Recent research suggests that while fish oil supplements might provide benefits for individuals with existing cardiovascular disease (CVD), they could potentially increase the risk of heart disease and stroke in healthy individuals. This finding is based on a study involving over 415,000 participants from the UK Biobank, published in the journal BMJ Medicine on May 21, 2024.

Fish Oil Supplements May Increase Risk of Stroke and Heart Issues

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The study included 415,737 participants from the UK Biobank with ages ranging from 40 to 69. Over half (55%) of the participants were women. Participants’ use of fish oil supplements and their dietary intake of oily and non-oily fish were recorded. Health data was tracked until death or the end of the study in March 2021.

About one-third of the participants reported regular use of fish oil supplements. Regular users were predominantly older, white, and female.

Among those without known CVD at the study’s start, regular fish oil supplementation was associated with a 13% increased risk of developing atrial fibrillation. A 5% greater risk of having a stroke.

For participants with existing CVD, regular use of fish oil supplements was linked to a 15% lower risk of progressing from atrial fibrillation to a heart attack. A 9% lower risk of advancing from heart failure to death.

Dr. Michael O. McKinney, a primary physician at Healthy Outlook in Jacksonville, Florida, explained that omega-3 fatty acids in fish oil have anti-inflammatory and lipid-lowering effects.

In individuals with established CVD, these properties can stabilize atherosclerotic plaques, lower serum triglycerides and improve endothelial function, reducing cardiovascular adverse events.

Healthy individuals, high doses of omega-3s might enhance the risk of bleeding due to their anticoagulant effects, potentially outweighing the benefits.

Dr. McKinney also noted that fish oil supplements might cause fatty acid imbalances in healthy people, increasing their heart disease risk.

Dr. Sarah Bonza, founder of Bonza Health in Columbus, Ohio pointed out that some research suggests fish oil might increase the risk of atrial fibrillation in healthy individuals, a condition linked to a higher stroke risk.

For people with preexisting poor cardiovascular health, omega-3s have anti-inflammatory and plaque-stabilizing effects that help slow CVD progression and reduce heart-related death risks.

Experts advise against the use of fish oil supplements for disease prevention in healthy individuals. The American Heart Association does not recommend omega-3 supplements for individuals at low risk for CVD, as the effects are more pronounced in those with the disease. Instead, a heart-healthy diet rich in natural omega-3 sources such as fatty fish is recommended.

Dr. Bonza suggests flaxseed oil or chia seeds as alternatives to fish oil due to their high alpha-linolenic acid (ALA) content, a plant-based omega-3 fatty acid with anti-inflammatory properties.

Other recommended heart-supporting supplements include Coenzyme Q10 (CoQ10) and fiber supplements like psyllium husk. It’s crucial to consult healthcare providers before making any changes to supplement consumption.

This was an observational study which means it does not establish causation. The study did not provide information on the dose or formulation of fish oil supplements used.

Tracy Parker, a senior dietitian at the British Heart Foundation addressed that fish oil supplements should not replace a healthy diet.

The National Institute for Health and Care Excellence (NICE) in the UK does not recommend fish oil supplements for preventing heart and circulatory diseases or stopping another heart attack.

A traditional Mediterranean diet which includes more fish (both white and oily) and less red meat, along with plenty of fruits, vegetables, beans, lentils, nuts, seeds, and whole grains is suggested for heart health.

As a popular source of heart-healthy omega-3 fatty acids, fish oil supplements have long been as a preventive measure against cardiovascular disease.

Approximately 20% of adults over 60 in the United States regularly consume these supplements to support heart health.

A new study published in BMJ Medicine reveals that regular use of fish oil supplements might actually increase the risk of first-time stroke and atrial fibrillation (AFib) among people in good cardiovascular health.

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Atrial fibrillation is a type of arrhythmia characterized by an irregular heartbeat often described as a fluttering or pounding sensation in the chest.

Dr. Andrew Freeman, director of cardiovascular prevention and wellness at National Jewish Health in Denver, noted that over-the-counter fish oil is rarely recommended and is not included in guidelines from professional medical societies.

