I’ve been a longtime advocate 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 heart disease. Back then, there was good science behind it, as fish oil was shown to be anti-inflammatory, several studies had shown a lower risk of heart attack, and there didn’t seem to be any downside risk. There were few side effects other than the occasional regurgitation of a fishy taste.
In 2019, the world market for omega-3 fatty acids reached $ 4.1 billion.
There have been several studies in recent years that have questioned the benefits of fish oil supplements. The exception was an attempt called REDUCE-IT, which used a high-purity fish oil called Vascepa (ikosapentethyl). This study looked at people with high triglycerides, high cholesterol, already on a statin to lower their cholesterol, and who had heart disease. It showed a 25 percent reduction in cardiac risk compared to half of the study participants who took a placebo, which was mineral oil. The results were so impressive that Vascepa has become a hugely successful prescription product, with sales of $ 614 million in 2020, 40% more than in 2019.
Another study called STRENGTH looked at a similar group of people and used a slightly different fish oil supplement. It showed no difference between the fish oil and a placebo, which was corn oil.
Nobody could reconcile the different results of these two studies.
Fish oil contains two omega-3 fatty acids called 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.
But the STRENGTH researchers looked at the EPA and DHA blood levels in their participants. If EPA is good for you and DHA is bad, then you would have expected the group with the highest blood levels of EPA, similar to REDUCE-IT levels, 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 did well taking fish oil may only have done well because the placebo group was harmed, which enlarged the difference.
Until a new study is done comparing Vascepa to another, inert placebo, we will not know whether it is effective or whether it has been compared to the wrong placebo.
One of the main reasons I have recommended fish oil to patients for years has been the idea that it won’t do any harm. In a meta-analysis recently published in the European Society of Cardiology (a review and analysis of several studies), the authors found that people treated with high dose (4 grams per day) fish oil for high triglycerides had more atrial fibrillation and irregular heart rhythms . This analysis included all participants in the STRENGTH and REDUCE-IT studies. The conclusion: People who received fish oil were at a significantly higher risk of atrial fibrillation, which can lead to an increased risk of stroke. The Vital Rhythm Study, published in JAMA in March, randomized 12,542 participants to a smaller dose of omega-3 fatty acids (847 mg of mixed DHA / EPA) and 12,577 people to 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 prevention.
Fish oil can no longer be considered harmless. In high doses, it can increase the risk of developing atrial fibrillation.
It was shown to be effective in only one large study, and the results are now controversial. It has only been tested in people with known coronary disease who are already taking a statin and 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 not 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.