Omega-3 (EPA/DHA) Supplement

## What it is Eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) are long-chain omega-3 polyunsaturated fatty acids found in cold-water fish, algae, krill, and certain seeds in trace amounts. The body can convert alpha-linolenic acid (ALA) from plant sources into EPA and DHA, but the conversion efficiency is low (5 to 10% to EPA, less than 1% to DHA in most adults). For practical purposes, meaningful EPA and DHA intake comes from fatty fish (salmon, mackerel, sardines, anchovies, herring) or supplements. The modern interest in marine omega-3s traces to the 1970s observation by Bang and Dyerberg that Greenland Inuit had unusually low rates of cardiovascular disease despite a high-fat diet, with the protective factor eventually attributed to high EPA and DHA intake from marine mammals. The intervening five decades produced the largest evidence base for any supplement in human history, with mixed but ultimately positive conclusions on cardiovascular hard endpoints when EPA-dominant formulations are used at 2 to 4 g/day. Legally most fish oil is a dietary supplement, but several formulations have prescription drug status: icosapent ethyl (Vascepa, ethyl ester EPA only, 4 g/day) and omega-3 acid ethyl esters (Lovaza, EPA + DHA mixed) are FDA approved as prescription medications for severe hypertriglyceridemia. The prescription forms have higher purity standards and often higher EPA/DHA concentrations, but the active species are the same as in supplements. WADA does not list omega-3s. The supplement market sells fish oil in three primary forms: triglyceride (TG, the natural form, used in most premium products), ethyl ester (EE, the form created during molecular distillation, used in budget products and prescription Lovaza), and re-esterified triglyceride (rTG, EE converted back to TG, used in mid-tier products). Bioavailability differs: rTG and TG forms are roughly 70% better absorbed than EE forms when taken with a low-fat meal, but the difference shrinks substantially when taken with a higher-fat meal. ## Mechanism of action EPA and DHA exert effects through multiple distinct mechanisms, which is why the literature spans cardiovascular, neurological, immune, and metabolic outcomes. The most-cited cardiovascular mechanism is competitive substitution of arachidonic acid in cell membrane phospholipids, which shifts eicosanoid production toward less-inflammatory and less-thrombotic 3-series prostaglandins and 5-series leukotrienes. This produces reductions in platelet aggregation, vasoconstriction, and inflammatory cytokine release. EPA at high doses (2 to 4 g/day) reduces hepatic VLDL production and triglyceride synthesis through PPAR-alpha activation and SREBP-1c suppression. The triglyceride-lowering effect is the most robust and dose-dependent of all omega-3 effects, with 20 to 50% reductions at 4 g/day in hypertriglyceridemic patients. EPA also has direct anti-inflammatory effects through resolvins and protectins (specialized pro-resolving mediators), which are bioactive metabolites that actively terminate inflammation rather than merely reducing it. DHA is the structural omega-3, accounting for roughly 25% of total brain phospholipid fatty acids and substantially more in retinal photoreceptors. DHA modulates synaptic membrane fluidity, neurotransmitter receptor function, and neuronal survival. Most cognitive and visual development effects are attributable to DHA rather than EPA. The pharmacokinetic profile is favorable. Plasma EPA and DHA rise within hours of dosing, but tissue incorporation (which is the relevant exposure for most outcomes) takes 6 to 12 weeks of consistent dosing to plateau. The omega-3 index (RBC EPA + DHA as a percentage of total fatty acids) is the most validated biomarker, with target values of 8% or higher for cardiovascular protection and typical Western baselines of 4 to 5%. ## Evidence base by outcome ### Triglycerides The most robust outcome. EPA + DHA at 2 to 4 g/day reduces fasting triglycerides by 20 to 50% in hypertriglyceridemic patients across more than 50 trials. Effect size scales with baseline triglycerides; patients above 500 mg/dL see the largest reductions. The Skulas-Ray 2019 AHA Science Advisory is the standard reference and supports prescription-dose omega-3s as adjunctive therapy for severe hypertriglyceridemia. ### Cardiovascular hard endpoints The REDUCE-IT trial (Bhatt 2019, n=8,179) randomized statin-treated adults with elevated triglycerides and high cardiovascular risk to icosapent ethyl 4 g/day or mineral oil placebo for a median 4.9 years. Primary composite endpoint (CV death, MI, stroke, coronary revascularization, unstable angina) was reduced 25% (HR 0.75). Cardiovascular death was reduced 20%. The effect is large enough that icosapent ethyl is now incorporated into AHA secondary prevention guidelines. The earlier JELIS trial (Yokoyama 2007, n=18,645 Japanese adults, EPA 1.8 g/day + statin) showed a 19% reduction in major coronary events. The parallel STRENGTH trial (Nicholls 2020, n=13,078, EPA + DHA carboxylic acid 4 g/day vs corn oil placebo) was negative for the same composite endpoint, which produced substantial discussion of whether the difference was due to EPA-only formulation, the mineral oil placebo (which may have been mildly harmful), or chance. The current consensus interpretation is that EPA-dominant high-dose formulations have hard-endpoint benefit in high-risk statin-treated populations. The lower-dose VITAL trial (n=25,871, 1 g/day EPA + DHA, primary prevention) was largely negative, indicating that the cardiovascular benefit is concentrated at higher doses in higher-risk populations. ### All-cause mortality The 2017 Bernasconi meta-analysis pooled 17 RCTs and reported a 7% reduction in cardiovascular mortality and a 10% reduction in MI risk with marine omega-3 supplementation. Effect sizes are smaller than statins but comparable to many cardiovascular interventions in absolute terms. ### Depression and mood The Mocking 