What are omega-3 fatty acids — and why isn't diet enough?
Omega-3 fatty acids are a family of polyunsaturated fats that your body cannot produce on its own — they must come from food. The three most important are ALA (alpha-linolenic acid, from plants), EPA (eicosapentaenoic acid), and DHA (docosahexaenoic acid) — the latter two from marine sources, primarily fatty fish.
Here is the problem: your body can convert plant-based ALA into EPA and DHA, but the conversion rate is only 5 to 10% for EPA and 2 to 5% for DHA. This means that flaxseed and walnuts — often touted as omega-3 sources — deliver very little of the biologically active forms in practice. To get 1 gram of EPA+DHA from flaxseed, you would need to eat 10 to 20 tablespoons every day.
Over the past century, the Western diet's omega-6 to omega-3 ratio has shifted from roughly 2:1 to 15 to 20:1. Omega-6 (from sunflower, soybean, and corn oil in processed food) and omega-3 compete for the same enzyme pathways — and omega-6 produces pro-inflammatory signaling molecules, while omega-3 produces anti-inflammatory ones. A skewed ratio drives chronic low-grade inflammation — the foundation for cardiovascular disease, depression, joint problems, and neurodegeneration.
💡 Did you know? A single serving of salmon (about 5 oz) delivers 2 to 3 grams of EPA+DHA — more than most supplements provide per capsule. But only about 20% of adults eat fish two or more times a week. The omega-3 index test (the share of EPA+DHA in red blood cell membranes) shows that most people in the Western world fall below 6% — the optimal level is above 8%.
The heart and blood vessels — the strongest evidence
The cardiovascular effects of omega-3 fatty acids have been studied intensively for over 40 years. The starting point was the observation that Greenlandic Inuit — who ate enormous quantities of fish and seal — had extremely low rates of heart disease despite a high-fat diet.
The REDUCE-IT trial (Bhatt et al., NEJM, 2019 — 8,179 patients) produced the most striking results so far. High-dose purified EPA (4 grams of icosapent ethyl daily) reduced the risk of cardiovascular events by 25% in patients with elevated triglycerides — even though they were already on statins. The effect was larger than the triglyceride reduction alone could explain, suggesting that EPA's anti-inflammatory and plaque-stabilizing properties play a central role.
The mechanisms behind heart protection are numerous: EPA and DHA lower triglycerides (25 to 30% at 2 to 4 g/day), improve endothelial function (the inner lining of blood vessels), reduce platelet stickiness (clotting risk), lower blood pressure (2 to 4 mmHg systolic), and have anti-arrhythmic effects (stabilizing the heart's electrical signals).
The brain and depression — DHA's second home
The brain is roughly 60% fat, and DHA accounts for 40% of the polyunsaturated fatty acids in the cerebral cortex. It is not just filler — DHA is structurally embedded in the cell membranes of neurons, where it affects membrane fluidity, receptor density, and signal transmission. Without adequate DHA, synapses cannot function optimally.
The link between omega-3 and depression has been examined in numerous meta-analyses. The most cited (Liao et al., Translational Psychiatry, 2019 — 26 RCTs, 2,160 participants) found that omega-3 supplements had a significant antidepressant effect, with an effect size (SMD) of 0.28 — comparable to the early treatment response to SSRIs. The effect was most pronounced with EPA-dominant formulations (at least 60% EPA) and in clinical depression rather than subclinical symptoms.
The mechanisms are multifold: EPA reduces neuroinflammation (microglial cells in the brain are sensitive to omega-3 status), DHA supports serotonin transport by making cell membranes more fluid, and omega-3-derived neuroprotectins (NPD1) protect against neuronal cell death. Epidemiological studies also show that countries with higher fish consumption have lower rates of depression — Japan and Iceland have some of the lowest depression rates in the world.
Inflammation's firefighter — resolvins and protectins
For a long time, scientists believed that inflammation simply "burned out" on its own. The discovery of resolvins and protectins in the early 2000s — by Charles Serhan at Harvard — revolutionized our understanding. Inflammation is actively shut down by specialized lipid mediators produced from EPA and DHA.
Resolvin E1 (from EPA) and resolvin D1 (from DHA) signal neutrophils to stop migrating to the site of inflammation, stimulate macrophages to phagocytose (clean up) dead cells, and activate tissue repair. Without enough omega-3, too few resolvins are produced — and acute inflammation can transition into chronic low-grade inflammation ("inflammaging").
