Supplement

Omega-3 (EPA/DHA)

Fatty acid · fish oil / algae oil

14 min read 20 sources, checked November 13, 2026

In the BK-Score: Well supported – human evidence 8 out of 10, safety data 9 out of 10. The data in humans are solid.

Omega-3 fatty acids (EPA and DHA) are among the most thoroughly studied dietary supplements of all. Three large randomized trials missed their primary endpoint, and in 2019 the EMA removed the indication for secondary prevention after a heart attack.

What omega-3 is

EPA and DHA are long-chain polyunsaturated fatty acids from fatty fish and algae oil. EPA tends to have an anti-inflammatory effect, while DHA is a building block of the brain and nerve tissue. Lowering triglycerides is the most clearly established effect.

The omega-3 index in the blood serves as a status marker. The quality of the oils matters, because low-quality products can oxidize; the TOTOX value is commonly stated.

Why the evidence is considered mixed

Large randomized trials with hard endpoints exist - but their results partly contradict each other: VITAL, STRENGTH and ASCEND were negative, REDUCE-IT with highly purified EPA and PISCES in dialysis patients were positive. Much more is claimed in marketing than the studies support.

The key is to distinguish between the prespecified primary endpoint and the many secondary analyses. If the primary endpoint is missed, individual positive secondary findings are indications, not proof.

It all began with an observation. From 1970 onwards, the Danish physicians Hans Olaf Bang and Jørn Dyerberg found a lot of EPA in the blood of Greenlanders in Uummannaq and, especially in the men, lower blood lipids than in Danes of the same age. The fat in their diet came essentially from marine mammals such as seal and whale, not primarily from fish. The often-told low heart attack rate was never studied by the two themselves; it was based on annual reports of Greenland's chief medical officer, although many settlements at the time had no physician on site. A review of the later studies (Fodor 2014) found coronary heart disease in Inuit in Greenland, Canada and Alaska about as often as in other populations.

What is well supported

Hardly any dietary supplement has been tested as thoroughly. There are three large placebo-controlled trials with hard endpoints alone: VITAL with 25,871 participants over a median of 5.3 years, ASCEND with 15,480 people with diabetes over 7.4 years and STRENGTH with 13,078 high-risk patients at 675 centers in 22 countries.
The heart attack finding in VITAL was significant. As a secondary result, total heart attacks came in at HR 0.72 (95% CI 0.59-0.90); the confidence interval does not include 1. Because the primary endpoint was missed, this is an indication, not proof - but it is a result that deserves to be mentioned.
Two large trials with hard endpoints were positive. REDUCE-IT reduced major cardiovascular events by 25 percent (HR 0.75) with highly purified EPA in statin-treated high-risk patients. PISCES found 43 percent fewer major cardiovascular events (HR 0.57) with fish oil in 1,228 hemodialysis patients, a group in which almost all cardiovascular trials had previously been neutral. Both results apply to their specific patient group; the limitations are listed further below.
Still approved as a medicine for lowering triglycerides. On 2019-03-29 the EMA removed the indication for secondary prevention after a heart attack; the approval for lowering triglycerides explicitly remained in place.
The safety data are exceptionally broad. The meta-analysis by Abuknesha 2026 covers 35 randomized trials with 114,592 participants aged 50 and over, each lasting at least twelve months and using at least 500 mg of EPA plus DHA daily. An increased risk of atrial fibrillation was found only in people at high cardiovascular risk combined with more than 1,500 mg daily; in the other groups, the odds ratios were 1.07, 1.06 and 1.03. The analysis was commissioned by the manufacturers' association GOED; an earlier meta-analysis reaches a different result for common amounts (see below).

What the studies show

VITAL: primary endpoint missed

Manson 2019 randomized 25,871 people (men aged 50 and over, women aged 55 and over) from the US general population, without preselection for risk, to 1 g of marine n-3 daily or placebo; median follow-up 5.3 years. Major cardiovascular events occurred 386 versus 419 times, HR 0.92 (95% CI 0.80-1.06; p=0.24) - not significant. Invasive cancers: 820 versus 797, HR 1.03 (0.93-1.13; p=0.56). As secondary results, total heart attacks came in at HR 0.72 (0.59-0.90), stroke at HR 1.04 (0.83-1.31), cardiovascular death at HR 0.96 (0.76-1.21).

