Omega-3

Yes — and this is the single biggest quality lever after IFOS certification. Ethyl ester (EE) is the cheaper, synthetic form most generic fish oil ships in; absorption studies (Dyerberg 2010, Schuchardt 2011) show 30-50% lower bioavailability vs the natural triglyceride (TG) or re-esterified triglyceride (rTG) forms. EE also oxidises faster and produces the classic 'fishy burp' that drives most users to quit. If a fish oil bottle doesn't say 'triglyceride form' or 'rTG' on the panel, assume it's ethyl ester. Pay the extra $5-10/month for the TG form — it's the difference between a clinical dose at 2 g/day vs needing 3 g/day to hit the same blood level.

Default to IFOS-certified fish oil in triglyceride form for the best $/gram of clinical-dose EPA+DHA. Krill oil delivers omega-3 bound to phospholipids (modestly better absorption per mg) plus a small dose of astaxanthin (antioxidant) — but krill caps typically contain only 50-150 mg combined EPA+DHA each, so reaching clinical dose costs 2-3x more per month. Algae oil is the right choice for vegetarians/vegans, anyone with fish allergies, and people prioritising the cleanest possible source (zero ocean-pollutant exposure) — it costs ~$40-60/month for the clinical dose but the EPA+DHA is identical to fish-source. Krill is mostly status-tier marketing; fish (IFOS, TG form) is the volume play that the trial literature actually used.

Depends on the goal. For mood and depression, the meta-analyses (Sublette 2011, Martins 2009) converge on EPA-dominant formulations with EPA:DHA ratio of 2:1 or higher — EPA appears to drive the antidepressant effect, DHA does not. For cardiovascular outcomes (REDUCE-IT) and triglyceride reduction, pure EPA (icosapent ethyl) is the prescription-grade formulation. For cognitive preservation and pregnancy, DHA-dominant formulations are appropriate — DHA is the brain's structural fatty acid. For general health / Omega-3 Index correction, a balanced formulation (EPA:DHA 1:1 or 1.5:1) is the default. Most general-purpose IFOS fish oils land at ~EPA:DHA 1.5:1, which is fine for baseline supplementation; only optimise the ratio if you're solving a specific endpoint.

General health / Omega-3 Index correction: 1-2 g/day combined EPA+DHA, indefinitely. Triglyceride reduction or cardiovascular risk: 2-4 g/day combined, sustained — the REDUCE-IT protocol used 4 g/day of pure EPA (icosapent ethyl). Mood / depression complement: 1-2 g/day with EPA:DHA ratio of 2:1 or higher. ADHD: 1-2 g/day, EPA-dominant, in children + adolescents per Bloch 2011. Cognitive preservation (older adults): 900 mg-2 g/day DHA-dominant, per Yurko-Mauro 2010. Note that 'fish oil 1000 mg' on the bottle label typically delivers only ~300-400 mg combined EPA+DHA — read the actives panel, not the gross oil weight.

IFOS (International Fish Oil Standards) is the gold-standard third-party testing program for omega-3 supplements. Every batch tested gets a public, batch-specific report showing: actual EPA + DHA content (vs label claim), TOTOX oxidation score, heavy metals (mercury, lead, cadmium, arsenic), PCB and dioxin levels, and a 1-5 star overall rating. The unregulated fish oil market is full of products that fail one or more of these — under-dosed actives, oxidised oil (TOTOX >26), or measurable heavy metals. Looking up your bottle's batch on the IFOS site (ifosprogram.com) takes 30 seconds and is the single best quality assurance step. Friend of the Sea and GOED are decent alternatives but less granular.

Often, yes. Fresh, high-quality omega-3 in triglyceride form barely smells fishy — there should be at most a faint marine note. Aggressive fishy taste or persistent fishy burps after dosing are usually a sign of one of three things: (1) ethyl ester form rather than triglyceride, (2) oxidised oil from poor storage or aged stock, or (3) excessive single-dose taken on an empty stomach. Fix: switch to TG-form IFOS-certified product, store the bottle refrigerated after opening, take with a meal containing fat, and split larger doses across two meals. If a fresh bottle smells aggressively rancid on day one, return it — that batch failed quality control.

Less than you'd think — IF you buy certified product. The ocean-pollutant load in fish increases up the food chain: small fish (anchovies, sardines, mackerel) accumulate far less mercury, PCBs, and dioxins than large predators (tuna, swordfish, shark). Reputable fish oil brands source from small-fish stocks and run molecular distillation that removes residual heavy metals to well below FDA limits. IFOS-certified product publishes the exact heavy-metal content per batch — typically 10-100x below regulatory thresholds. Algae oil sidesteps the question entirely (zero marine pollutant exposure). The mercury concern is real for cheap, uncertified, unsourced fish oil; it's effectively eliminated by buying IFOS-certified product.

Yes, if you genuinely eat fatty fish 2-3 servings per week, every week — salmon, sardines, mackerel, anchovies, herring deliver 1-2 g of combined EPA+DHA per serving. Reality check: most adults in the US, UK, and Europe average less than 1 serving per week, which lands the Omega-3 Index in the 4-5% range vs the 8%+ target associated with the lowest cardiovascular event rates. Plant sources (flax, chia, walnuts) are NOT a substitute — they deliver ALA, which converts to EPA at ~5% efficiency and to DHA at <0.5%. If you can sustain 3+ weekly servings of fatty fish, skip the supplement. If you can't (most people), the 1-2 g/day capsule is the simplest fix.