2016 meta-analysis (13 RCTs in MDD) reported a moderate antidepressant effect (SMD = 0.40) for omega-3 supplementation, with the largest effects in EPA-dominant formulations and in adjunctive use with SSRIs. The 2019 Liao meta-analysis (26 RCTs) reached similar conclusions and recommended EPA-dominant formulations at 1 to 2 g/day for major depression. B-tier; reasonable adjunct. ### Cognitive decline The omega-3 cognitive evidence is mixed. Older adults with low baseline omega-3 status appear to benefit, while replete adults show minimal effects. The DHA-rich formulations are theoretically preferred for cognitive outcomes given DHA's role in neuronal membranes, but trial data have not consistently favored DHA-only over EPA + DHA. Treat omega-3 cognitive effects as small and population-dependent. ### Pregnancy and infant development DHA supplementation during pregnancy at 200 to 600 mg/day produces small improvements in infant visual acuity and cognitive development. The professional society recommendation is 200 mg DHA per day for pregnant and lactating women, achievable through 1 to 2 servings of low-mercury fatty fish per week or supplementation. ## Dosage and protocols The most-studied dose ranges: - General health and prevention: 1 g/day combined EPA + DHA (typical fish oil supplement at 1 capsule) - Triglyceride reduction: 2 to 4 g/day combined EPA + DHA - Cardiovascular secondary prevention with elevated triglycerides: 4 g/day icosapent ethyl (prescription) or equivalent EPA-dominant formulation - Major depression adjunct: 1 to 2 g/day EPA-dominant - Pregnancy: 200 to 600 mg/day DHA Read labels carefully. A '1,000 mg fish oil' capsule typically contains 300 mg of combined EPA + DHA, with the rest being filler oils. Premium concentrated formulations deliver 700 to 900 mg EPA + DHA per 1,000 mg capsule. Take with food, ideally a meal containing some fat. Absorption is substantially better in the fed state, and the GI side effects (fishy burps, mild reflux) are reduced with food. No cycling is required. Continuous daily use is the standard. Tissue omega-3 index plateaus at 8 to 12 weeks of consistent dosing and decays slowly over months after discontinuation. ## Side effects and safety GI side effects (fishy aftertaste, eructation, mild dyspepsia) affect 15 to 30% of users at 2 g/day or above. Enteric-coated capsules and dosing with food substantially reduce both. Freezer storage of capsules also helps because it slows the dissolution to past the stomach. Bleeding risk at high doses is real but usually overstated. The REDUCE-IT trial showed a small increase in major bleeding (2.7% vs 2.1%) and atrial fibrillation (5.3% vs 3.9%) at 4 g/day icosapent ethyl. The risk is meaningful in patients on dual antiplatelet therapy or anticoagulants and warrants clinician discussion. Discontinuing 5 to 7 days before elective surgery is the conventional precaution. The atrial fibrillation signal is a recently emphasized concern. Multiple trials at 4 g/day have shown roughly 30 to 50% increases in incident AF, with the absolute risk highest in older adults with pre-existing cardiovascular disease. Patients with paroxysmal AF should discuss high-dose omega-3 use with their cardiologist. Mercury and contaminant burden in fish oil is a public concern but is small in well-purified products. Molecular distillation removes essentially all mercury, PCBs, and dioxins. Look for IFOS (International Fish Oil Standards) certification or equivalent third-party testing for contaminant levels. Fish allergy is a contraindication for fish-derived omega-3s. Algal omega-3 supplements (DHA-dominant, with smaller amounts of EPA) are the alternative for vegan and fish-allergic users. Drug interactions are limited. Additive antiplatelet effects with aspirin, NSAIDs, warfarin, and DOACs are clinically meaningful at 2 g/day or above. Statin-omega-3 combinations are well-studied and complementary rather than interactive. ## Stack interactions and timing Omega-3s pair naturally with vitamin D, magnesium, and CoQ10 in a longevity-baseline stack. The combination with statins is particularly well-studied; omega-3s do not affect statin pharmacokinetics and the cardiovascular endpoints in REDUCE-IT were measured on top of statin therapy. Curcumin and high-dose omega-3 have additive antiplatelet effects, which is therapeutically useful in some inflammatory contexts but raises bleeding risk. Avoid combining at high doses if on anticoagulants without clinician input. Timing within the day is largely flexible. Once-daily evening dosing with dinner is the most common pattern. Splitting across breakfast and dinner improves GI tolerance at high doses. ## Practical notes Freshness is the most important quality variable. Rancid fish oil is unpleasant to consume, less effective, and theoretically harmful through oxidized lipid metabolites. Test by piercing a capsule and smelling: fresh fish oil smells mild and oceanic, rancid oil smells strongly fishy or paint-like. Sniff the capsules at the bottle opening; rancid product is detectable within seconds. The IFOS rancidity standards (peroxide value, anisidine value, totox) are the gold standard. Cost varies enormously. Budget fish oil runs 5 to 10 cents per gram of EPA + DHA; premium triglyceride or rTG products run 20 to 50 cents per gram. Prescription icosapent ethyl runs 5 to 10 dollars per day at retail without insurance. The supplement-prescription gap on cardiovascular outcomes is partly real (formulation matters) and partly a function of dose and indication. Storage matters. Refrigerate after opening. Keep away from light. Most premium brands have nitrogen-flushed bottles to slow oxidation. Cheap tablet-form fish oil tends to oxidize faster than capsules. Expect tissue omega-3 status (omega-3 index, if measured) to rise over 8 to 12 weeks. Triglyceride effects appear within 4 weeks. Mood effects in depression typically manifest by week 6 to 8. Cardiovascular hard-endpoint benefits in trials emerge over years rather than months.