STRENGTH: stopped early

Nicholls 2020 studied 13,078 statin-treated high-risk patients with elevated triglycerides and low HDL cholesterol (mean age 62.5 years, 70 percent with diabetes) at 675 centers in 22 countries, with 4 g of omega-3 carboxylic acid daily against corn oil. The trial was stopped at 1,384 of a planned 1,600 events because a benefit had become unlikely. The primary endpoint occurred in 785 (12.0 percent) versus 795 (12.2 percent), HR 0.99 (0.90-1.09; p=0.84).

ASCEND: no effect in people with diabetes

ASCEND studied 15,480 people with diabetes and no known cardiovascular disease, with 1 g of n-3 daily against olive oil over 7.4 years, at an adherence of 76 percent. Serious vascular events occurred in 689 people (8.9 percent) versus 712 (9.2 percent), rate ratio 0.97 (95% CI 0.87-1.08; p=0.55). All-cause mortality was 752 (9.7 percent) versus 788 (10.2 percent), RR 0.95 (0.86-1.05).

REDUCE-IT: positive, with a disputed comparator oil

Bhatt 2019 randomized 8,179 statin-treated patients with elevated triglycerides and established cardiovascular disease (70.7 percent) or diabetes plus other risk factors to highly purified EPA (icosapent ethyl) or a mineral-oil placebo; median follow-up 4.9 years. The primary endpoint occurred in 17.2 versus 22.0 percent, HR 0.75 (95% CI 0.68-0.83), cardiovascular death in 4.3 versus 5.2 percent (HR 0.80; 0.66-0.98). Hospitalizations for atrial fibrillation or flutter were more frequent with EPA (3.1 versus 2.1 percent). The placebo is disputed: in a biomarker analysis (Ridker 2022), LDL cholesterol rose by 10.9 percent and hsCRP by 21.9 percent after twelve months with mineral oil, while hardly anything changed with EPA (LDL minus 1.2 percent). The authors themselves call the significance of this for the overall result uncertain; the debate about the choice of placebo continues (Finocchiaro 2026).

PISCES: fish oil in dialysis patients

Lok 2026 (N Engl J Med, online since November 2025) randomized 1,228 hemodialysis patients in Canada and Australia to fish oil or a corn-oil placebo; follow-up about 3.5 years. The rate of major cardiovascular events was 0.31 versus 0.61 per 1,000 patient-days, HR 0.57 (95% CI 0.47-0.70), i.e. 43 percent lower. In dialysis patients, most cardiovascular trials had previously been neutral (Mazón-Ruiz 2026). The authors limit their conclusion to hemodialysis.

DO-HEALTH: epigenetic clocks

DO-HEALTH (Bischoff-Ferrari 2020) followed 2,157 people aged 70 and over for three years. Epigenetic clocks were measured retrospectively in 777 participants (Bischoff-Ferrari 2025): with omega-3, PhenoAge, GrimAge2 and DunedinPACE ran more slowly, equivalent to about three months (2.9 to 3.8 months) over the three years. The clocks are biomarkers; lifespan or disease were not measured with them.

Atrial fibrillation: a signal mainly at high dose and high risk

Abuknesha 2026 pooled 35 randomized trials with 37 data sets and 114,592 participants aged 50 and over (at least 500 mg of EPA plus DHA daily, at least 12 months). Only in the group at high cardiovascular risk and on a high dose above 1,500 mg daily was new-onset atrial fibrillation increased: OR 1.43 (95% CI 1.14-1.79), an absolute increase of 0.8 percentage points (0.40-1.1). The other groups were not significant (OR 1.07, 1.06 and 1.03).

