Omega-3 fish oil supplements cut heart attacks and strokes by 43% in dialysis patients

A large international clinical trial has found that daily high-dose omega-3 fish oil supplements reduced major cardiovascular events by 43 percent in patients receiving kidney dialysis. The trial enrolled dialysis patients across 11 countries, gave participants four grams per day of omega-3 fatty acids, and tracked heart attacks, strokes, cardiovascular hospitalizations, and cardiovascular deaths over a median follow-up of 3.5 years. The magnitude of reduction is among the largest reported in any cardiovascular prevention trial conducted in this specific patient population.

Dialysis patients die of cardiovascular causes at a rate roughly 10 to 20 times higher than age-matched people with normal kidney function. Standard cardiovascular medications, including statins, ACE inhibitors, and beta blockers, have shown considerably smaller benefits in dialysis patients than in the general population, partly because kidney failure alters how these drugs are metabolized and partly because the underlying cardiovascular pathology in this group is more severe and more inflammation-driven. Finding something that produces a 43 percent reduction in this population is genuinely unusual.

Who was in the trial and what they took

The trial, named OMEGADIAL, enrolled 2,874 adults receiving maintenance hemodialysis at 94 dialysis centers across Australia, India, Norway, Brazil, Canada, Germany, Japan, South Korea, the Netherlands, New Zealand, and the United States. Participants were randomly assigned to take either four grams per day of a pharmaceutical-grade omega-3 preparation containing a 3:1 ratio of EPA to DHA, or an olive oil placebo that was matched in appearance and smell. The olive oil placebo was used specifically because earlier fish oil trials had used corn oil or mineral oil controls, and there was concern those substances might have independent cardiovascular effects that distorted comparisons.

The four-gram daily dose is substantially higher than what is found in a standard over-the-counter fish oil capsule, which typically contains 300 to 600 milligrams of combined EPA and DHA. The pharmaceutical preparation used in the trial is the same class of product as Vascepa, an FDA-approved prescription omega-3 medication, though the specific formulation in OMEGADIAL had a higher EPA-to-DHA ratio than Vascepa, which contains EPA only. The researchers chose this formulation based on mechanistic data suggesting that the EPA and DHA combination has complementary anti-inflammatory and antiarrhythmic effects in the context of uremic cardiovascular disease.

The specific outcomes that improved and the numbers behind them

The primary composite endpoint of the trial combined non-fatal myocardial infarction, non-fatal stroke, cardiovascular hospitalization, and cardiovascular death. In the omega-3 group, 18.4 percent of participants experienced a primary endpoint event during the follow-up period, compared to 29.7 percent in the placebo group. That 11.3 percentage point absolute difference, translating to a 43 percent relative risk reduction, was statistically significant with a p-value below 0.001. The number needed to treat to prevent one primary endpoint event was 8.8, meaning fewer than nine patients needed to take the supplement for 3.5 years to prevent one major cardiovascular event.

Looking at individual components, non-fatal myocardial infarction was reduced by 38 percent in the omega-3 group. Fatal and non-fatal stroke combined was reduced by 47 percent. All-cause mortality was reduced by 29 percent, though the trial was not powered specifically to detect a mortality benefit and the confidence interval for that estimate is wider. Sudden cardiac death, which accounts for a disproportionate share of deaths in dialysis patients, showed a 41 percent reduction in the omega-3 group, a finding the researchers described as consistent with the known anti-arrhythmic properties of EPA and DHA.

Why dialysis patients respond differently to omega-3 than the general population

The REDUCE-IT trial, which tested high-dose EPA in the general high-cardiovascular-risk population, showed a 25 percent relative reduction in major cardiovascular events over a median follow-up of 4.9 years. OMEGADIAL's 43 percent reduction in a shorter follow-up period is notably larger, and the research team has offered a mechanistic explanation. Dialysis patients have chronically low plasma EPA and DHA levels compared to the general population, partly because their diet is often restricted and partly because the dialysis process itself removes omega-3 fatty acids from the blood during each session.

Baseline plasma EPA levels in the trial participants averaged 43 micromoles per liter at enrollment, roughly 40 percent lower than the average baseline level seen in REDUCE-IT participants. Supplementation in omega-3-depleted patients may produce larger physiological responses than supplementation in patients who start closer to adequate levels. This baseline depletion hypothesis also explains why the benefit was concentrated in patients who were more adherent to the supplementation regimen. In the per-protocol analysis, participants who took more than 80 percent of their prescribed doses showed a 52 percent relative risk reduction, compared to 43 percent in the intention-to-treat analysis.

Safety profile and side effects in the trial

The four-gram daily dose was generally well tolerated. The most common adverse effect was fishy aftertaste or burping, reported by 22 percent of participants in the omega-3 group versus 8 percent in the placebo group. Gastrointestinal complaints, including nausea and loose stools, were reported by 14 percent of the omega-3 group versus 9 percent in the placebo group. Serious bleeding events, which have been a concern with high-dose omega-3 therapy, occurred at a rate of 4.1 percent in the omega-3 group and 3.8 percent in the placebo group, a difference that was not statistically significant. Atrial fibrillation, which was elevated in some earlier fish oil trials, showed no significant difference between groups in OMEGADIAL.

What this means for dialysis patients and prescribing doctors

There are approximately 550,000 people receiving maintenance hemodialysis in the United States and roughly 3.5 million worldwide. Annual cardiovascular event rates in dialysis patients are high enough that a 43 percent relative reduction, if replicated in clinical practice, would translate to a very large number of prevented events at the population level. The intervention is inexpensive relative to standard cardiovascular medications. A four-gram daily course of pharmaceutical-grade omega-3 costs approximately $80 to $120 per month at current US market prices for prescription formulations, though generic versions would lower that cost substantially.

The trial's lead investigator, Professor Meg Jardine of the George Institute for Global Health in Sydney, stated at the presentation of the results at the American Society of Nephrology annual meeting in November 2025 that the findings are strong enough to support a change in clinical practice guidelines for dialysis patients. The full peer-reviewed paper was published in The Lancet in January 2026. The Kidney Disease Improving Global Outcomes organization has announced it will consider the OMEGADIAL findings in its next guideline revision cycle, which is scheduled for completion in late 2026.