Fish Oil Supplement Cuts Heart Risks by 43% in Dialysis Patients

A landmark clinical trial has delivered compelling evidence that high-dose fish oil supplementation dramatically reduces serious cardiovascular events in patients undergoing dialysis for end-stage kidney disease. Known as the PISCES (Placebo-Controlled Omega-3 Supplementation in Chronic Kidney Disease and End-Stage Renal Disease) trial, this multinational study was spearheaded by researchers from Monash Health and the School of Clinical Sciences at Monash University in Australia, in collaboration with international partners. The results were presented at the American Society of Nephrology's Kidney Week 2025 and simultaneously published in the prestigious New England Journal of Medicine, marking a potential shift in clinical guidelines for this high-risk population.

The trial enrolled 1,228 adults with a mean age of 64.3 years, all receiving maintenance dialysis therapy at 26 centers across Australia and Canada. Participants had been on dialysis for an average of 3.7 years at enrollment, reflecting a group burdened by advanced chronic kidney disease. Notably, nearly one-third (approximately 32%) had a prior history of major cardiovascular events, underscoring their elevated risk profile. Baseline lipid profiles showed mean low-density lipoprotein (LDL) cholesterol at 1.9 mmol/L and triglycerides at 1.3 mmol/L, with slightly more than half (over 50%) already on statin therapy to manage dyslipidemia.

From 2013 to 2019, researchers randomized 610 patients to receive 4 grams daily of pharmaceutical-grade fish oil capsules rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—the key omega-3 polyunsaturated fatty acids (PUFAs) naturally abundant in fatty fish like salmon and mackerel. The remaining 618 participants received a matching placebo. Patients were followed for a median of 3.7 years, with the primary endpoint being a composite of serious cardiovascular events: myocardial infarction (heart attack), stroke, cardiac death, and vascular-related amputations.

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Striking Results: 43% Risk Reduction

The fish oil group demonstrated a statistically significant 43% relative reduction in the primary endpoint compared to placebo (hazard ratio 0.57; 95% confidence interval 0.45-0.73; p<0.001). this="" translated="" to="" fewer="" heart="" attacks,="" strokes,="" sudden="" cardiac="" deaths,="" and="" amputations—outcomes="" that="" devastate="" dialysis="" patients,="" who="" face="" cardiovascular="" mortality="" rates="" up="" to="" 20="" times="" higher="" than="" the="" general="" population.="" secondary="" analyses="" revealed="" consistent="" benefits="" across="" subgroups,="" including="" those="" on="" statins,="" with="" no="" significant="" increase="" in="" bleeding="" risks="" or="" other="" adverse="">

Adjunct Professor Kevan Polkinghorne, nephrologist at Monash Health and leader of the Australian arm, emphasized the trial's importance: "Dialysis patients endure profoundly high cardiovascular risk, yet few interventions have proven effective. Amid numerous negative trials in this field, these findings stand out." He attributed the robust effect to dialysis patients' notoriously low baseline EPA and DHA levels—often far below those in the general population—making omega-3 repletion particularly impactful.

Expert Insights on Mechanisms and Caveats

Dr. Charmaine Lok, lead author from the University Health Network in Toronto, Canada, described the outcomes as "quite striking" to TCTMD. "Hemodialysis patients exhibit the lowest recorded omega-3 levels in medical literature," she noted. "Elevating these to normal or supranormal ranges likely unleashes cardioprotective effects by addressing atherogenic lipids, chronic inflammation, oxidative stress, and possibly acute thrombosis." While promising, she stressed the need for mechanistic studies to confirm these pathways.

Critically, experts caution against overgeneralization. Professor Polkinghorne specified that benefits apply specifically to hemodialysis patients with kidney failure, not healthy individuals or other groups. Dr. Lok further advised against off-the-shelf supplements: "The PISCES dose was high (4g/day) and ultra-pure. Over-the-counter products may lack potency or purity, potentially yielding inferior results." Patients should consult nephrologists before starting, especially given interactions with anticoagulants or variability in commercial formulations.

This trial reignites hope for simple, accessible therapies in nephrology, potentially influencing future guidelines from bodies like the National Kidney Foundation.

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