The study analyzed data from over 415,000 people aged 40 to 69 who participated in the UK Biobank, a health study in the United Kingdom.

About one-third of these participants followed for an average of 12 years, reported regular use of fish oil supplements.

The findings show that for individuals without heart issues, regular use of fish oil supplements was associated with a 13% higher risk of developing atrial fibrillation and a 5% increased risk of stroke.

Over-the-counter fish oil supplements often suffer from a lack of purity and consistency and may contain contaminants and heavy metals such as mercury.

Freeman highlighted that studies over the past decade have generally not shown positive outcomes for over-the-counter fish oil with some research indicating potential harm such as an increased risk of stroke and AFib.

The study found that people with existing heart disease at the beginning of the research had a 15% lower risk of progressing from atrial fibrillation to a heart attack and a 9% lower risk of progressing from heart failure to death when they regularly used fish oil.

Prescription versions of fish oil such as Vascepa and Lovaza are used to address high triglycerides in people with cardiovascular disease risk but even these prescription-strength, highly purified versions of fish oil have shown risks for AFib and sometimes stroke.

Dr. Richard Isaacson, an Alzheimer’s preventive neurologist and director of research at the Institute for Neurodegenerative Diseases in Boca Raton, Florida, addressed the importance of individualized approaches to omega-3 fatty acid intake.

He recommends testing omega-3 fatty acid levels before supplementation, as finger-prick tests are readily available and accurate.

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Isaacson advises getting omega-3s from food sources whenever possible citing sardines and wild-caught salmon as excellent options due to their high omega-3 content and lower mercury levels. He cautions against farm-raised salmon due to impurities in the water where they are raised.

Other good sources of omega-3 fatty acids include lake trout, mackerel, herring, and albacore tuna. Due to mercury levels, consumption of albacore tuna should be limited to twice a week.

Non-fish sources of omega-3s, such as algae, seaweed, chia seeds, edamame, flaxseed, hempseeds, and walnuts are also beneficial, although they contain a different form of omega-3 that may be harder to metabolize in individuals with higher levels of omega-6 fatty acids.

Prescription omega-3 fatty acids are superior to over-the-counter options due to their purity and quality, but they can be expensive.

For those opting for over-the-counter omega-3s, Isaacson recommends buying from reputable companies directly from their specific websites to ensure freshness and quality.

The US Food and Drug Administration (FDA) does not monitor the supplement industry to ensure that products contain what they claim or that they are free from contaminants.

Consumers should look for third-party testing labels from organizations such as US Pharmacopeia (USP),, and NSF International.

The largest randomized control trial of fish oil in a population without known heart problems conducted in 2018, showed a 28% lower risk of heart attacks and a 17% reduced risk of all heart disease events among participants taking fish oil supplements.

These supplements were not associated with a lower risk of stroke. Dr. JoAnn Manson, co-leader of the trial, stated that the study used quality-controlled sources of supplements and carefully monitored dosages.

Manson noted that doses of 1g per day and lower are not associated with a meaningful increase in atrial fibrillation, but higher doses show nearly 50% increased risk.

The omega-3 fatty acids in fish oil can affect the electrical rhythms of the heart, particularly the beating of the atrial chambers, contributing to this risk.

The American Heart Association does not recommend fish oil supplements for preventing heart disease due to the potential increased risk of atrial fibrillation.

Experts advise following a healthy diet including consuming fish one to two times a week, exercising regularly, minimizing stress, and getting enough sleep to protect heart health.

For individuals with a higher likelihood of heart problems, the anti-inflammatory, anti-clotting, and triglyceride-lowering benefits of omega-3 fats may outweigh the risks for those who do not consume fish regularly.

Dr. Alice Lichtenstein, director and senior scientist at the Cardiovascular Nutrition Laboratory at Tufts University addressed that while the study’s observational nature means it cannot prove causation, the results align with existing knowledge about the dose-dependent risks of fish oil supplementation.

For people without a history of heart problems, regular fish oil supplementation appears to increase the risk of atrial fibrillation and stroke.

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