Taking fish oil supplements could raise the risk of heart attack and stroke, a new study suggests.
Among healthy people, regular use of fish oil was found to make them more susceptible to developing heart disease and stroke for the first time, the study found.
Among those who had existing heart disease, however, fish oil consumption was shown to slow the progression of cardiovascular disease and reduce the risk of mortality.
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Researchers analyzed nearly 12 years of data for more than 415,000 participants from the UK Biobank study; the participants ranged in age from 40 to 69.
"Regular use of fish oil supplements might be a risk factor for atrial fibrillation and stroke among the general population, but could be beneficial for progression of cardiovascular disease from atrial fibrillation to major adverse cardiovascular events, and from atrial fibrillation to death," the researchers wrote in the study, which was published in The BMJ (British Medical Journal).
"Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements."
Dr. Jim Liu, a cardiologist at The Ohio State University Wexner Medical Center, who was not involved in the study, pointed out that there has been conflicting data about whether or not fish oil or omega 3 fatty acids can help reduce the risk of cardiovascular disease.
"This study appears to echo the same sentiment that there is still some uncertainty about their relation to heart health," he told Fox News Digital.
"Similar to previous studies, I think this study indicates that fish oil is not necessarily universally good or bad for all."
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Whether or not fish oil is beneficial or harmful depends on an individual's specific underlying health conditions, he said — such as a history of heart attack or atrial fibrillation, and on other factors such as dosing and different formulations of the substance.
"Previous studies have shown that certain formulations of fish oil can help reduce cardiovascular events in people with elevated triglycerides and previous cardiovascular events," Liu noted.
"Overall, this is yet another study that reminds us that there is still a lot that needs to be investigated when it comes to fish oil and heart disease."
Tanya Freirich, a registered dietitian nutritionist in Charlotte, North Carolina, who practices as The Lupus Dietitian, also was not involved in the study but offered insights.
"In this study, there was a slightly increased association between healthy people who took fish oil and developing atrial fibrillation and stroke, whereas for those people who took the fish oil after being diagnosed with cardiovascular disease, there was a slightly decreased association and risk of atrial fibrillation and stroke," she told Fox News Digital.
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"Overall, I would say to take these results with a grain of salt, as it was a prospective study."
A prospective study monitors what people self-report and their eventual health outcomes over time, she noted — versus a control study, where similar people are placed in two groups and one group takes the fish oil while the other does not.
"We don't know about the population of healthy participants and why they decided to take fish oil," Freirich said.
"Perhaps they have a family history of heart disease, or other lifestyle features that are contributing to their risk of developing atrial fibrillation and stroke outside of the fish oil supplement."
As a registered dietitian, Freirich said she recommends most people get their omega 3s from food sources such as salmon, sardines, tuna, ground flaxseed, chia seeds, walnuts and almonds.
"Many people do not get enough omega 3 fatty acids in their diet, and this can be a great way to consume healthy fats while also benefiting from protein and sources of fiber," she said.
When preparing meals, replacing a serving of red meat with fatty fish can promote heart health by decreasing the intake of saturated fats and increasing the intake of omega 3s, according to Freirich.
"Making small changes to your diet over time can have big benefits in reducing your overall cardiovascular risk," she advised.
"Always discuss your supplement use with your medical care providers, as some may be unnecessary or even increase your risk for poor health outcomes."
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Michelle Routhenstein, a New York-based preventive cardiology dietitian at EntirelyNourished.com, agreed that prior research has indicated that taking high doses of fish oil supplements could potentially elevate the risk of atrial fibrillation — while regularly consuming fatty fish four to five times a week may lower that risk.
"We need to recognize that when it comes to fish oil — and many other foods and supplements — more or a concentrated dose isn't necessarily better," Routhenstein, who was not involved in the study, told Fox News Digital.
"It is also important to note that not all fish oil supplements are created equal. Factors like dosage, quality and additional ingredients can influence cardiovascular health outcomes."
To determine the potential benefits of fish oil and the appropriate dosage, Routhenstein recommended consulting with a registered dietitian specializing in heart disease.
Fox News Digital reached out to the study researchers for more detail, as well as several manufacturers of fish oil supplements requesting comment on the findings.
