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Educational guide · 14 min read

Omega-3, explained properly.

Omega-3 is the most-studied essential fatty acid in cardiovascular and brain health — and the most-supplemented. But the EPA-to-DHA ratio, the molecular form (TG vs ethyl ester), and the freshness of the oil make a 5x difference in what reaches your bloodstream. Most supplements on Australian shelves are oxidized by the time you open the bottle.

Last updated: August 23, 2026 · Sources: NIH ODS Omega-3, Mozaffarian 2005, Bhatt 2019 REDUCE-IT, Calder 2017

What omega-3 actually is

Omega-3 is a family of polyunsaturated fatty acids (PUFAs) with the first double bond at the third carbon from the methyl end. The three most clinically relevant are:

The body cannot synthesize EPA or DHA from scratch — they must come from diet (or supplements). Modern Western diets are omega-6 dominant (vegetable oils, processed food) at a 15-20:1 ratio vs omega-3, vs an evolutionary ratio closer to 1:1. This imbalance is implicated in chronic inflammation.

The bottom line: for cardiovascular and anti-inflammatory effects, the active ingredients are EPA and DHA — not ALA. If you take plant-based omega-3 (flaxseed oil), your body converts only ~5-10% to EPA and barely any to DHA. For meaningful EPA/DHA intake, eat fatty fish or take a marine-source supplement.

How EPA and DHA work in the body

EPA and DHA get incorporated into cell membranes throughout the body, where they do at least four clinically-meaningful things:

  1. Membrane fluidity. DHA has 6 double bonds (vs 2 for saturated fats), giving cell membranes the flexibility to function. Brain neurons are ~15% DHA by dry weight.
  2. Anti-inflammatory eicosanoids. EPA is the substrate for series-3 prostaglandins and series-5 leukotrienes — both less inflammatory than the omega-6-derived equivalents. Resolvins and protectins from DHA/EPA actively terminate inflammation.
  3. Triglyceride lowering. 3-4 g/day EPA+DHA reduces fasting triglycerides by 25-30% — comparable to prescription fibrates. The effect is dose-dependent and well-replicated.
  4. Blood pressure reduction. ~2-3 mmHg systolic reduction at 3+ g/day EPA+DHA per Miller 2014 meta-analysis.
  5. Platelet function. At pharmacological doses (>3 g/day), EPA/DHA mildly inhibit platelet aggregation — the basis for the secondary prevention claim.
  6. Cardiac rhythm. Higher omega-3 tissue levels are associated with lower risk of fatal arrhythmias — particularly in post-MI patients.

The 5 forms of omega-3 supplements, compared

The form determines both absorption and price. Most "fish oil" on the shelf is one of these five.

1. Triglyceride (TG) form

Best absorbed

The natural form — EPA and DHA bound to a glycerol backbone, just like in fish flesh. Neubronner 2011 RCT: 70% higher plasma EPA+DHA after 2 weeks vs ethyl ester at the same dose. The premium form; costs 2-3x more.

Best for: anyone who wants maximum absorption, higher-dose users (3+ g/day), people with malabsorption.

2. Ethyl ester (EE) form

Most common

EPA and DHA bound to ethanol instead of glycerol. Manufactured by molecular distillation to concentrate EPA/DHA. Cheaper, but requires enzymatic re-esterification in the gut to be absorbed — ~70% the bioavailability of TG per Neubronner 2011.

Best for: budget users, maintenance dosing (1-2 g/day), prescription Vascepa (icosapent ethyl).

3. Phospholipid form (krill oil)

Premium marine

EPA and DHA bound to phospholipids (mainly phosphatidylcholine) from Antarctic krill. Marketing claims of superior absorption are partially supported (small RCTs show ~1.5x plasma levels vs fish oil at low doses) but absolute EPA+DHA per softgel is much lower than fish oil — you'd need 4-5 krill softgels to match one fish oil softgel.

Best for: people who cannot tolerate fish oil, vegetarians (some krill oil is sustainably certified).

4. Re-esterified TG (rTG)

Concentrated natural

The form made by taking ethyl ester and re-attaching EPA/DHA to a glycerol backbone — same bioavailability as natural TG per Dyerberg 2010. Many "premium" fish oil brands use rTG. Cost-effective middle ground.

Best for: high-dose users who want TG form at lower cost.

5. Algal oil (vegan)

Vegan-friendly

DHA (and sometimes EPA) extracted from microalgae. The original source — fish accumulate omega-3 by eating algae. Smit 2010 RCT showed algal DHA raises plasma DHA as effectively as fish-derived DHA. Most vegan products are DHA-only; a few brands offer algal EPA.

Best for: vegans, vegetarians, people avoiding fish for religious/cultural reasons.

How much omega-3 do you actually need?

The dose depends entirely on your goal. There is no single "right" amount.

