NutriDex

The Supplement Research Compendium
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Omega-3 (EPA/DHA)

Fish/algal oil

Essential fatty acids for heart, brain, and inflammation.

Strong evidence 🫀Heart & Metabolic🧠Nootropic

✚ Updated · How we grade evidence

Evidence tier
Strong
Research weight
Citations
20 verified / 20
Classification
Heart & Metabolic
❝
What the evidence says. Graded strong for lowering triglycerides (consistent RCTs and an authorised EFSA claim) and for prescription high-dose EPA in high-risk heart patients (REDUCE-IT); benefit for primary prevention in already-healthy people is weak — VITAL and STRENGTH were neutral. (Strong evidence: Multiple high-quality RCTs / meta-analyses with consistent effects.)

What is Omega-3 (EPA/DHA)?

Omega-3 (EPA/DHA) (Fish/algal oil) is a heart and metabolic supplement used for lower triglycerides. NutriDex grades the human evidence as Strong. EPA and DHA are long-chain omega-3 fatty acids that the body cannot efficiently synthesize. High-dose omega-3 reliably lowers triglycerides (20–30%) and reduces inflammatory markers. Cardiovascular outcome trials are mixed — REDUCE-IT showed benefit with high-dose EPA, while others (STRENGTH, VITAL) were neutral. Higher-dose EPA-predominant formulas show modest antidepressant effects. DHA is structurally vital for the brain and retina, particularly during development.

Purported Benefits

✓Lower triglycerides
✓Anti-inflammatory
✓Brain & eye health
✓Mood support

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Triglyceride loweringMany RCT meta-analyses show ~20-40 mg/dL triglyceride reductions, dose-dependent above 2 g/day; EFSA-authorized claim. Strong ↑ benefit · moderate 5
Cardiovascular eventsHigh-dose EPA (REDUCE-IT) cut events 25% but VITAL/Cochrane were neutral; pooled effect small with atrial-fibrillation signal. Mixed ↔ mixed · small 6
Depression / moodEPA-predominant formulas (>=60% EPA, 1-2 g/day) show modest antidepressant effect; doses >=2 g/day no better. Moderate ↑ benefit · small 3
Cognitive decline preventionCochrane meta-analysis of 38 RCTs found little/no effect on cognitive impairment or global cognition (moderate certainty). Moderate — no effect · negligible 1
Preterm birth reductionCochrane review of 70 RCTs found ~11% fewer births before 37 wk and ~42% fewer before 34 wk. Moderate ↑ benefit · moderate 1
Atrial fibrillation (safety)Meta-analyses show raised AF risk (RR ~1.25), greatest above 1 g/day. Moderate ⚠ risk · small 2
Dry eye diseaseDREAM RCT (535 patients) found 3 g/day no better than placebo over 12 months. Moderate — no effect · negligible 1

Dosing & Compounds

Typical Dose
1–2 g combined EPA+DHA/day; up to 4 g (Rx) for high triglycerides.
Active Compounds
EPA (eicosapentaenoic acid)DHA (docosahexaenoic acid)

Safety & Cautions

Safe at typical doses. Fishy aftertaste and mild GI upset are common. High doses (>1 g/day) modestly raise the risk of atrial fibrillation — an irregular heartbeat — with the largest signal at higher intakes (pooled RCTs, RR ~1.25). May increase bleeding risk; tell your surgeon before procedures. Educational only — always check with your doctor or pharmacist before combining Omega-3 (EPA/DHA) with any medicine.

Omega-3 (EPA/DHA) drug interactions

Known or theoretical interactions between Omega-3 (EPA/DHA) and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Omega-3 (EPA/DHA) with any medicine.

