Lipids & Fatty Acids

Omega-3 Fatty Acids

Also known as: EPA, DHA, Fish oil, Eicosapentaenoic acid, Docosahexaenoic acid

Essential fats from fish and algae (EPA and DHA) that support heart, brain, and eye health.

By IngredientWiki Editorial Team
Fact-checked by IngredientWiki Editorial Team
Updated 2026-09-25
3 min read

In short

Omega-3 fatty acids are a family of polyunsaturated fats that the body cannot make efficiently and must come from food or supplements. The two with the strongest evidence are EPA and DHA, found mainly in fatty fish and algal oil. Omega-3s are structural components of cell membranes, especially in the brain and retina, and are among the most popular supplements in the United States.

EPA and DHA come mainly from fatty fish and algae; ALA comes from plants
DHA is a major structural fat in the brain and retina
Strongest evidence: lowering very high triglycerides
No official RDA; adequate intake for ALA is 1.6 g (men) / 1.1 g (women) daily

What is Omega-3 Fatty Acids?

Omega-3s are essential fatty acids, meaning the body needs them but cannot synthesize them. There are three main types: ALA from plants, and EPA and DHA from marine sources. The body converts only a small fraction of ALA into EPA and DHA, so direct intake of EPA/DHA — from fish, seafood, or supplements — matters. Omega-3s are incorporated into cell membranes throughout the body and are especially concentrated in the brain and retina, where DHA makes up a substantial share of structural fat.

Where it comes from

Natural sources

Fatty fish: salmon, mackerel, sardines, herring, anchovies
Fish oil and krill oil supplements
Algal oil (the original source of EPA/DHA, popular with vegans)
ALA sources: flaxseed, chia seeds, walnuts, canola oil

What it does in products

Benefits

Lowering high triglycerides

strong evidence

EPA/DHA reliably lower blood triglycerides at doses of 2–4 grams daily, and prescription omega-3 products are FDA-approved for very high triglycerides.

Heart health

strong evidence

The FDA allows a qualified health claim that EPA and DHA may reduce the risk of coronary heart disease. Meta-analyses find a modest reduction in cardiovascular events from higher-dose supplementation.

Pregnancy and infant development

moderate evidence

DHA accumulates in the fetal brain during the third trimester, and adequate maternal intake supports infant visual and cognitive development. Prenatal supplements commonly include 200–300 mg DHA.

Joint comfort

moderate evidence

Because omega-3s modulate inflammatory signaling, some trials find modest improvements in joint pain and stiffness, particularly in rheumatoid arthritis, where evidence is stronger.

Side effects & safety

Fishy burps and aftertaste (common)Enteric-coated capsules, refrigerated fish oil, or algal oil usually prevent this.

Mild digestive upset (uncommon)Taking fish oil with meals reduces nausea and reflux.

Slightly increased bleeding tendency (rare)Relevant mainly at doses above 3 g per day or when combined with anticoagulant medication.

Safety considerations

DHA is recommended during pregnancy. Choose molecularly distilled or third-party-tested products, and limit intake from large predatory fish due to mercury.
High-dose omega-3s can add to the effect of blood thinners such as warfarin; doses above 3 g per day should be discussed with a doctor.
Omega-3s can slightly raise LDL cholesterol in some people, an effect usually considered clinically minor.
Not for: Allergy to fish or shellfish (use algal oil instead)

How it's used

In supplements

General health: 250–500 mg combined EPA+DHA daily is common. For triglycerides: 2–4 g daily under medical supervision. Check the label for EPA and DHA content, not total fish oil weight.

Regulatory status

Dietary supplement under DSHEA. The FDA permits qualified health claims for EPA/DHA and reduced risk of coronary heart disease. Prescription-strength omega-3 ethyl esters are approved drugs for very high triglycerides.
GRAS (generally recognized as safe) for food use.

Fish oil vs krill oil vs algal oil

Fish oil is the classic and most studied source of EPA/DHA. Krill oil delivers omega-3s bound to phospholipids and also contains astaxanthin; it may be absorbed somewhat more efficiently, but far fewer long-term trials exist. Algal oil is the vegan alternative — algae are where fish get their EPA/DHA in the first place — and has a comparable effect on blood levels at equivalent doses.

Frequently asked questions

How much omega-3 should I take daily?

For general wellness, 250–500 mg of combined EPA+DHA is a common target; official bodies generally recommend at least 2 servings of fatty fish per week. If your goal is lowering triglycerides, clinical doses of 2–4 g daily are used, but that should be done under medical supervision.

What is the difference between EPA and DHA?

Both are long-chain marine omega-3s. DHA is more concentrated in brain and retinal tissue and is emphasized during pregnancy and early life, while EPA is more closely associated with anti-inflammatory signaling and triglyceride lowering. Most supplements contain both.

Is fish oil safe to take long-term?

For most people, yes — fish oil has decades of safety data at doses up to 3 g per day. Choose products tested for mercury, PCBs, and oxidation, and check with your doctor if you take blood thinners or have a fish allergy.

The bottom line

Omega-3s are essential fats with solid evidence for heart and triglyceride benefits, and DHA matters during pregnancy and early life. For most people, 250–500 mg of EPA+DHA daily from fish, algal, or krill oil is a reasonable supplement strategy, while 2–4 g doses are reserved for medical purposes.

References

Omega-3 Fatty Acids — Health Professional Fact Sheet. NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
Omega-3 Supplements: In Depth. NCCIH (National Institutes of Health). https://www.nccih.nih.gov/health/omega3-supplements-in-depth
FDA Announcement: Qualified Health Claim for EPA and DHA Omega-3s. U.S. Food and Drug Administration. https://www.fda.gov/food/cfsan-constituent-updates/fda-announces-new-qualified-health-claims-epa-and-dha-omega-3-consumption-and-risk-hypertension-and
Fish Oil — PubChem compound records for eicosapentaenoic acid. PubChem (National Library of Medicine). https://pubchem.ncbi.nlm.nih.gov/compound/446284