Many people take fish oil supplements to protect their hearts either as a prescription or over-the-counter drug. In recent years, however, researchers have questioned not only whether the supplements really improve heart health, but whether they pose a health risk in high doses.
Fish is a well-known source of omega-3 fatty acids – particularly salmon, sardines, and mackerel. Eating fish at least twice a week has been linked to reductions in heart attacks, strokes, and cardiovascular deaths. According to a Harvard studyEating two servings of oily fish a week reduced the risk of death from heart disease by a third.
However, when it comes to consuming fish oil supplements, recent studies show more potential risk than benefit.
Prescription fish oil pills are often prescribed to reduce a person’s triglycerides, a blood fat that, in high concentrations, increases a person’s risk of heart attack and stroke.
Some data has shown that high doses of a fish oil supplement increase the risk of atrial fibrillation, a common heart rhythm disorder, while providing little heart health benefits. A new analysis seems to confirm this increased risk.
The analysis, published in the European Heart Journal – Cardiovascular pharmacotherapy, reviewed five clinical studies of the risk of atrial fibrillation in patients taking fish oil. Overall, cardiac patients who took fish oil doses between 0.84 grams and 4 grams per day had a greater than 33% increased risk of developing atrial fibrillation compared to those who received a placebo.
Atrial fibrillation, or AFib, is an irregular and often rapid heart rate caused by electrical signal problems in the upper chambers of the heart. According to the Mayo Clinic, the condition is not immediately life-threatening, but it can lead to blood clots forming in the heart. These clots can migrate to other parts of the body and block blood flow. Atrial fibrillation can also eventually lead to heart failure.
The increased risk was consistently observed across the studies included in the analysis. However, the heart health benefits were not.
The researchers said there were more cases of AFib in the patients who took the fish oil than in the patients in the placebo group.
Although the risk was not statistically significant in any of the individual studies, the pooled analysis showed that patients taking the supplement were 37% more likely to develop AFib than those taking placebo.
Also of note, only one of the studies showed a reduction in the risk of other heart diseases. That study included a special product called Vascepa, which is icosapentethyl, just one type of omega-3 fatty acid found in fish oil. The risk of cardiovascular events, including heart attack, stroke, and death, due to cardiovascular causes was reduced by 25%.
But even in this study, the AFib risk in the group taking Vascepa increased by 35%.
Another Cleveland Clinic study was shut down last fall because prescription doses not only failed to reduce major cardiac events, but also appeared to increase the risk of atrial fibrillation.
Fish oil supplementation remains controversial as research results are contradicting itself. There have also been some pro-fish oil supplement studies. A 2018 study found that a highly pure form of fish oil had cardiovascular benefits when compared to a mineral oil placebo. However, many cardiovascular health experts questioned the study’s methodology. The fact that mineral oil, which can affect markers of cholesterol and inflammation, was compared may have led to an exaggerated benefit from the fish oil supplement.
Other studies have questioned whether fish oil supplements offer a cardiovascular benefit.
A 2108 study published in JAMA Cardiology looked at 10 studies of fish oil supplements involving 77,917 older adults at high risk for cardiovascular disease and found no significant protection from “major vascular events.” The participants consumed between 226 milligrams to 1,800 milligrams of omega-3 fatty acids daily.
A 2013 and 2018 study published in the New England Journal of Medicine also showed that supplementation did not reduce cardiovascular events or deaths. In this study, it was found that people who do not eat fish may experience some reduction in risk when taking the supplement.