Most physicians agree that eating fish is good for the heart. There is less consensus about fish oil supplements. These are among the most popular supplements on drugstore shelves. People take them to promote heart health, ease joint pain and relieve dry eyes. The value of omega-3 fatty acids from fish oil has been controversial for years, however. New research suggests that it can increase the risk of atrial fibrillation.
Many health professionals believe that this dietary supplement is worthless. An analysis of ten clinical trials concluded that fish oil did not protect people with heart disease (JAMA Cardiology, March, 2018). The authors suggested that people with heart disease should not bother with fish oil. Many nutrition experts were quick to write off this dietary supplement.
What Does Science Say about Fish Oil?
Results of a large randomized placebo-controlled trial of fish oil were published in the New England Journal of Medicine (online Nov. 10, 2018).
The conclusions:
“Supplementation with n-3 [omega-3] fatty acids did not result in a lower incidence of major cardiovascular events or cancer than placebo.”
That sounds like the 1 gram of high-quality fish oil per day that half of the more than 25,000 volunteers took was pretty much of a dud. (The study used a product called Omacor and a look-alike placebo.) However, if you focus just on heart attacks or, even more important, fatal heart attacks, the data indicate that fish oil actually did offer benefit.
Fewer People Taking Fish Oil Had Heart Attacks:
Among the secondary end points were heart attacks, which were 28 percent less common among people taking fish oil. These participants were also only half as likely to suffer fatal heart attacks as people taking placebo. Those who got the most benefit were those who ate fish infrequently. Analysts warn, however, that secondary end points may be unreliable and need to be interpreted with caution.
A Study of Vascepa:
Another article published in the same issue of the New England Journal of Medicine presented results of a trial of a medication, icosapent ethyl, that is closely related to fish oil. Fish oil contains both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Icosapent ethyl (Vascepa) is a purified form of EPA only.
The REDUCE-IT trial had more than 8,000 volunteers taking either Vascepa or placebo. These people were at high risk because they had high triglycerides despite taking statins. Many of them also had heart disease.
In this study, 17 percent of the patients on Vascepa had a cardiovascular complication, compared to 22 percent of those on placebo. During the nearly five years of follow-up, 4.3 percent of those taking Vascepa died from cardiovascular causes compared to 5.2 percent of those on placebo. The difference is about 9 patients in 1,000 during the five years.
Praluent Performed Nearly as Well:
Cardiologists were enthusiastic about another study published in the New England Journal of Medicine (Nov. 7, 2018). The drug in question, alirocumab (Praluent), is an injectable cholesterol-lowering medication that costs over $6,000 a year. After three years, 3.5 percent of the high-risk heart patients taking Praluent had died. That was statistically better than the 4.1 percent who died while taking placebo. This is a difference of 6 patients in 1,000 over three years.
The news reports about Praluent were far more complimentary than those for either of the omega-3 products, even though the results roughly comparable. Perhaps it is time for health professionals to acknowledge that fish oil supplements may be beneficial after all. If that is too much to swallow, there is evidence that eating at least two servings of fish a week can help prevent fatal heart attacks (JAMA, Oct. 18, 2006).
The Downsides of Fish Oil:
We always like to make sure that people are aware of the potential side effects or unintended consequences of the supplements or medications that they take. A few red flags have gone up for fish oil.
Prostate Cancer:
Epidemiologists suggest men should be cautious about loading up on DHA (American Journal of Epidemiology, online April 24, 2011). They found men getting high levels of DHA had more than double the risk of an aggressive prostate tumor. There was no impact on the more common low-grade prostate cancer. Another study confirmed that men with high levels of omega-3 fats in their bloodstreams are at higher risk of prostate cancer (Journal of the National Cancer Institute, Aug. 7, 2013). However, an analysis covering omega-3 intake and prostate cancer risk of more than 450,000 men did not detect any association (Nutrition and Cancer, March 31, 2015).
Atrial Fibrillation:
For quite a while, doctors thought that people getting more omega-3 fats would be less prone to heart rhythm disturbances such as atrial fibrillation, or Afib. A Canadian study published in the Journal of the American College of Cardiology (Oct. 2014) was a randomized controlled trial of 337 people with atrial fibrillation. This common heart rhythm abnormality can lead to a heart rate as fast as 150 beats a minute.
Volunteers in the trial took either 4 grams of fish oil or placebo daily for as long as 16 months. Sadly, those taking fish oil did not have fewer bouts of atrial fibrillation than those on placebo, nor did they have evidence of lower levels of inflammation.
A new meta-analysis published in the European Heart Journal – Cardiovascular Pharmacotherapy found that people who take omega-3 supplements may increase their risk of atrial fibrillation (April 28, 2021). This heart rhythm abnormality predisposes patients to blood clots that can lead to strokes. The research involved more than 50,000 volunteers with elevated triglycerides and at high risk for heart disease. Those taking omega-3 fats were 29 percent more likely to get a diagnosis of atrial fibrillation.
An earlier review of research on the use of omega-3 fatty acid supplements to prevent or treat atrial fibrillation found inadequate evidence of efficacy (International Journal of Molecular Sciences, Sep. 22. 2015). The question is not settled, however, as another review concluded with “the possibility that these fatty acids could be beneficial in hypertensive patients” (Critical Reviews in Food Science and Nutrition, Jan. 30, 2018).
The People’s Pharmacy Perspective:
We think that reducing fatal heart attacks by 50 percent with fish oil is worthwhile. However, men concerned about prostate cancer and people who have experienced atrial fibrillation might want to stick with eating fish at least two or three meals a week. Even canned tuna or sardines count.