Part of the context is who initiated the analysis: it was commissioned by GOED, the global trade association of omega-3 manufacturers, according to the press release without influence on the analysis. One author is chief medical officer of a company that sells omega-3 products, another holds shares in a provider of the omega-3 index test. Gencer 2021 reached a different result with seven large randomized cardiovascular trials and 81,210 participants: the risk was increased overall (HR 1.25), more clearly at more than 1 g daily (HR 1.49), but also significantly at 1 g daily or less (HR 1.12; 95% CI 1.03-1.22). The 2023 warning for omega-3 medicines is based on this and other meta-analyses (see Status, approval and legal situation).

Where the data stop

That 1 g of omega-3 daily prevents heart attacks. The finding from VITAL is a secondary result with a missed primary endpoint. As isolated proof, it is not robust.
That omega-3 protects against further events after a heart attack. The EMA removed this indication in 2019 after the medicines had proven not effective for it.
Whether common supplement doses of around 1 g daily promote atrial fibrillation. The meta-analyses contradict each other: Abuknesha 2026 saw a signal only in high-risk patients taking more than 1,500 mg daily, but the analysis was commissioned by the manufacturers' association GOED. Gencer 2021 found a 12 percent increased risk even at 1 g daily or less (HR 1.12). For these amounts, neither an all-clear nor a warning is established.
How much of the REDUCE-IT effect is due to EPA. LDL cholesterol and hsCRP rose under the mineral-oil placebo; how much this widened the gap between the groups is unresolved. The result also applies to highly purified EPA as a medicine, not to common fish oil products.
That the PISCES result applies beyond dialysis. Only hemodialysis patients were studied, and the authors limit their conclusion to this group.
That omega-3 measurably slows ageing. The DO-HEALTH finding on epigenetic clocks comes from a retrospective measurement in 777 of the 2,157 participants. The clocks are biomarkers; lifespan and disease were not measured with them.

Status, approval and legal situation

On 2019-03-29 the EMA confirmed that medicines containing omega-3 acid ethyl esters (EPA plus DHA, 1 g daily) are not effective for secondary prevention after a heart attack; this indication was removed. The approval for lowering triglycerides remains in place. Over-the-counter dietary supplements are not directly affected by this decision, but marketing them with claims of heart protection contradicts it.

Highly purified EPA (icosapent ethyl, Vazkepa) was approved in the EU in 2021 on the basis of REDUCE-IT to reduce cardiovascular events in statin-treated high-risk patients with elevated triglycerides. In its decision of 2022-02-17, Germany's Federal Joint Committee (G-BA) found an added benefit not proven and pointed to the mineral-oil placebo. Because the manufacturer and the statutory health insurers' umbrella association did not agree on a reimbursement price, Vazkepa has no longer been on the market in Germany since 2022-09-01.

On 2023-11-16, the marketing authorization holders, in agreement with the German regulator BfArM, informed healthcare professionals by letter that omega-3 acid ethyl ester medicines increase the risk of atrial fibrillation in a dose-dependent manner; this was based on an assessment by the EMA safety committee PRAC of several meta-analyses with more than 80,000 patients. In a communication on the same day, the BfR advised people with cardiovascular disease or risk factors to discuss taking omega-3 products with a physician; eating fish once or twice a week does not reach the amounts in question.

Safety

In STRENGTH, gastrointestinal side effects occurred in 24.7 percent versus 14.7 percent, meaning about ten percentage points more often at high dose. Atrial fibrillation occurs more often with omega-3 in a dose-dependent manner; whether amounts of around 1 g daily are already affected is judged differently by the meta-analyses (Abuknesha 2026, Gencer 2021). The BfR advises people with cardiovascular disease or risk factors to consult a physician. Low-quality oils can oxidize; at high doses, if you take anticoagulants or before surgery, consult a physician.

BK-Score Well supported

Human evidence		8
Mechanism		8
Safety data		9
Hype gap		6
Track record of use		10

Large randomized trials (including VITAL, REDUCE-IT, STRENGTH) with hard endpoints exist – but their results partly contradict each other. Mechanism and safety are well studied; much more is claimed in marketing than the studies support.

