The finding comes from the PISCES trial, involving 1,228 hemodialysis patients and published in the New England Journal of Medicine. Participants who took four grams of fish oil daily had 43% fewer serious cardiovascular events than those on placebo.
The composite endpoint counted heart attacks, strokes, cardiac deaths and amputations caused by blocked blood vessels. That translates to a hazard ratio of 0.57 (95% confidence interval 0.47 to 0.70, p less than 0.001), one of the largest effects yet documented in this group.
Why dialysis patients are so vulnerable
People on dialysis have blood levels of EPA and DHA, the two long-chain omega-3 fats found in oily fish, that sit well below the general population. That deficit sits on top of chronic inflammation and rapid hardening of the arteries.
"Patients on dialysis have extremely high cardiovascular risk, and very few therapies have been shown to reduce that risk," said Adjunct Professor Kevan Polkinghorne, who led the Australian arm of the trial at Monash Health. "In a field where many trials have been negative, this is a significant finding."
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Polkinghorne also tied the size of the benefit to the depleted starting point. Dialysis patients typically have much lower levels of EPA and DHA than the general population, he said, and that may help explain the magnitude of the benefit.
What the trial actually tested
Researchers randomly assigned 1,228 adults on maintenance hemodialysis at 26 sites in Australia and Canada to either 4 grams a day of omega-3 fatty acids (1.6 grams EPA and 0.8 grams DHA) or a corn oil placebo, according to the trial data. Follow-up ran up to 3.5 years.
Serious bleeding, a well-known concern with high-dose omega-3s, was actually less common in the fish oil group (4.8% versus 7.6% on placebo). Other serious adverse events were similar between groups. The results were first presented at the American Society of Nephrology Kidney Week in 2025.
What this does not mean for everyone else
The finding applies to a specific group: adults on hemodialysis for kidney failure. Polkinghorne stressed that the results apply specifically to people undergoing hemodialysis, and he cautioned against generalizing to healthy people or other patient groups.
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Recent evidence in the general population has been much less encouraging. Reviews of fish oil supplements in healthy adults have delivered mixed results for blood pressure, memory and general heart protection.
Kidney failure is far from rare in the United States. National ESRD Network data put 516,837 people on dialysis as of March 31, 2025, most of them on in-center hemodialysis. Cardiovascular disease is the leading cause of death in this population, and standard dialysis screening tools can still miss the risk.
Anyone on dialysis who is thinking about adding fish oil should raise it with their nephrologist first. Dose, purity and interactions with blood thinners are decisions for the treating team, not the supplement aisle.
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This article is made and published by Mie Hermansen, who may have used AI in the preparation.