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A major new randomized clinical trial has found that daily fish oil supplementation significantly reduces the risk of serious cardiovascular events in patients undergoing hemodialysis, a group at exceedingly high risk for heart disease and related complications. The study results, presented at Kidney Week 2025 and published simultaneously in the New England Journal of Medicine, offer cautious optimism for this vulnerable population, where many conventional cardiovascular medications have failed to demonstrate benefit.
Hemodialysis patients face cardiovascular mortality rates more than 20 times higher than the general population, yet treatment options to mitigate this risk have been limited. The international PISCES trial examined 1228 adults on maintenance hemodialysis across Canada and Australia over 3.5 years. Participants were randomized to receive either 4 grams daily of fish oil containing the omega-3 fatty acids EPA (1.6 g) and DHA (0.8 g), or a corn oil placebo.
The results were striking. The fish oil group experienced a 43% lower risk of the composite primary endpoint encompassing all serious cardiovascular events—including sudden and nonsudden cardiac death, fatal and nonfatal myocardial infarction, peripheral vascular disease leading to amputation, and fatal or nonfatal stroke—compared to placebo (HR 0.57; 95% CI, 0.47-0.70; p<0.001). This translated to 158 events in the fish oil group versus 309 in placebo, or 0.31 versus 0.61 per 1000 patient-days.
Remarkably, benefits were consistent regardless of prior cardiovascular events. Patients with previous cardiac events who took fish oil had a risk similar to placebo patients without prior events, suggesting fish oil may substantially “reset” elevated cardiovascular risk in this population. Secondary endpoints also favored fish oil, with reduced rates of cardiac death (HR 0.55), myocardial infarction (HR 0.56), peripheral vascular disease requiring amputation (HR 0.57), and stroke (HR 0.37). No increase in serious bleeding or other adverse events was observed.
Dr. Charmaine E. Lok, lead author and Senior Scientist at the University Health Network and University of Toronto, highlighted that “fish oil supplementation is a simple, well-tolerated intervention that could have a meaningful impact” for dialysis patients, noting that omega-3 fatty acids possess antithrombotic, anti-inflammatory, and antiarrhythmic properties. These findings provide rare evidence of cardiovascular risk reduction where therapies such as statins and ACE inhibitors have previously failed in this group.
Nephrology expert Dr. David Charytan of NYU Grossman School of Medicine called this a “major achievement,” underscoring that it is “the first large outcome study to show cardiovascular risk reduction in dialysis patients.” However, he cautioned that more large, well-powered studies are needed for confirmation, noting the 24% dropout rate and the fish oil formulation not being FDA-approved in the US. He also pointed to less striking effects on all-cause mortality, indicating ongoing inquiry into mechanisms and outcomes is warranted.
Contextually, the 43% risk reduction surpasses those seen in landmark cardiovascular studies such as the CREDENCE trial for SGLT2 inhibitor canagliflozin (30%) and FLOW trial for semaglutide (24%), affirming the potential clinical significance of these findings.
Implications for Public Health and Daily Decisions
For health-conscious consumers and healthcare professionals, the PISCES trial signals a potential breakthrough in reducing cardiovascular risk among hemodialysis patients—a group with urgently unmet needs. The simplicity and tolerability of daily fish oil supplementation could enable widespread adoption once further validation is complete.
However, patients should not self-prescribe omega-3 supplements without consulting their healthcare providers. The specific formulation and dosage used in the study are key parameters, and safety monitoring remains important.
Limitations and Balanced Perspective
Despite robust results, the trial’s authors and commentators acknowledge limitations including the dropout rate and the need for replication in diverse populations. Observed benefits in cardiovascular endpoints may not fully translate to mortality reduction, prompting calls for continued research to elucidate long-term outcomes and mechanisms.
Additionally, fish oil is not a panacea. It complements but does not replace comprehensive cardiovascular care, including lifestyle modifications and management of comorbid conditions.
Overall, the PISCES trial represents a significant advance in cardiovascular care for dialysis patients, meriting further study with cautious optimism.
Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.
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