Monitor
Blood thinners (warfarin, DOACs)
High-dose fish oil may slightly add to bleeding risk alongside blood thinners.
Omega-3s reduce platelet aggregation with mild antithrombotic action that can compound anticoagulants. NIH ODS — Omega-3

Key Studies ★ 20 studies

Meta-analysis Kelaiditis 2023 (PLEFA meta-analysis) ✓ PubMed
Meta-analysis of 10 RCTs (1,426 participants) found EPA-enriched omega-3 (>=60% EPA, 1 to <2 g/day) significantly reduced depression severity, while doses >=2 g/day showed no significant benefit.
Meta-analysis Bafkar 2024 (BMC Psychiatry dose-response meta-analysis) ✓ PubMed
Dose-response meta-analysis of 23 RCTs (2,189 participants) found omega-3 moderately reduced anxiety symptoms (SMD -0.70 per 1 g/day), with greatest effect around 2 g/day; GRADE certainty was low.
Meta-analysis Yang 2023 (JAHA) ✓ Full text
Continuous dose-response meta-analysis of 90 RCTs (n=72,598) found omega-3 intake above 2 g/day had a near-linear association with reductions in triglycerides and non-HDL cholesterol, supporting medium-to-high doses for dyslipidemia.
Meta-analysis Marine omega-3 & metabolic syndrome 2025 (Nutrients/PMC) ✓ Full text
Systematic review and meta-analysis of RCTs (search through June 2024) found marine-derived EPA/DHA supplementation improved metabolic syndrome components, including triglyceride-lowering and anti-inflammatory effects, versus placebo.
Meta-analysis Zhang 2025 (Food Sci Nutr) ✓ Full text
Dose-response meta-analysis of RCTs in coronary heart disease patients found omega-3 intake produced a statistically significant reduction in triglyceride levels (moderate-quality evidence) alongside effects on plaque volume.
Meta-analysis Gencer 2021 (Circulation meta-analysis) ✓ PubMed
Pooled meta-analysis of 7 cardiovascular-outcome RCTs (81,210 patients) found marine omega-3 supplementation raised atrial fibrillation risk (RR 1.25), with the increase greatest at higher doses (>1 g/day).
Meta-analysis Medicine 2022 (Pei meta-analysis) ✓ PubMed
Meta-analysis of 28 RCTs (136,965 individuals) found omega-3 supplementation modestly reduced major cardiovascular events (RR 0.94) and cardiac death (RR 0.92), with no effect on all-cause mortality, MI, or stroke.
Meta-analysis Yang 2022 (Front Nutr meta-analysis) ✓ PubMed
Meta-analysis of 32 RCTs (15,903 participants) found omega-3 monotherapy markedly lowered triglycerides (mean difference -39.8 mg/dL) in hypertriglyceridemia, with reductions also seen when combined with statins (-29.6 mg/dL).
Meta-analysis Khan et al. 2021 ✓ PubMed
Across 38 RCTs (149,051 participants), omega-3 FAs reduced CV mortality (RR 0.93), nonfatal MI (RR 0.87), CHD events (RR 0.91), MACE (RR 0.95), and revascularization (RR 0.91); effects were stronger for EPA monotherapy than EPA+DHA, but omega-3 increased incident atrial fibrillation (RR 1.26) and EPA monotherapy increased bleeding (RR 1.49).
Meta-analysis Brainard et al. 2020 ✓ PubMed
Meta-analysis of 38 RCTs (49,757 participants) found long-chain omega-3 has little or no effect on new neurocognitive illness (RR 0.98), new cognitive impairment (RR 0.99), or global cognition (MMSE), indicating supplements do not protect older adults from cognitive decline (moderate-certainty evidence).
Meta-analysis Liao 2019 meta-analysis ✓ PubMed
EPA-dominant supplements showed small antidepressant effect.
Meta-analysis Hu et al. 2019 ✓ PubMed
Pooled analysis of 13 RCTs (127,477 participants) found marine omega-3 supplementation reduced MI (RR 0.92), CHD death (RR 0.92), total CHD (RR 0.95), CV death (RR 0.93), and total CVD (RR 0.97), even excluding REDUCE-IT; risk reductions were linearly dose-dependent.
Agency / regulator AHA Science Advisory 2019 ✓ PubMed
Strong evidence for triglyceride lowering.
RCT Peterson 2025 (JAHA, REDUCE-IT secondary analysis) ✓ Full text
In statin-treated patients with elevated triglycerides, icosapent ethyl reduced the primary composite cardiovascular endpoint regardless of baseline LDL-C (HR 0.66 [95% CI 0.50-0.87] if LDL-C <55 mg/dL; HR 0.76 [95% CI 0.69-0.85] if >=55 mg/dL; P-interaction=0.40).
Agency / regulator EFSA NDA Panel (health claim) ✓ Source
EFSA authorized the claim that DHA contributes to maintenance of normal blood triglyceride levels, concluding intakes of 2-4 g/day EPA and DHA are needed to achieve the triglyceride-lowering effect.
RCT REDUCE-IT 2019 ✓ PubMed
4g/day icosapent ethyl cut major cardiac events 25% in high-risk patients.
rct VITAL 2019 (Manson, NEJM) ✓ PubMed
Primary-prevention RCT in 25,871 generally healthy US adults found 1 g/day marine n-3 fatty acids did not significantly reduce major cardiovascular events (HR 0.92) or invasive cancer (HR 1.03) over 5.3 years versus placebo.
rct DREAM 2018 (NEJM) ✓ PubMed
Multicenter RCT in 535 patients with moderate-to-severe dry eye disease found 3 g/day omega-3 (2000 mg EPA/1000 mg DHA) was no better than placebo for relieving signs or symptoms over 12 months.
systematic_review Abdelhamid 2020 (Cochrane CD003177.pub5) ✓ PubMed
Cochrane systematic review of 86 RCTs (162,796 participants) found increasing long-chain omega-3 has little or no effect on all-cause or cardiovascular mortality but slightly reduces coronary heart disease mortality and events and lowers triglycerides (moderate- to low-certainty evidence).
systematic_review Middleton 2018 (Cochrane CD003402.pub3) ✓ PubMed
Cochrane review of 70 RCTs (19,927 women) found omega-3 supplementation during pregnancy reduced preterm birth before 37 weeks by about 11% (RR 0.89) and early preterm birth before 34 weeks by about 42% (RR 0.58).
20 sources cited · 20 verified Search all studies on PubMed ↗

