New Biomarker Study Clarifies Safety of Fish Oil Use
December 16, 2025, Sioux Falls, SD: A major new analysis published this month in the Journal of the American Heart Association finds that higher circulating blood levels ofomega-3 fatty acids are associated with a significantly lower risk of developing atrial fibrillation (AF) — providing clarity and reassurance amid recent mixed messaging about fish oil supplements and heart rhythm.
The comprehensive biomarker-based study — one of the largest of its kind — analyzed data from hundreds of thousands of participants in the UK Biobank. Researchers showed that individuals with higher omega-3 levels had a lower incidence of AF over a median 12.7 years of follow-up, compared to those with lower omega-3 status.
Importantly, when properly accounting for the confounding effects of age in the statistical models, reported fish oil supplement use was not associated with an increased risk of atrial fibrillation. This result contradicts previous reports from the UK Biobank that mistakenly concluded that fish oil supplements increase the risk for atrial fibrillation.
“These results reinforce that it’s the physiologic status of omega-3 in the blood — not simply supplementation per se — that correlates with AF risk. In pro
perly adjusted models, supplement use showed no increase in AF risk,” said Dr. Bill Harris, President of the Fatty Acid Research Institute (FARI), and senior investigator on the paper.
This biomarker-based approach provides a more nuanced understanding than studies that rely solely on self-reported supplement usage or dose and aligns with a broader body of evidence showing cardiovascular benefits of omega-3 fatty acids.
Key Takeaways from the Study:
- Higher circulating omega-3 fatty acid levels were associated with significantly lower incident AF risk in multivariable models.
- After careful statistical adjustment, fish oil supplement use itself was not linked with a higher AF risk.
- These findings correct the conclusions of previous studies that mistakenly reported (because of an improper statistical analysis) that fish oil supplement use increased risk for atrial fibrillation.
“From a clinical standpoint, these findings help clarify an important misconception,” Dr. Harris explained. “When we look at objectively measured blood omega-3 levels, higher status is associated with lower risk of atrial fibrillation—not higher. This reinforces the importance of evaluating physiology, not assumptions about supplements. Concerns raised by earlier reports linking fish oil use to atrial fibrillation were likely driven by methodological limitations. When age is modeled appropriately, fish oil supplement use does not increase atrial fibrillation risk.”
James O’Keefe, MD, Director of Preventive Cardiology at St. Luke’s Mid-America Heart Institute, Professor of Medicine at University of Missouri, Kansas City, and co- author on this paper, commented: “This very large, methodologically sound and statistically robust study finds that higher omega-3 blood levels correlate with lower risks for atrial fibrillation (AFIB) during long-term follow up. This is in line with other recent studies our group has done, which show that omega-3 in doses typically achieved with consumption of fish/seafood and/or omega-3 over-the-counter supplements reduce risk of AFIB. The only signal for increased AFIB risk comes in people treated with very high-dose omega-3, such as pharmacologic, prescription-strength omega-3 products, used in people at high risk for AFIB. For the vast majority of people, omega-3 intake is a safe and effective nutrient for supporting long-term heart and brain health.”
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About OmegaQuant:
OmegaQuant is an independent, CLIA-certified lab that offers nutritional status testing to researchers, clinicians and the public. OmegaQuant performs analysis in Sioux Falls, SD, for commercial and academic research collaborators, and for consumers interested in monitoring their nutritional status in both blood and breast milk. Its goal is to offer the highest quality fatty acid analytical services to researchers and to provide simple tests of nutritional status to consumers, with the ultimate purpose of advancing the science and use of certain nutrients to improve health. Internationally, OmegaQuant works with the University of Stirling, based in the Scotland, to help process blood samples from Europe. Learn more @ www.omegaquant.com
About FARI:
FARI was established in 2020 as a non-profit foundation that brings together nutrition scientists and biostatistical experts with strong publication records and expertise in fatty acids to accelerate discovery of the relationship between fatty acids, especially omega-3s, and health. FARI is currently the only organization focused directly on discovering and publishing research evaluating the health effects of individual fatty acids. Learn more @ www.faresinst.org