Protectin D1 (also known as neuroprotectin D1 in the brain) shields neurons from oxidative damage and inhibits apoptosis. Maresins (a third class of omega-3-derived mediators) accelerate wound healing and tissue regeneration. It is an entire anti-inflammatory signaling system that depends on the availability of omega-3.
🔬 The REDUCE-IT trial (NEJM, 2019) is the most high-profile omega-3 study in decades. Key finding: high-dose purified EPA reduced cardiovascular events by 25% — regardless of triglyceride level. This suggests that EPA's anti-inflammatory effect (via resolvins) is at least as important as the triglyceride reduction itself.
Dosing, sources, and quality
Practical guidance based on current research:
- Food sources — Fatty fish is the gold standard: salmon (1.5 to 3 g/serving), mackerel (1.8 to 2.6 g), herring (1.7 to 2 g), sardines (1.5 g), anchovies (1.4 g). Shellfish provides less. Plant-based ALA (flaxseed, chia seeds, walnuts) converts at only 5 to 10% efficiency.
- General dose (supplements) — 1 to 2 grams of EPA+DHA daily for most adults. For elevated triglycerides, a doctor may prescribe 2 to 4 grams. For depression: an EPA-dominant formula, at least 1 gram of EPA daily.
- Form — Triglyceride form (re-esterified) is absorbed 70% better than ethyl ester form (the most common in cheap supplements). Phospholipid form (krill oil) has high bioavailability but lower EPA+DHA content per capsule. Read the label — what counts is mg of EPA+DHA, not total fish oil.
- Timing — Take with a fat-containing meal — absorption increases 3x when taken with fat. Split the dose (morning + evening) at higher intakes to avoid fish burps.
- Quality — Oxidized (rancid) fish oil can be counterproductive. Check the TOTOX value (<26) or buy products certified by IFOS (International Fish Oil Standards). Refrigerate after opening. The smell test: if it smells strongly of fish, it is likely oxidized.
- Algae oil — A vegetarian alternative that delivers DHA (and often EPA) directly from algae — the same source fish originally get their omega-3 from. Equivalent in bioavailability, but more expensive per gram.
- Blood test — The omega-3 index measures the share of EPA+DHA in red blood cell membranes. Below 4% = high risk, 4 to 8% = suboptimal, above 8% = optimal. The test is available through some clinics and health labs.
Omega-3 myths
- "Flaxseed gives you enough omega-3" — Flaxseed provides ALA, not EPA or DHA. The conversion rate is 5 to 10% for EPA and 2 to 5% for DHA. You would need 10 to 20 tablespoons of flaxseed daily to match a single serving of salmon. Vegetarians should consider algae oil, not flaxseed.
- "All fish oil is the same" — The quality differences are enormous. Cheap ethyl ester forms are absorbed 30 to 50% less efficiently than triglyceride forms. Oxidized oil (high TOTOX) can actually promote inflammation. And the amount of EPA+DHA per capsule ranges from 250 mg to 1,000 mg — always read the label.
- "Omega-3 dangerously thins the blood" — At normal supplement doses (1 to 3 g), studies show no increased bleeding risk. Even at 4 g daily in REDUCE-IT, no serious bleeding events were observed. However, patients on blood thinners should consult their doctor at high doses (>3 g).
- "Krill oil is better than fish oil" — Krill oil has high bioavailability per gram, but typically contains only 200 to 300 mg of EPA+DHA per capsule (vs. 500 to 1,000 mg in quality fish oil). Per gram of EPA+DHA, krill oil is 3 to 5 times more expensive, with no proven clinical superiority.
- "Omega-3 doesn't make a difference" — Some large meta-analyses (Aung et al., JAMA Cardiology, 2018) found weak effects — but they included studies with low doses and short follow-up periods. More recent trials with adequate doses (2+ g) and longer follow-up (REDUCE-IT, VITAL) show clear benefits.
Cipoli analysis
Group comparison and patternsCipoli group comparison coming soon
In this section, we will compare Cipoli users who take omega-3 supplements with those who don't — and explore how it correlates with inflammation, mood, and cardiovascular health.
The analysis will include:
Why isn't the analysis available yet? To create meaningful group comparisons, we need enough anonymized responses from our users. The more people who map their health, the better and more reliable the analyses become.
Help us get there faster
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