Goal EPA+DHA dose Evidence
General health / heart disease prevention250–500 mg/dayMozaffarian 2005, AHA
Triglyceride lowering2000–4000 mg/dayMultiple RCTs (skeletal)
Secondary CV prevention (post-MI)1000 mg EPA/dayREDUCE-IT 2019
Pregnancy / fetal brain development200–300 mg DHA/dayColetta 2010 meta-analysis
Rheumatoid arthritis / inflammation2700 mg+ EPA+DHA/dayGoldberg 2007
Dry eye syndrome1000 mg EPA+DHA/dayAREDS2 2013

Source: NIH ODS Omega-3 Fact Sheet. The FDA classifies doses ≤ 3000 mg/day as GRAS (Generally Recognized As Safe). Above 3000 mg/day, FDA requires monitoring — antiplatelet effects become measurable.

EPA vs DHA: which do you want?

Most "fish oil" capsules contain both EPA and DHA, but the ratio matters. The 2019 REDUCE-IT trial used an EPA-only product (icosapent ethyl / Vascepa) at 4 g/day and showed a 25% reduction in cardiovascular events — the strongest single supplement CV outcome ever. This was NOT replicated by mixed EPA+DHA trials at similar doses, suggesting EPA alone may be the active ingredient for cardiovascular outcomes.

Choose high-EPA when

  • Cardiovascular risk reduction (post-MI, high triglycerides)
  • Mood / depression (EPA has stronger antidepressant signal per Martins 2009)
  • Inflammation / autoimmune
  • Anti-inflammatory dosing (per REDUCE-IT)

Choose high-DHA when

  • Pregnancy / fetal brain development
  • Childhood cognitive development
  • Dry eye syndrome (AREDS2 used DHA-rich formula)
  • Age-related cognitive decline
  • Vegetarians / vegans (most algal oils are DHA-only)

Freshness and TOTOX — what most reviews miss

Fish oil is one of the few supplements where oxidation is a real, measurable safety issue. Oxidized omega-3 oils have been linked to increased lipid peroxidation, gut inflammation, and (paradoxically) increased cardiovascular risk. The industry has settled on two markers:

A 2015 Australian survey (Jackowski 2015, NZFSA data) found the average omega-3 supplement on Australian shelves had TOTOX > 30 — past IFOS limits. Look for brands that publish third-party IFOS certification on their product pages.

Smell test: open a softgel and smell the oil. Fresh omega-3 should smell like the sea — light, briny, not unpleasant. If it smells like old fish, varnish, or strong chemicals, it's oxidized. The smell test is imperfect but better than trusting the label.

The REDUCE-IT story (and the STRENGTH controversy)

The REDUCE-IT trial (Bhatt 2019, NEJM) tested icosapent ethyl (pure EPA, 4 g/day) in 8,179 patients with elevated triglycerides and cardiovascular disease or diabetes. Result: 25% relative risk reduction in major cardiovascular events vs placebo (mineral oil, which has its own issues).

The STRENGTH trial (Nicholls 2020, JAMA) tested a mixed EPA+DHA carboxylic acid formulation in 13,078 similar patients. Result: NO benefit. Trial stopped early for futility.

What does this mean for you?

  1. EPA alone (high-dose) appears to be the active ingredient for cardiovascular outcomes. Mixed EPA+DHA at similar doses may not work.
  2. REDUCE-IT's placebo was mineral oil — which raises LDL and may have exaggerated the active arm's benefit. The true effect is likely smaller than 25%.
  3. STRENGTH used a different formulation — corn oil placebo, EPA+DHA not pure EPA. Both trials have confounders.
  4. The honest answer: if you have established cardiovascular disease and elevated triglycerides, talk to your cardiologist about prescription icosapent ethyl (Vascepa). For primary prevention, a standard high-quality EPA+DHA fish oil at 1-2 g/day is reasonable.

Vegan and algal sources

Vegans and vegetarians can meet omega-3 needs through microalgae oil — the original source before fish accumulate it. Most algal products are DHA-only; algal EPA is rarer and more expensive.

What to pair with omega-3 (and what to avoid)

Pairs well

  • Vitamin E (mixed tocopherols) — natural antioxidant in the oil, prevents oxidation
  • Vitamin D3 — fat-soluble companion; both often in same softgel
  • Curcumin — synergistic anti-inflammatory effect
  • A meal containing fat — improves absorption 2-3 fold

Use caution

  • Anticoagulants (warfarin, apixaban, rivaroxaban) — high-dose omega-3 (>3 g/day) adds antiplatelet effect; monitor INR
  • Fish allergy — algal oil is the alternative
  • Pre-surgery — stop high-dose omega-3 1-2 weeks before major surgery
  • Refrigerated storage — slow oxidation; not required for IFOS-certified products but helps the rest

Frequently asked questions

▶ Does omega-3 really prevent heart attacks?

Mixed evidence. The 2019 REDUCE-IT trial showed pure EPA at 4 g/day reduced cardiovascular events 25% in high-risk patients. The 2020 STRENGTH trial with mixed EPA+DHA showed no benefit. The consensus for healthy adults: 250-500 mg/day EPA+DHA is reasonable for general heart health but don't expect dramatic reductions in cardiovascular events.

