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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 at least 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? That is the question one reader posed.

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 so far 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.

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.

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 A-fib 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 A-fib 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 A-Fib 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 A Fib 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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  1. John

    I was not taking any supplements until my paroxysmal AF hit me in Jan 2010. After many months I found the onset of AF occurred after eating and this was typified by symptoms similar to IBS and Coeliac Disease. I consulted a Nutritionist who initially put me on a nutrition plan starting with a probiotic and later expanded the plan to exclude gluten, wheat and oats. The plan then continued to be widened. She also advised me to take CoQ10 in capsule form and 5 ml of Arctic Cod Liver Oil a day. This does not contain Vitamin E, it contains Vitamin A and D only along with a range of Omega3 oils. Result only one, 5 hour episode of AF (due to sleeping on my left side) in 3 and half years. My medication for AF is Warfarin and Bisoprolol. I am also taking statins and BP medication.

  2. Veta
    North Carolina

    In 1995,when I was 45 years old, my brother who is an Internal Medicine MD, recommended that I take fish oil for my frequent PVC arrhythmia. So I took 3000 mg daily, and this stopped my premature ventricular beats. I continue to take the fish oil at 68 years old, with no arrhythmia.

  3. SUSAN

    The Vascepa is highly flawed since the placebo was a mineral oil capsule. The study actually compared Vascepa to mineral oil, not a true placebo. Read the study. This is just another way for Big Pharma to manipulate the data and public into paying $$$$$ for something a plant based diet can accomplish at a fraction of the cost.

  4. Jane Thompson

    I just received an order of Pumpkin seed oil. Is this oil similar to fish oil, and negative for atrial fib?

  5. Brian Voris
    San Miguel de Allende, MX

    I take flax seed oil which is also a source of omega 3, is there any information as to the effect of this on afib? I had an afib incident 5 years ago and take a beta blocker and a baby asprin in response.

    • Carol

      I take ground flax each day. Wonder if that could cause a-fib?

  6. John

    Been taking fish oil for years. Started taking salmon oil couple months ago. Started having heart palpitations. Cardio Dr. Did ultrasound on heart and other tests. No problems found. Think I’ll back off salmon oil and see if palpations subside.

  7. Evelyn
    Lilburn ga

    I was diagnosed with a fib last year. After every test the doctor could think of could not tell me why I had it. I was 79 at the time and was told it’s just an old age problem.. The only medication
    Taking was Lisinopril.

  8. Aya

    Thanks for the info. We have to closely monitor our bodies. Fish oil works for me. I don’t eat much salmon.

    • Cari

      Did you get a metabolic panel drawn? Maybe your electrolytes are low from the lisinopril. Just a thought.

  9. John
    Tamil Nadu

    It is unrelated to the above – but re: fish oil.
    In my case, fish oil consumption, 6000mg clearly and sharply cleared symptoms of anxiety and uneasiness. Thereafter, there was no change in mood/feeling after reducing the amount to 3000mg daily. This was five years ago.

  10. Marje

    My husband has taken fish oil for almost 15 years after his first heart attack 20 years ago. He had 2 more attacks 10 years ago plus a stroke. He will not eat a proper diet. He is now 85 – so I think it must be the fish oil that’s helping. He does not take statins and does not have high blood pressure.

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