I’ve been a long-time supporter of fish oil supplements for heart disease prevention. I did a radio show every Sunday night for several years talking about the importance of lifestyle changes combined with high-dose omega-3s for preventing coronary problems. There was good science behind this at the time, as fish oil had been shown to be anti-inflammatory, several studies had shown a lower risk of heart attacks, and there didn’t seem to be any downside risk. There were few side effects other than the occasional regurgitation of fishy taste.
In 2019, the global omega-3 fatty acid market reached $ 4.1 billion.
In the past few years there have been several studies questioning the benefits of fish oil supplements. The exception was an attempt called REDUCE-IT, which used a high-purity fish oil called Vascepa (icosapent ethyl). This study looked at people with high triglycerides and high cholesterol who were already on a statin to lower their cholesterol and who had heart disease. It showed a 25% decrease in heart risk compared to half of the study participants who took a placebo, which was mineral oil. The results were so impressive that Vascepa became a hugely successful prescription product with sales of $ 614 million in 2020, up 40% from 2019.
Another experiment called STRENGTH looked at a similar group of people and used a slightly different fish oil preparation. There was no difference between the fish oil and a placebo that was corn oil.
Nobody could reconcile the different results of these two studies.
Fish oil contains two omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
In a study published this month at the American College of Cardiology (ACC) meeting and simultaneously published in JAMA Cardiology, the authors found that while Vascepa is pure EPA, the STRENGTH oil is a mixture of DHA and EPA is.
However, the STRENGTH investigators looked at the EPA and DHA blood levels in their participants. If EPA is good for you and DHA is bad, one would have expected the group with the highest blood levels of EPA, similar to what was found in REDUCE-IT, to do better. They have not.
Another reason has been suggested. It is possible that the placebo in REDUCE-IT was not a placebo at all. It was mineral oil that can be flammable. In other words, the group that took fish oil well may only have done well because the placebo group was harmed, which enlarged the difference.
Until a new study is completed comparing Vascepa with another, inert placebo, we will not know whether it is effective or whether it was compared to the wrong placebo.
One of the main reasons I have recommended fish oil to patients for years was the idea that it didn’t do any harm. In a meta-analysis (review and analysis of several studies) recently published in the European Society of Cardiology, the authors found that people treated with high-dose fish oil (4 grams per day) for high triglycerides had more atrial fibrillation and irregular heart rhythm. This analysis included all participants in the STRENGTH and REDUCE-IT studies. The conclusion: people who received fish oil had a significantly higher risk of atrial fibrillation, which can lead to a higher risk of stroke. The Vital Rhythm Study, published in JAMA in March, randomized 12,542 participants who received a lower dose of omega-3 fatty acids (847 mg of mixed DHA / EPA) and 12,577 people who received a placebo with olive oil. This study did not show a significant incidence of atrial fibrillation, suggesting that lower doses are safer but may not help prevent it.
Fish oil can no longer be considered harmless. In high doses, it can increase the risk of atrial fibrillation.
It has been shown to be effective in just one large trial, and its results are now controversial. It has only been tested in people with known coronary disease who are already taking a statin, at high doses of 4 grams per day. Other groups of people either do not benefit or have never been tested.
Based on these new studies, I will no longer recommend fish oil to my patients in the future to prevent heart problems. Following science can lead to unexpected places.
Noteworthy: Every study so far confirms the importance of diet, exercise, and weight loss in preventing heart problems, albeit without the use of fish oil supplements.
David Becker is a certified cardiologist with Chestnut Hill Temple Cardiology in Flourtown. He has been in the practice for more than 30 years.