Omega-3, -6 & -9 Fatty Acids: Your Complete Guide

The Quick Take

Omega-3s (EPA & DHA): The headline act. They support heart health, lower triglycerides, aid foetal and infant development, and may help with joint health, mood, and eye health. Best sources are oily fish or algal oil.

Omega-6s (linoleic acid): Also essential. Found mostly in nuts, seeds, and vegetable oils. They're not the enemy—adequate intake is actually linked to lower cardiovascular risk.

Omega-9s (oleic acid): Non-essential, meaning your body makes them. Great to eat through extra-virgin olive oil and nuts, but rarely worth supplementing.

For most people: Aim for two fish meals per week or about 250–500 mg of EPA+DHA daily (algal oil if you're vegan). For high triglycerides, medical-grade doses of 2 g or more daily under medical supervision.

What Are These Fatty Acids?

Omega-3:

• α-linolenic acid (ALA, from plants)

• Eicosapentaenoic acid (EPA, from marine sources)

• Docosahexaenoic acid (DHA, from marine sources)

• ALA is essential but poorly converted (only about 0–10%) to EPA and DHA

Omega-6:

• Linoleic acid (LA) is essential

• Arachidonic acid (AA) is made from LA in your body

Omega-9:

• Oleic acid (found in olive oil) and similar fats

• Useful but not essential—your body can make them

How Do They Work?

These fatty acids slot into your cell membranes and become signalling molecules called eicosanoids, resolvins, and protectins.

EPA and DHA tend to produce less inflammatory mediators and improve membrane fluidity—good news for heart rhythm, triglyceride levels, and possibly mood and vision.

LA (omega-6) is required for your skin barrier and normal growth. Despite the hype, adequate intake doesn't inherently "cause inflammation" in typical diets.

Omega-9 improves your lipid profile largely when it replaces saturated fat in your diet.

What Does the Science Say?

Strong and Consistent Evidence

Cardiovascular health and lipids: EPA and DHA lower triglycerides with a clear dose-response relationship (about 15–30% reduction at 2–4 g daily). A purified EPA drug called icosapent ethyl at 4 g daily reduced cardiovascular events in high-risk patients already on statins.

Pregnancy and infancy: DHA supports foetal brain and retina development, may reduce early preterm birth risk, and improve infant visual outcomes.

General mortality: Higher circulating omega-3 levels are associated with lower all-cause and cardiovascular mortality in large population studies.

Promising but Mixed Results

Primary prevention: Some trials show modest benefit signals, though effect sizes are small.

Mood and cognition: Small to moderate effects in certain depression subgroups (especially with EPA-leaning blends). Evidence for preventing cognitive decline is mixed.

Insufficient or Low Yield

Omega-9 supplementation: Dietary sources are excellent; capsules add little beyond extra calories.

"Fixing" the omega-6 to omega-3 ratio: Getting enough total omega-3s matters far more than chasing a specific ratio.

Is Omega Supplementation Right for You?

Great Fit If You're:

• Getting little to no fish in your diet

• Pregnant or breastfeeding

• Dealing with high triglycerides

• Experiencing ocular surface issues (dry eyes)

• Managing joint stiffness

• An older adult aiming for cardiovascular risk reduction alongside standard medical care

Lower Priority If You're:

• Already eating oily fish one to two times per week and otherwise healthy

• Expecting weight loss or "anti-inflammatory cure-alls" from capsules alone

What Results Can You Expect?

250–500 mg daily EPA+DHA: Foundational support for heart, brain, and eye health.

2–4 g daily EPA+DHA (medical-grade): Substantial triglyceride reduction. Event reduction has been demonstrated with 4 g daily purified EPA in specific high-risk groups on statins.

Symptom improvements: Changes in dry eye, morning joint stiffness, or mood are modest and typically need 8–12 weeks to become noticeable.

Dosage and Forms

For Everyday Health

EPA+DHA: 250–500 mg daily total. Eat fatty fish like salmon, sardines, or mackerel, or take algal oil (vegan DHA with or without EPA).

ALA: One to two tablespoons of ground flax or chia seeds, or a handful of walnuts helps—but don't rely on ALA alone to make all your EPA and DHA.

For Clinical Targets

High triglycerides: 2–4 g daily EPA+DHA (ethyl-ester or triglyceride forms) under medical guidance. The strongest evidence is for EPA-only 4 g daily prescription in secondary prevention.

Omega-6

Aim for about 5–10% of calories from LA. A normal varied diet with nuts, seeds, and plant oils usually covers this easily.

Omega-9

Get it from foods like extra-virgin olive oil, almonds, and hazelnuts. No standard supplemental dose needed.

Forms and Absorption Notes

Triglyceride (TG) or re-esterified TG oils: Show slightly better absorption than ethyl-esters unless taken with meals.

Phospholipid (krill): Performs similarly but contains lower EPA and DHA content and is usually pricier.

Safety and Side Effects

Generally well tolerated.

Common issues: Fishy burps and digestive upset—take with meals or use enteric-coated or lemon-flavored oils.

Bleeding risk: Low at typical doses, but use caution if you're on anticoagulants. Ask your doctor, especially if taking above 1 g daily.

Contaminants and oxidation: Choose brands with third-party testing. Keep bottles cool and in the dark, and use within 60–90 days of opening.

What to Look for When Buying

✓ EPA+DHA clearly listed on the label: Not just "fish oil mg." You want at least 250–500 mg daily combined as baseline.

✓ Third-party testing: Look for IFOS/GOED monograph, NSF/Informed-Choice, or equivalent. Check TOTOX and peroxide numbers when available.

✓ Sustainability: Small pelagic fish (anchovy, sardine), MSC or Friend of the Sea certification, or algal oil.

✓ Form and freshness: Triglyceride or re-esterified TG forms; dark glass or high-barrier capsules; recent manufacture date.

✓ Vegan options: Algal oil with 250–400 mg DHA per capsule, ideally with added EPA.

✗ Skip: "Omega-3-6-9" combo capsules that underdose EPA and DHA while adding unnecessary omega-9.

The Final Word

Prioritize EPA and DHA from food or a quality supplement—they're the proven performers in the omega family. Keep omega-6 coming from wholesome plant foods and don't fear it. Get your omega-9 from your olive oil bottle, not a capsule.

Most adults do well with 250–500 mg EPA+DHA daily. Those with high triglycerides may benefit from clinical-grade 2–4 g daily under medical supervision. Eat fish, mind quality, and let supplements support (not replace) good nutrition.

References

Research supporting this guide includes the American Heart Association Science Advisory on omega-3 fatty acids for hypertriglyceridemia management and event reduction with icosapent ethyl (Circulation, 2019–2021); the REDUCE-IT Trial by Bhatt et al. showing cardiovascular risk reduction with 4 g daily icosapent ethyl in patients on statins (New England Journal of Medicine, 2019); Cochrane Reviews on omega-3s for cardiovascular outcomes and pregnancy/infant development; WHO/FAO guidance on fats and fatty acids in human nutrition with intake recommendations; and meta-analyses examining omega-3s for depression, dry eye disease, and triglyceride dose-response relationships.