Common questions about Omega-3 (EPA/DHA)

What is Omega-3 (EPA/DHA) used for?

Omega-3 (EPA/DHA) is most often taken for Lower triglycerides, Anti-inflammatory, Brain & eye health, Mood support. Essential fatty acids for heart, brain, and inflammation.

Does Omega-3 (EPA/DHA) work — what does the evidence say?

Strong evidence. Multiple high-quality RCTs / meta-analyses with consistent effects. EPA and DHA are long-chain omega-3 fatty acids that the body cannot efficiently synthesize. High-dose omega-3 reliably lowers triglycerides (20–30%) and reduces inflammatory markers. Cardiovascular outcome trials are mixed — REDUCE-IT showed benefit with high-dose EPA, while others (STRENGTH, VITAL) were neutral. Higher-dose EPA-predominant formulas show modest antidepressant effects. DHA is structurally vital for the brain and retina, particularly during development.

What is the typical dose of Omega-3 (EPA/DHA)?

1–2 g combined EPA+DHA/day; up to 4 g (Rx) for high triglycerides.

Is Omega-3 (EPA/DHA) safe? Any cautions or side effects?

Safe at typical doses. Fishy aftertaste and mild GI upset are common. High doses (>1 g/day) modestly raise the risk of atrial fibrillation — an irregular heartbeat — with the largest signal at higher intakes (pooled RCTs, RR ~1.25). May increase bleeding risk; tell your surgeon before procedures.

How many studies support Omega-3 (EPA/DHA)?

NutriDex cites 20 sources for Omega-3 (EPA/DHA), graded "Strong".

Does Omega-3 (EPA/DHA) interact with any medications?

Yes — known or theoretical interactions include: Blood thinners (warfarin, DOACs) (monitor). This is educational and not exhaustive; always check with your doctor or pharmacist before combining Omega-3 (EPA/DHA) with any medicine.

Cite this page
APA

Peh, D. (2026). Omega-3 (EPA/DHA) (Fish/algal oil): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/omega3

BibTeX
@misc{nutridex_omega3,
  author       = {Peh, Daryl},
  title        = {Omega-3 (EPA/DHA) (Fish/algal oil): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/omega3},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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