Omega-3 (EPA & DHA) for Longevity & Health

Omega-3 fatty acids are a family of polyunsaturated fats, the most studied of which are the long-chain marine forms EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), found in oily fish and fish-oil supplements. They are “essential” in the sense that the body cannot make them efficiently and largely depends on diet. For healthspan, interest centres on their roles in cardiovascular function, triglyceride metabolism, the brain, and inflammation.

The honest summary is that omega-3s are a well-established, generally safe nutrient with a clear effect on blood triglycerides — but the evidence for hard outcomes like heart attacks, dementia, or depression is mixed and dose-dependent. This page lays out what is reasonably supported and what remains uncertain, rather than treating fish oil as either a cure-all or a placebo.

How it works

EPA and DHA are incorporated into cell membranes throughout the body, where they alter membrane fluidity and serve as precursors for signalling molecules. They compete with the omega-6 fatty acid arachidonic acid in the production of eicosanoids (prostaglandins, thromboxanes, leukotrienes), generally shifting the balance toward less inflammatory mediators. EPA and DHA are also substrates for specialised pro-resolving mediators — resolvins, protectins, and maresins — that help actively switch off inflammation rather than merely suppress it.

The most consistent and best-quantified effect is on lipids: at gram-level doses, omega-3s reduce hepatic production of very-low-density lipoprotein and lower circulating triglycerides, typically by around 15% in a dose-dependent way. DHA tends to lower triglycerides somewhat more than EPA but can modestly raise LDL cholesterol, which is one reason formulation and ratio matter.

Evidence by use-case

Cardiovascular disease: this is where the data are most debated. Large primary-prevention trials in general or diabetic populations (VITAL, ASCEND) found no significant reduction in major cardiovascular events at ~1 g/day. The high-dose icosapent-ethyl trial REDUCE-IT showed a clear benefit in high-risk, statin-treated patients with elevated triglycerides, but the STRENGTH trial using a different high-dose EPA/DHA formulation found none — leaving genuine uncertainty about whether the REDUCE-IT result reflects EPA specifically or its mineral-oil comparator. Triglycerides: here the evidence is strong and consistent. Cognition/dementia and mood: signals are weak and inconsistent; supplementation is not established to prevent dementia or to treat depression in general populations. Inflammation: biomarkers often improve, but the clinical meaning of those changes is uncertain.

Protocol & dosing

For general intake, most guidelines point to eating oily fish a couple of times per week or a supplement providing roughly 250–500 mg combined EPA+DHA per day. For lowering elevated triglycerides, trials use much higher doses — typically 2–4 g/day of combined EPA+DHA, which is a therapeutic dose best taken under medical supervision.

• Form: triglyceride (TG) and re-esterified triglyceride (rTG) forms are generally better absorbed than the ethyl-ester (EE) form, though EE concentrates are well studied at high doses.
• With food: take with a fat-containing meal to improve absorption and reduce reflux/”fishy burps.”
• EPA:DHA ratio: no ratio is proven superior for general use; EPA-dominant products are favoured in the cardiovascular-risk context, DHA matters more where membrane/neural content is the goal.
• Label-reading: dose by actual EPA+DHA content, not total fish-oil weight — a “1000 mg fish oil” capsule may contain only ~300 mg EPA+DHA.

Risks & common myths

“It thins the blood dangerously”: high doses can modestly affect platelet function, but large trials have not shown a meaningful excess of serious bleeding at common doses; a small increase in atrial fibrillation has been seen at high (3–4 g) doses. “Fish oil does nothing”: an overstatement — the triglyceride effect is real and REDUCE-IT was positive — but so is the opposite claim, since STRENGTH, VITAL, and ASCEND were null for events. The careful reading is that benefit, if any, is concentrated in specific high-risk, high-triglyceride groups. Oxidation/rancidity: omega-3s oxidise easily; rancid product is a real quality issue, so favour fresh, properly stored, third-party-tested supplements. Mercury: purified fish-oil supplements are generally low in mercury and other contaminants, unlike some whole large predatory fish.

Who it’s for

Most useful for people with elevated triglycerides or low dietary fish intake, and reasonable as general nutritional insurance. People on anticoagulants, with atrial fibrillation, or planning surgery should consult a clinician before high-dose use.

Where to get it

If you choose to supplement, prioritise third-party-tested products with verified EPA/DHA content and low oxidation. You can find quality EPA/DHA fish oil on iHerb.

Sources

• Bhatt DL et al. Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia (REDUCE-IT). N Engl J Med 2019. PMID 30415628. DOI
• Nicholls SJ et al. Effect of High-Dose Omega-3 Fatty Acids vs Corn Oil on Major Adverse Cardiovascular Events (STRENGTH). JAMA 2020. PMID 33190147. DOI
• Manson JE et al. Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer (VITAL). N Engl J Med 2019. PMID 30415637. DOI
• ASCEND Study Collaborative Group. Effects of n-3 Fatty Acid Supplements in Diabetes Mellitus (ASCEND). N Engl J Med 2018. PMID 30146932. DOI
• Abdelhamid AS et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev 2020. PMID 32114706. DOI