Fish Oil Reduces Heart Risk in Dialysis Patients: PISCES Trial Results

A daily fish oil supplement containing the omega-3 fatty acids EPA and DHA may significantly reduce the risk of serious cardiovascular events for individuals undergoing hemodialysis for kidney failure. A large international clinical trial, the PISCES trial, revealed a 43 percent lower rate of events – including heart attack, stroke, cardiac death, and vascular-related amputations – among those taking a four-gram daily dose compared to a placebo group. The findings, presented at the American Society of Nephrology Kidney Week 2025 and published in The New England Journal of Medicine, offer a potentially important new avenue for managing cardiovascular risk in a population facing exceptionally high rates of heart disease.

Dialysis Patients and Cardiovascular Risk: A Unique Challenge

Kidney failure necessitates dialysis, a life-sustaining treatment that filters waste products from the blood. However, dialysis itself places a substantial burden on the cardiovascular system. Patients on dialysis experience dramatically elevated rates of heart attack, stroke, and other serious cardiac complications compared to the general population. This heightened risk is linked to a complex interplay of factors, including inflammation, oxidative stress, and imbalances in electrolytes and hormones. Currently, effective therapies to mitigate this risk have been limited, making the PISCES trial results particularly noteworthy.

Adjunct Professor Kevan Polkinghorne, a nephrologist at Monash Health in Australia and a lead investigator in the trial, emphasized the significance of the findings. “Patients on dialysis have extremely high cardiovascular risk, and incredibly few therapies have been shown to reduce that risk,” he said. “In a field where many trials have been negative, this is a significant finding.”

The PISCES Trial: Design and Key Findings

The PISCES trial was a randomized, placebo-controlled clinical trial involving 1,228 participants receiving dialysis at 26 sites across Australia and Canada. Participants were randomly assigned to receive either four grams of fish oil daily or a placebo. The primary endpoint of the study was the occurrence of a composite cardiovascular event, encompassing heart attack, stroke, cardiac death, and vascular-related amputations. The trial’s design, as detailed in ScienceDaily’s coverage, aimed to provide robust evidence regarding the potential benefits of omega-3 supplementation in this high-risk population.

The 43 percent reduction in major cardiovascular events observed in the fish oil group is a substantial effect. However, it’s crucial to understand that this is a relative risk reduction. The absolute risk reduction – the difference in the actual number of events occurring in each group – would provide a more nuanced understanding of the clinical benefit. Further analysis of the trial data is needed to determine the absolute risk reduction and to identify which patients are most likely to benefit from fish oil supplementation.

Why Fish Oil? Understanding EPA and DHA

Omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential nutrients with well-established roles in cardiovascular health. They are naturally found in fatty fish like salmon, tuna, and mackerel. These fatty acids possess anti-inflammatory properties, can help lower triglyceride levels, and may improve blood vessel function. Monash University’s reporting highlights that dialysis patients often have lower levels of EPA and DHA compared to the general population, potentially contributing to their increased cardiovascular risk.

Limitations and Generalizability

Professor Polkinghorne cautioned that the findings apply specifically to patients undergoing hemodialysis. Hemodialysis is the most common type of dialysis, but other forms, such as peritoneal dialysis, exist. It remains unclear whether the benefits of fish oil supplementation would extend to patients on other types of dialysis or to those with earlier stages of kidney disease. The study population was limited to individuals in Australia and Canada, raising questions about the generalizability of the results to other populations with different genetic backgrounds, dietary habits, and healthcare systems.

The trial also did not investigate the optimal dose of fish oil. While four grams per day was effective in this study, it’s unknown whether lower or higher doses would provide similar benefits. The long-term effects of fish oil supplementation in dialysis patients remain to be determined.

What Comes Next: Refining Guidance and Further Research

The PISCES trial results are likely to prompt a re-evaluation of current guidelines for cardiovascular risk management in dialysis patients. While the findings do not constitute a formal recommendation for universal fish oil supplementation, they provide compelling evidence to support its consideration as part of a comprehensive treatment plan. Clinicians will need to weigh the potential benefits against the potential risks – such as bleeding – and individualize treatment decisions based on each patient’s specific circumstances.

Further research is needed to address the remaining uncertainties. Future studies should investigate the effects of fish oil supplementation on different types of dialysis, explore the optimal dose and duration of treatment, and identify biomarkers that can predict which patients are most likely to respond. SciTechDaily’s report suggests ongoing analysis of the PISCES trial data will provide further insights into these questions.

For individuals currently undergoing hemodialysis, discussing the potential benefits and risks of fish oil supplementation with a qualified nephrologist is crucial. This conversation should be part of a broader discussion about managing cardiovascular health and optimizing overall well-being.