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  • New research finds that common types of fish oil may not be as beneficial for the heart as they were thought to be.
  • They study found that a high dose of omega-3 fatty acids did not reduce people’s chances of experiencing a major cardiovascular event.
  • About 6 percent of people taking fish oil did have atrial fibrillation or irregular heartbeats.

New research from the Cleveland Clinic has found that common types of fish oil may not be as beneficial for the heart as they were once thought to be.

The study, published in the Journal of the American Medical Associationon November 15, found that a high dose of omega-3 fatty acids did not reduce people’s chances of experiencing a major cardiovascular event.

Evidence regarding the use of fish oil for heart health has been mixed. Oftentimes, the results are influenced by the type of fish oil and the type of placebo used.

Heart doctors suspect different types of fish oils — specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) fatty acids — have different effects on the body.

More research is needed to better understand how the different types impact the cardiovascular system.

“For patients ‘fishing for answers on fish oil,’ the current data supports purified EPA prescription fish oil Vascepa as opposed to over-the-counter fish oil, low dose fish oil, and combination DHA and EPA fish oil. More studies are needed looking at purified EPA fish oil vs. a neutral corn oil placebo, or other formulations of DHA and EPA fish oils vs. purified EPA fish oil,” Dr. Guy Mintz, the director of cardiovascular health & lipidology of cardiology at Northwell Health’s Sandra Atlas Bass Heart Hospital in Manhasset, New York, told Healthline.

In the randomized clinical trial, 13,078 people received either a daily supplementation of high-dose omega-3 fatty acids made of both DHA and EPA or a placebo made of corn oil.

The patients were already taking statins (drugs to lower cholesterol), and they had been previously diagnosed with high cardiovascular risk, hypertriglyceridemia, or low levels of high-density lipoprotein cholesterol.

The study was paused early since there was no significant difference between the two groups.

In addition, about 67 percent of the participants taking the fish oil supplements experienced atrial fibrillation (irregular heartbeat), indicating there may be an increased risk associated with supplements that contain both EPA and DHA fatty acids.

Consequently, the researchers don’t recommend the EPA-DHA omega-3 fatty acid formulation to reduce cardiovascular events.

“Combination DHA and EPA fish oil did not demonstrate any significant cardiovascular benefit, even at high dosages, and specifically in this trial — STRENGTH Trial,” says Mintz.

According to Mintz, fish oil is widely thought to improve heart health because of its anti-inflammatory properties, blood-thinning effects, and improvement in triglyceride levels.

But much of the evidence on fish oil has been mixed.

Past studies have looked at different quantities of fish oil and types of placebos (e.g., corn oil or mineral oil). They also evaluated different fish oil compositions.

These differences make it difficult to compare all the findings, according to Dr. Sanjiv Patel, an interventional cardiologist at MemorialCare Heart & Vascular Institute at Orange Coast Medical Center in Fountain Valley, California.

It’s also likely why the results have varied.

For example, one study, the REDUCE-IT Trial, tested EPA supplements (not including DHA) alongside a mineral oil placebo and found the omega-3 fatty acids had a significant benefit on heart health.

The mineral oil placebo, however, is thought to have had harmful effects — like an increase in LDL cholesterol — on the cardiovascular system.

Some experts suspect this may have caused the fish oil to appear more beneficial than it actually was.

“Mineral oil could in theory cause harm, and if the effect of fish oil were neutral, then a trial comparing the two would lead to the mistaken impression that fish oil was helping prevent bad outcomes,” says Dr. Richard Wright, a cardiologist at Providence Saint John’s Health Center in Santa Monica, California.

Other studies have evaluated DHA or EPA, separately and mixed together, in varying quantities. In some studies, DHA has been linked to an increase in LDL cholesterol, says Mintz.

“There remains the possibility, as stated in the publication, that the root of the discrepancies in the results of these various trials is that a mixed preparation of omega-3 fatty acids (commonly called fish oil) was most commonly utilized, including in the current study,” Wright said.

No studies have convincingly shown that common over-the-counter fish oils lead to clinical benefit, Wright added.

Future studies will need to evaluate the benefits of fish oil that contains purified EPA and no DHA, according to Mintz.

Most heart doctors agree that over-the-counter fish oil products, low-dose fish oil, and combined DHA and EPA supplements provide no benefit.

Some data supports the use of purified prescription fish oil, according to Mintz.

Overall, though, the evidence is unclear.

If you’re considering taking fish oil for your heart health, it’s crucial to first consult a physician.

“Given the slight increase in atrial fibrillation with use of fish oil, one conclusion is clear, patients should always discuss the use of this supplement as well as any other with their doctor,” Patel said.

New research from the Cleveland Clinic has found that fish oil may not be as beneficial for the heart as it was once thought to be. According to the study, high doses of common fish oils did not lower people’s risk of experiencing a cardiovascular event.

Much of the evidence on fish oil has been mixed, and it varies based on the types and quantities of fish oils evaluated along with the type of placebo used. More research is needed to understand how different types of fish oils impact the body.