Many people take one every morning for the heart, the joints, or just as a kind of health insurance.
Few would guess the same active ingredient has just shown up in a cancer trial.
A phase 3 trial from the University of Leeds tested four grams a day of pure EPA, a key omega-3 fat in fish oil. It lifted 5-year survival to 62 percent after liver surgery for bowel cancer that had spread, compared with 45 percent on placebo.
The trial design was published in BMJ Open in 2023.
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Results were presented in October 2026 at the ESMO Congress in Madrid.
The trial randomized 418 patients at 13 UK hepatobiliary surgery centers to high-purity prescription icosapent ethyl, sold as Vascepa in the US and Vazkepa in Europe, or a mineral oil placebo.
Patients started the capsules at least a day before surgery and continued for up to four years afterward. Over the follow-up, the risk of death was about 32 percent lower on EPA than on placebo.
The headline came from a secondary endpoint
The trial's main question was not about survival. It was about whether EPA could delay cancer recurrence after surgery. On that front, the answer was no.
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Progression-free survival, meaning time without new cancer activity, was 13.5 months on EPA versus 12.9 months on placebo. The difference was not statistically significant.
Overall survival at five years was a prespecified secondary endpoint. There, the gap between the two groups was clear and reached statistical significance.
The trial also found no excess bleeding, no excess heart rhythm problems, and no hit to patients' quality of life.
Lead investigator Mark Hull from the University of Leeds spoke about the result in the trial announcement.
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He said it "is clinically meaningful for the group of patients who have had surgery for bowel cancer spread to the liver and in whom the cancer frequently comes back", accoridng to News-Medical.
He added that the same pattern, longer overall survival without a clear progression-free survival benefit, has shown up in cancer immunotherapy trials.
More research is needed to work out whether EPA acts on the body's immune response to cancer, he said.
This is not a reason to swap your fish oil capsule
The four-gram dose used in the trial was high-purity prescription icosapent ethyl, which is nearly pure EPA. That is a different product from the fish oil capsule in the pharmacy aisle.
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A standard fish oil capsule contains far less EPA than the trial dose and includes DHA alongside it. Reaching four grams of pure EPA from ordinary over-the-counter supplements is not practical.
The drug is already approved by the US Food and Drug Administration for lowering cardiovascular risk in people with high triglycerides, based on the earlier REDUCE-IT trial. It has no cancer indication.
The trial tested EPA in a specific setting. The capsules were taken by adults undergoing curative-intent surgery for bowel cancer that had spread to the liver, starting before the operation and continuing for years after.
The finding does not translate into guidance for other cancers or for healthy readers wondering about a preventive dose.
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The investigators said the survival result needs to be confirmed in further studies before high-dose EPA can enter routine care for this patient group. The drug remains a prescription for cardiovascular risk only.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.