Fish oil has been considered healthy for the heart for decades. Many people choose over-the-counter supplements to reduce their risk of heart disease. Still, research has produced inconsistent results as to whether there are any real health benefits.
Most studies have shown that the heart benefits associated with fish oil supplements are minor and may not be worth the potential risks involved. However, new evidence suggests that high doses of prescription fish oil can actually damage the heart.
A clinical trial led by the Cleveland Clinic was stopped prematurely because prescription doses not only did not reduce major cardiac events, but also appeared to increase the risk of atrial fibrillation, an irregular heartbeat that can lead to blood clots, stroke, or heart failure.
The study, known as the STRENGTH study, included 13,078 patients who received either daily high-dose omega-3 fatty acids or corn oil placebos.
The results contrast sharply with the more promising results of a 2018 study that found that a highly purified form of fish oil had cardiovascular benefits when compared to a mineral oil placebo.
However, many cardiovascular health experts consider the earlier study to be controversial. The mineral oil had a negative impact on cholesterol and inflammation markers, which may have exaggerated the benefits of the fish oil supplement.
“Compared to mineral oil used in the previous study, corn oil did not increase either cholesterol or inflammation markers, suggesting it is a truly neutral placebo,” said senior author Dr. Steven Nissen, senior academic staff at the Cardiovascular and Thoracic Institute at the Cleveland Clinic, said in a statement.
The STRENGTH study was conducted in 675 hospitals worldwide. Researchers wanted to monitor the effects of fish oil supplements on cardiovascular death, non-fatal heart attack, non-fatal stroke, coronary artery revascularization, and hospitalization for unstable angina.
The study was stopped after 1,384 patients achieved a primary result. At the end of the study, 785 patients in the intervention group and 795 in the placebo group had a major cardiovascular event.
The study showed a 67% increase in atrial fibrillation in the participants who received the fish oil supplements.
“Given that two large clinical studies have now shown a higher incidence of atrial fibrillation with high doses of omega-3 fatty acids, this observation warrants further investigation.” said Dr. Michael Lincoff, vice chairman of the cardiovascular medicine department at the Cleveland Clinic.
The study results also show that a review of all fish oil products should be considered, including over-the-counter supplements, he added. They follow a UK study published last spring that found that fish oil supplements slightly increased the risk of prostate cancer.
Health experts emphasize that it is It is important to weigh all of the potential benefits and risks when considering dietary supplements. They advise people to consult their doctor before adding or stopping any supplements.