▶ How much fish do I need to eat to match a supplement?

Two servings of fatty fish per week (salmon, sardines, mackerel) gives roughly 250-500 mg EPA+DHA per day — equivalent to the AHA recommendation. Wild-caught salmon has more omega-3 than farmed (less, but still meaningful). For higher doses (1-3 g/day), food alone becomes impractical — you'd need to eat fish at every meal.

▶ Should I take omega-3 with food?

Yes — always with a meal containing fat. Omega-3 absorption improves 2-3x when taken with food (especially fat-containing food) per Neubronner 2011. Taking omega-3 on an empty stomach causes fishy burps in some users and reduces absorption significantly.

▶ Is krill oil better than fish oil?

Not really. Krill oil has slightly better absorption of EPA per mg, but each softgel contains much less EPA+DHA than fish oil — you'd need 4-5 krill softgels to match one fish oil softgel. The cost per mg of EPA+DHA is typically 2-3x higher for krill. Phospholipid form may have minor benefits for cell membrane integration, but the evidence is thin.

▶ Can I give omega-3 to my child?

Yes — DHA is critical for brain development. Pediatric dosing: infant formula with DHA (already mandatory in AU/EU), 50-100 mg DHA/day for toddlers, 250 mg combined EPA+DHA for school-age children. Avoid cod liver oil in young children due to vitamin A accumulation. Look for child-formulated omega-3 with IFOS certification.

▶ What about mercury in fish oil?

Modern molecular distillation removes heavy metals (mercury, lead, cadmium) below detectable limits in IFOS-certified brands. The mercury concern is overblown for supplements — far more mercury exposure comes from eating large predatory fish (tuna, swordfish, king mackerel). Stick with small fish (sardines, anchovies) for supplements and food.

References & sources

  1. NIH Office of Dietary Supplements — Omega-3 Fatty Acids Fact Sheet. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
  2. Mozaffarian D, Wu JH. (2011). Omega-3 fatty acids and cardiovascular disease: effects on risk factors, molecular pathways, and clinical events. Journal of the American College of Cardiology 58(20):2047-2067. doi.org/10.1016/j.jacc.2011.06.063
  3. Bhatt DL, et al. (2019). Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia (REDUCE-IT). New England Journal of Medicine 380(1):11-22. PMID: 30415628
  4. Nicholls SJ, et al. (2020). Effect of High-Dose Omega-3 Fatty Acids vs Corn Oil on Major Adverse Cardiovascular Events in Patients at High Cardiovascular Risk (STRENGTH). JAMA 324(22):2268-2280. PMID: 33190147
  5. Neubronner J, et al. (2011). Enhanced bioavailability of eicosapentaenoic acid and docosahexaenoic acid from a novel triglyceride formulation. Prostaglandins, Leukotrienes and Essential Fatty Acids 85(6):315-322. PMID: 21063442
  6. Calder PC. (2017). Omega-3 fatty acids and inflammatory processes: from molecules to man. Biochemical Society Transactions 45(5):1105-1115. doi.org/10.1042/BST20160474
  7. Examine.com — Omega-3 Fish Oil research review. examine.com
  8. International Fish Oil Standards (IFOS) program. nutrasource.ca
  9. Chemist Warehouse AU, iHerb, Amazon, Swisse AU, Blackmores AU, BioCeuticals AU, Ethical Nutrients, Herbs of Gold, Nature's Own, Vistra TH, Mega We Care, Thorne, Interpharma — product pages and price snapshots cited per row in the omega-3 comparison table.

Trusted brands we rate

These 10 brands are featured on every vitfacts.com comparison page. We track them for ingredient transparency, third-party testing, and Thailand availability.

Thorne Research

Since 1984

PREMIUM

While based in the US, Thorne is heavily imported and highly sought after by functional medicine practitioners globally—including in both Australia and Thailand. It is considered a gold standard due to its strict four-round testing protocol and complete absence of unnecessary fillers or binders.

TH: limited Search “omega 3 fish oil” ↗
Healthy Care

Since 2006

BUDGET

An Australian-made value brand founded in 2006, sold through Chemist Warehouse and major AU pharmacies. Part of the Nature's Care family (est. 1990), offering a wide mass-market supplement range covering fish oil, vitamins C/D, magnesium, probiotics, zinc, iron, ashwagandha, collagen, and CoQ10.

TH: limited Search “omega 3 fish oil” ↗

Why these 10? See the VitFacts editorial policy page (forthcoming) for the criteria — minimum 10 years of documented safety record, public certificate-of-analysis policy, and verifiable Thailand distribution.

Not medical advice. This article is for educational purposes only and does not constitute medical advice. Consult a qualified clinician before starting any new supplement, especially if you take anticoagulants, are pregnant or breastfeeding, or have a bleeding disorder.