrillation?

A. Your question intrigued us because research has looked at fish oil for preventing rather than causing atrial fibrillation, also known as Afib. Most of the fish oil trials have been inconclusive or shown no benefit for dangerous heart rhythm changes. However, more recent trials do suggest a connection between high doses of omega 3 fats and Afib.

Does the Dose of Fish Oil Make a Difference for Afib?

The Danish study you cited, (American Journal of Clinical Nutrition, Jan. 2005), concluded that fish consumption did not reduce the risk of atrial fibrillation. The data actually revealed a trend toward a higher risk of this rhythm abnormality among people taking more fish oil.

A later Danish study reported that people getting a moderate amount of fish oil from their diets were less likely to experience atrial fibrillation than those eating more or less fish (Europace, Nov. 2014).  The best dose provided about half as much omega-3 fat as your wife was taking.

A recent study of more than 8,000 people at high risk for heart attacks found that a highly purified component of fish oil, icosapent ethyl (Vascepa), reduced heart attacks and strokes (New England Journal of Medicine, Nov. 10, 2018). That is, 17.2 percent of those taking Vascepa had a cardiovascular complication compared to 22 percent of those taking a placebo. On the other hand, more people taking the Vascepa developed atrial fibrillation (3.1 percent compared to 2.1 percent), suggesting that the link is real.

Fish Oil Helped Dry Eyes but Triggered Afib:

Q. I have had atrial fibrillation (Afib) for 15 years. Recently, I read about a study of fish oil at Cedars-Sinai. Apparently, the combination of EPA and DHA can cause Afib if the dose is over 1 gram.

I was taking an over-the-counter product for dry eyes. I stopped the product and have had no AFib in over two months.

A. Fish oil has a good reputation for treating dry eyes. However, a placebo-controlled trial does not show that relieves dry eye symptoms more than olive oil (New England Journal of Medicine, May 3, 2018).

Some doctors recommend fish oil or prescribe icosapent ethyl (Vascepa) to reduce the risk of heart attacks (EClinical Medicine, Aug. 2021). A meta-analysis of 38 studies shows that such omega-3 acids can be helpful. On the other hand, EPA (eicosapentaenoic acid) alone increases the chance of Afib by about 35 percent. It may also raise the chance of bleeding, especially if taken with anticoagulants like apixaban (Eliquis) or warfarin (Coumadin).

Readers Report Their Experiences with Fish Oil and Heart Rhythm Changes:

Pat from Bellevue, WA, reported:

“About 6 years ago I began heart irregularities, I read that there are more cases of Afib in Norway than other places and that the high amount of salmon that is consumed was associated with too much Omega 3 from salmon. After quitting both eating salmon and fish oil capsules my heart returned to normal.

“After 6 months I ate a small piece of salmon and immediately fibrillated. The problem got worse even though I quit fish of any kind. I went to a cardiologist who suggested I needed heart ablation. The operation took 7 hours and I was Afib free for a year and a half. I tried a small piece of salmon and fibrillated for 2 days before it stopped. I have been Afib-free since then and do not eat any fatty fish. Cod and shellfish are not a problem.”

Susan in Seattle, WA, also found that fish oil can trigger heart rhythm changes:

“I, too, after many years taking fish oil for dry eye, suddenly started having this problem. I discovered the new fish oil contained Vitamin E, and that causes arrhythmia in me. As soon as I stopped taking that brand of fish oil, the Afib stopped. Check the ingredient label, also the inert ingredients.”

We suggest that anyone having difficulty with unexplained Afib might consider whether they are taking fish oil supplements that might be responsible. If you have a fish oil story of your own, please share it with us below.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies. .
  • Leaf A et al, "Fish oil fatty acids as cardiovascular drugs." Current Vascular Pharmacology, Jan. 2008. DOI: 10.2174/157016108783331286
  • Weitz D et al, "Fish oil for the treatment of cardiovascular disease." Cardiology Reviews, Sep-Oct. 2010. doi: 10.1097/CRD.0b013e3181ea0de0
  • Frost L & Vestergaard P, "n-3 Fatty acids consumed from fish and risk of atrial fibrillation or flutter: the Danish Diet, Cancer, and Health Study." American Journal of Clinical Nutrition, Jan. 2005. DOI: 10.1093/ajcn/81.1.50
  • Rix TA et al, "A U-shaped association between consumption of marine n-3 fatty acids and development of atrial fibrillation/atrial flutter-a Danish cohort study." Europace, Nov. 2014. DOI: 10.1093/europace/euu019
  • Bhatt DL et al, "Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia." New England Journal of Medicine, Nov. 10, 2018. DOI: 10.1056/NEJMoa1812792
  • Dry Eye Assessment and Management Study Research Group et al, "n-3 fatty acid supplementation for the treatment of dry eye disease." New England Journal of Medicine, May 3, 2018. DOI: 10.1056/NEJMoa1709691
  • Khan SU et al, "Effect of omega-3 fatty acids on cardiovascular outcomes: A systematic review and meta-analysis." EClinical Medicine, Aug. 2021. doi: 10.1016/j.eclinm.2021.100997
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