A study published in Scientific Reports analysed 47 commercial omega 3 products in Spain and found that 80% exceeded international oxidation limits. What you buy as 'fish oil' may be closer to rancid oil than a functional food supplement.
Omega 3 fatty acids EPA and DHA are essential for cardiovascular health, cognitive function and inflammation control. But quality varies dramatically between brands. Most use low concentrations, processes that oxidise the oil and molecular forms your body barely absorbs.
In this guide you'll learn what differentiates EPA from DHA, how much you need according to your goals, how to verify it isn't oxidised and what to look for on the label to avoid wasting money. Without unnecessary jargon, just what works backed by research.
80% of commercial omega 3 products exceed oxidation limits, losing efficacy and generating inflammatory by-products
The essentials about omega 3 EPA and DHA
- EPA (eicosapentaenoic acid) acts mainly on inflammation and mood; DHA (docosahexaenoic acid) is structural for brain and retina.
- Optimal dosage: 1,000–2,000 mg EPA+DHA combined daily for healthy adults (not total omega 3, only EPA+DHA).
- Look for triglyceride or phospholipid form (not ethyl ester), IFOS or Friend of the Sea certification, and TOTOX value <10.
- The oil should smell of fresh sea, never rotten fish. If it smells bad, it's oxidised.
- Take it with meals containing fat for optimal absorption.
What are EPA and DHA: two omega 3s with different functions
When you talk about omega 3, you're talking about a family of polyunsaturated fatty acids. The three main ones are:
- ALA (alpha-linolenic acid): present in flaxseeds, chia, walnuts. Your body must convert it to EPA/DHA.
- EPA (eicosapentaenoic, 20 carbons): anti-inflammatory function, cardiovascular regulation, immune modulation.
- DHA (docosahexaenoic, 22 carbons): structural component of neuronal membranes, retina, spermatozoa.
The problem with plant ALA: conversion to EPA is 5–10% and to DHA less than 1% in most adults. If you rely only on plant sources, you'll hardly reach optimal levels.
EPA acts as a modulator: it reduces production of pro-inflammatory eicosanoids, competes with omega 6 (abundant in modern diet) and improves cell membrane fluidity. Meta-analyses show that high EPA doses (1,000–2,000 mg/day) reduce depressive symptoms comparable to some antidepressants in mild-to-moderate cases.
DHA is structural: it represents 40% of polyunsaturated fatty acids in the brain and 60% in the retina. Longitudinal studies associate high blood DHA levels with less cognitive decline and better executive function in those over 55.
How they work in your body: biological mechanisms
Once ingested, EPA and DHA incorporate into cell membranes in a process that takes 2–3 months to reach equilibrium (which is why serious studies last a minimum of 12 weeks).
Three main mechanisms:
- Inflammation modulation: EPA competes with arachidonic acid (omega 6) for the COX enzyme, generating series 3 prostaglandins (anti-inflammatory) instead of series 2 (pro-inflammatory). DHA produces resolvins and protectins, molecules that actively 'switch off' the inflammatory response.
- Membrane fluidity: both, being polyunsaturated, make membranes more flexible. This improves function of receptors (insulin, neurotransmitters), ion channels and cell communication.
- Gene regulation: they activate PPAR-α and PPAR-γ (nuclear receptors), modulating expression of genes related to lipid metabolism, glucose and adipogenesis. Hence their effect on triglycerides.
A Cochrane meta-analysis with 79 trials (>100,000 participants) showed that supplementation with EPA+DHA reduces triglycerides by 15–30% depending on dosage, with no adverse effect on LDL (unlike statins which sometimes raise it).
Benefits backed by research: what to expect (and what not)
Cardiovascular: solid evidence in triglyceride reduction (grade A). Moderate evidence in reducing cardiovascular events in people with prior history. The REDUCE-IT study (2019) with 4 g/day of purified EPA reduced major cardiovascular events by 25% in high-risk patients.
Brain and cognition: DHA improves verbal fluency and working memory in young adults with low baseline intake. In older people, results are mixed: prevention seems more effective than reversing established decline. A study in JAMA with >1,500 older adults found that high DHA levels were associated with 47% less risk of dementia.