The score rates the state of knowledge, not the substance. A high safety-data value means well studied – not harmless. A high track-record value means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about omega-3 (EPA/DHA)

Does omega-3 really work for the heart?

The three large randomized trials VITAL, STRENGTH and ASCEND each missed their primary endpoint. Neither in the general population nor in people with diabetes nor in statin-treated high-risk patients could a reduction in major cardiovascular events be shown. Two other trials were positive: REDUCE-IT reduced major events by 25 percent with highly purified EPA in high-risk patients, although against a disputed mineral-oil placebo, and PISCES found 43 percent fewer major cardiovascular events with fish oil in dialysis patients. The lowering of elevated triglycerides remains well supported.

What did VITAL show about heart attacks?

As a secondary finding, VITAL reported a hazard ratio of 0.72 for total heart attacks. However, this finding comes from a secondary analysis, while the prespecified primary endpoint was missed, with a hazard ratio of 0.92 and a p-value of 0.24. As stand-alone proof of effect, it is not robust.

Does omega-3 make sense after a heart attack?

On March 29, 2019, the EMA confirmed that omega-3 acid ethyl ester medicines at 1 g daily are not effective in preventing further heart problems after a heart attack. This indication was removed. Only the approval for lowering elevated triglycerides remained. Over-the-counter dietary supplements are not directly affected by this decision.

Can omega-3 trigger atrial fibrillation?

The studies point to a dose-dependent increase in risk; they disagree about common amounts. A meta-analysis of 35 randomized trials with 114,592 participants (Abuknesha 2026) found new-onset atrial fibrillation increased only in people at high cardiovascular risk and at doses above 1,500 mg daily, with an odds ratio of 1.43 and an absolute increase of 0.8 percentage points. It was commissioned by the omega-3 manufacturers' trade association (GOED), and two authors have business ties to omega-3 companies. An earlier meta-analysis (Gencer 2021, 7 trials, 81,210 participants) found the risk increased by 12 percent even at 1 g daily or less. Since November 2023, omega-3 medicines carry a warning, and the German Federal Institute for Risk Assessment (BfR) advises people with heart disease or risk factors to discuss omega-3 products with a physician.

What side effects does omega-3 have?

In the high-dose STRENGTH trial, gastrointestinal complaints occurred in 24.7 percent versus 14.7 percent with the comparator oil, meaning about ten percentage points more often. In addition, there is an increased risk of atrial fibrillation, most pronounced at high doses and high cardiovascular risk. Low-quality oils can oxidize; if you take blood thinners, consult a physician.

Which doses were studied in the trials?

VITAL and ASCEND each tested 1 g of marine omega-3 daily against placebo and olive oil, respectively. STRENGTH tested 4 g of omega-3 carboxylic acid daily against corn oil. The meta-analysis on atrial fibrillation included studies from 500 mg of EPA plus DHA daily. Gram doses come from clinical questions; dietary recommendations are well below that, with EFSA setting an adequate intake of 250 mg of EPA plus DHA daily for adults. No usage recommendation follows from this.

The podcast episode (in German)

Episode 42

Omega-3: the fatty acids for a long life, fact-checked

The podcast by Paul Höser (Episode 42) · with Paul & Paula. The whole scientific detective story: from the observations of the Inuit through the years of null studies to the comeback with REDUCE-IT (Bhatt, NEJM 2019) and VITAL (Manson, NEJM 2019) – and the first randomized anti-aging evidence ever: in the DO-HEALTH study (Bischoff-Ferrari, Nature Aging 2025), 1 g of omega-3 daily slowed, in a retrospective measurement in 777 participants, the epigenetic clocks. Plus the omega-3 index (target 8–11 %), EPA vs. DHA, quality (TOTOX, algae oil) and an honest look at the atrial fibrillation debate. Information only – not medical advice, no dosage or usage recommendation.

Listen on Spotify

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Related topicCoenzyme Q10 (Ubiquinol)

Sources

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Information only, not medical advice and no usage or dosage recommendation. Prescription and unapproved drugs belong in the hands of a physician. Last updated: 2026-11-13.