Mood: meta-analysis of 26 trials shows that EPA >1,000 mg/day improves depressive symptoms (moderate effect size). DHA alone showed no effect. The EPA:DHA ratio seems to matter: ratios of 2:1 or 3:1 (more EPA) work better for depression.
Systemic inflammation: consistent reductions in CRP (C-reactive protein), IL-6 and TNF-α in studies with doses >2,000 mg/day for a minimum of 8 weeks.
Pregnancy: DHA is critical for fetal neurological development, especially in the third trimester. Recommendations: 200–300 mg/day DHA for pregnant women.
What it doesn't do: cure autoimmune diseases, eliminate joint pain (may reduce it in arthritis), reverse established Alzheimer's, substitute for statins in severe high cholesterol.
Recommended dosage: how much EPA and DHA you need
Common confusion: the label says "1,000 mg of fish oil", but contains only 300 mg of EPA+DHA. What matters is the milligrams of EPA and DHA, not the total oil.
Dosage by objective:
- General maintenance: 1,000–1,500 mg EPA+DHA/day (approximately 2 capsules of standard concentration).
- Cardiovascular health: 1,500–2,000 mg/day.
- Elevated triglycerides: 2,000–4,000 mg/day (under medical supervision >3,000 mg).
- Depression/mood: 1,000–2,000 mg EPA (with EPA:DHA ratio of 2:1 or higher).
- Pregnancy: 200–300 mg DHA/day minimum.
- Cognitive performance: 1,000 mg DHA/day.
Safe upper limit: 5,000 mg/day according to EFSA (European Food Safety Authority). Above that, theoretical risk of increased bleeding (though studies with 10 g/day showed no serious adverse effects).
Important note: if you take anticoagulants (warfarin, apixaban), consult your doctor before exceeding 1,000 mg/day, although clinical interactions are rare.
How to choose the best omega 3: what to look for on the label
This is where most people waste money. Five critical factors:
1. Molecular form: triglyceride > ethyl ester
Natural fish oil is in triglyceride (TG) form. To concentrate it, many brands convert it to ethyl ester (EE), a cheaper process but with 30–50% lower absorption.
The best brands re-esterify the EE back to reconstituted triglyceride (rTG), recovering bioavailability. There's also phospholipid form (from krill), with excellent absorption but more expensive.
How to identify it: if the label doesn't specify, it's probably EE. Look for "natural triglyceride", "rTG" or "phospholipid".
2. Concentration: minimum 60% EPA+DHA
Standard oil has 30% EPA+DHA (300 mg in a 1,000 mg capsule). Concentrates reach 70–85%. Higher concentration = fewer capsules = less potential oxidation.
3. Freshness: TOTOX value and expiry date
TOTOX (Total Oxidation Value) measures peroxides and aldehydes. International standard: <26. Quality products are <10.
Home test: prick a capsule and smell it. It should smell of fresh sea, never rotten fish. If it smells bad, it's oxidised (even if the date is valid).
4. Certifications: IFOS, Friend of the Sea, MSC
IFOS (International Fish Oil Standards) is the gold standard: it analyses purity, concentration, freshness and sustainability. Look for products with 5-star IFOS.
Other valid certifications: Friend of the Sea (sustainability + purity), MSC (sustainable fishing).
5. Origin and processing
Small fish (anchovies, sardines, mackerel) accumulate less mercury than tuna or salmon. Processing in oxygen-free environment (nitrogen) minimises oxidation.
Brand should specify molecular distillation to remove heavy metals, PCBs and dioxins.
The Longevitalis protocol: food supplements with clinical doses
At Longevitalis we've developed 3 complementary protocols formulated with clinical doses and only evidence-based ingredients:
- LongeviNocturno: designed for overnight repair with magnesium glycinate, L-theanine and extracts that improve deep sleep.
- Vitalis Renova+: morning formula for cellular renewal with NAD+ precursors, resveratrol and quercetin.
- LongeviSkin: beauty from within with marine collagen, hyaluronic acid and antioxidants.
All manufactured in Spain under GMP (Good Manufacturing Practices), with purity certification and complete transparency in formulation. If you're looking for an integrated protocol beyond omega 3, you can explore our formulas at longevitalis.com/products.
Side effects and contraindications
Omega 3 is generally safe, even at high doses. Most common adverse effects:
- Reflux, fish-flavoured burps: take with meals, freeze the capsules or switch to enteric form (coating resistant to gastric acid).
- Loose stools: occasional with doses >3,000 mg/day. Reduce dose or divide into several doses.
- Increased bleeding (theoretical): studies with 10 g/day showed no clinical effects. Caution if you take anticoagulants or pre-surgery (stop 1–2 weeks before).
Relative contraindications:
- Allergy to fish or shellfish (although purified oil rarely contains allergenic proteins, check).
- Severe hypotension (omega 3 may slightly reduce blood pressure).
Drug interactions: theoretically increases effect of anticoagulants and antiplatelet agents, though real clinical interactions are rare at doses <3,000 mg/day.
Pregnancy/breastfeeding: safe and recommended. Avoid fish liver oils (excess vitamin A). Opt for standard fish oil or krill.
Frequently asked questions about omega 3 EPA and DHA
Can I get enough omega 3 just from my diet?
Yes, if you eat 2–3 servings weekly of oily fish (salmon, mackerel, sardines, anchovies). A 100g serving of salmon provides ~2,000 mg EPA+DHA. But 80% of people in Spain don't reach that frequency, hence the value of supplementing. Plant sources (flax, chia) provide ALA, but conversion to EPA/DHA is <10%.
Is fish oil or krill oil better?
Krill has advantages: omega 3 in phospholipid form (better absorption), natural astaxanthin (antioxidant), less oxidation risk. Disadvantages: more expensive and lower concentration (you need more capsules). For most people, quality fish oil in rTG form is optimal for value for money.
How long does it take to work?
Cellular levels take 8–12 weeks to stabilise. For triglycerides, visible changes in blood tests at 4–6 weeks. For mood or cognition, a minimum of 8 weeks. The key is consistency: it's not an acute effect like caffeine.
Does omega 3 make you gain weight?
No. Although they're fats (9 kcal/g), typical doses provide only 10–20 kcal. Studies show that omega 3 improves body composition (more lean mass, less visceral fat) probably from metabolic effects, not calories.
Can I take omega 3 if I'm vegetarian/vegan?
Options: algae oil (contains EPA+DHA without fish, expensive but effective) or plant ALA + optimised conversion (reduce omega 6, ensure sufficient zinc/magnesium). Realistically, algae is the best option for vegans who want optimal levels.
Do I need to refrigerate the capsules?
Not essential if they're quality and in opaque blister with antioxidants (vitamin E). Yes recommended if you live in a hot climate or the packaging is clear plastic. Freezing them doesn't damage the oil and reduces burps.
Conclusion: invest in quality, not marketing
Omega 3 is one of the few food supplements with solid evidence across multiple systems: cardiovascular, brain, inflammation, mood. But only if you choose a product that isn't oxidised, with bioavailable form and clinical doses.
Most of the Spanish market falls short on at least two of those three criteria. Don't fall for generic "fish oil" from the supermarket: you're paying for oxidation.
Your checklist:
- Triglyceride form (natural or rTG) or phospholipid
- Minimum 60% EPA+DHA concentration
- TOTOX <10 or IFOS certification
- 1,000–2,000 mg EPA+DHA/day depending on goal
- Smell of fresh sea (home quality test)
If you want to explore the best supplements for longevity beyond omega 3, we have a complete guide. And if sleep is your priority, start with how to sleep better before adding supplements.
Intelligent supplementation starts with choosing well, not buying more.
Disclaimer: This information is for educational purposes and does not replace professional medical advice. Consult your doctor before starting any supplementation protocol, especially if you take anticoagulant medication or have pre-existing cardiovascular conditions. Food supplements should not be used as substitutes for a balanced diet and healthy lifestyle.
