In October 2026 the University of Southern California published the results of a two-year trial: older adults took 2,000 mg of DHA every day, yet after two years their memory was no better than in those who took a placebo. Does that mean fish oil can be crossed off the menu? No – but it is a good reason to look at what is actually known about omega-3, how much of it you need a day and how to compare the capsules on the shelf.
Contents
- What the new trial showed
- Omega-3, EPA, DHA and ALA: which is which
- What may be said about omega-3 in the EU
- Food first: how much fish a week
- How to choose omega-3 by the label
- A plant source: flaxseed oil
- Omega-3 in the Vitateka catalogue
- Safety: when to ask a doctor first
- Frequently asked questions
What the new trial showed
The study was run by researchers at the University of Southern California (USC) and published in the journal eBioMedicine; the press release came out on 22 October 2026 (the paper via DOI).
- Who took part: 365 people aged 55–80 who rarely eat fish and are at increased risk of Alzheimer's disease; almost half (47%) carry the APOE4 gene variant.
- What they took: 2,000 mg of DHA a day or a placebo for two years. The trial was double-blind: neither the participants nor the researchers knew who got what.
- What was measured: DHA in the cerebrospinal fluid, memory and thinking tests at the start and after two years, and the volume of the hippocampus – the part of the brain linked to memory.
- Result: after six months DHA in the cerebrospinal fluid was on average 17% higher – it did reach the brain. But after two years the DHA group scored no better on the tests than the placebo group, and the hippocampus shrank just the same.
The lead researcher, Hussein N. Yassine, says that on these results fish oil supplements cannot be seen as a way to stay clear of Alzheimer's disease. The authors suggest that omega-3 within a diet – for example a Mediterranean one, with fish, vegetables, pulses, nuts and olive oil – may work differently from a single capsule, and they are studying this further.
What the trial does not say. It does not mean that omega-3 is "useless": it tested one question – whether a high dose of DHA keeps memory intact in older people at risk. It draws no conclusions about the normal function of the brain, heart and vision, about diet in pregnancy or about eating fish.
Omega-3, EPA, DHA and ALA: which is which
Omega-3 is a group of polyunsaturated fatty acids. Three of them matter in the diet:
- ALA (alpha-linolenic acid) – the plant omega-3: flaxseed, rapeseed and hemp oil, walnuts, chia seeds.
- EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) – the "marine" omega-3: oily fish, seafood, fish oil, algal oil.
The body cannot make ALA itself, so it has to come from food. It can turn ALA into EPA and DHA only to a small extent – which is why fish and supplements are their main sources.
"Fish oil 1,000 mg" and "omega-3 1,000 mg" are not the same thing. The big number on the jar is often the amount of oil in a capsule, while the EPA and DHA in it range from 120 to 750 mg. Compare the sum of EPA + DHA per daily dose.
What may be said about omega-3 in the EU
In the EU the benefits of nutrients may only be described in the wording of the register of authorised claims (Regulation 432/2012). For omega-3 these are:
- EPA and DHA contribute to the normal function of the heart.
- DHA contributes to maintenance of normal brain function.
- DHA contributes to the maintenance of normal vision.
- ALA contributes to the maintenance of normal blood cholesterol levels.
Conditions: for the heart, 250 mg of EPA and DHA a day; for the brain and vision, 250 mg of DHA a day; for cholesterol, 2 g of ALA a day. There are also claims about triglycerides and blood pressure, but they refer to 2–3 g of EPA and DHA a day; in total no more than 5 g of EPA and DHA a day should come from supplements.
An important difference. The brain claim is about normal brain function at 250 mg of DHA a day. It is not a promise to keep your memory as you age – and the USC trial showed that even 2,000 mg of DHA a day did not give such a result in people at risk.
Food first: how much fish a week
EFSA has set an adequate intake of 250 mg of EPA and DHA a day for adults – about 1.75 g a week. That usually means one or two portions of oily fish a week. How much fish gives this amount, according to the Norwegian food composition table Matvaretabellen (raw fish):
| Fish | EPA + DHA per 100 g | Amount a week for ~1.75 g |
|---|---|---|
| Mackerel caught August to December | 4.5 g | ≈ 40 g |
| Sprat | 2.6 g | ≈ 70 g |
| Rainbow trout, farmed | 1.8 g | ≈ 100 g |
| Herring | 1.7 g | ≈ 105 g |
| Salmon, wild / farmed | 1.4 / 1.2 g | ≈ 130 / 150 g |
| Cod | 0.2 g | ≈ 760 g |
| Tuna canned in water | 0.2 g | ≈ 830 g |
How oily a fish is depends on the season: mackerel caught from February to June has only 0.65 g of EPA and DHA per 100 g in the same table. Lean fish – cod, saithe, pike – gives little omega-3.
A supplement makes sense if fish is on your plate less than once a week. The same order – plate first, capsule second – is stressed by the authors of the USC trial too.
How to choose omega-3 by the label
- Count EPA + DHA per daily dose. A capsule of ICONFIT Premium Omega-3 has 500 mg of EPA and 250 mg of DHA, a capsule of Herbin Mega Omega-3 180 and 120 mg. One capsule of either is enough for 250 mg of EPA and DHA a day.
- Check how many capsules make a daily dose. For VITATEKA Omega-3 Forte 1000 mg the daily dose is 2 capsules: 360 mg of EPA and 240 mg of DHA. For Oleofarm Omega 3-Vitum forte it is 1–2 capsules, each with 363 mg of EPA and 242 mg of DHA.
- "Omega-3-6-9" complexes contain little EPA and DHA. Most of them is plant oil – flaxseed and sunflower. OstroVit Omega 3-6-9 has 72 mg of EPA and 48 mg of DHA in a daily serving of three capsules, VitalHarmony Omega 3-6-9 the same in one capsule. Most people already get plenty of omega-6 from food.
- Cod liver oil also means vitamins A and D. A capsule of OstroVit cod liver oil has 215 µg of vitamin A (27% NRV) and 3 µg of vitamin D; according to the label it is not suitable for children or pregnant and breastfeeding women. If you take vitamin A or D separately, add up the doses.
- Price per day and price of omega-3. Prices on 26.10.2026 (delivery to Estonia, VAT included): ICONFIT Premium, 90 capsules, €20.89 – about €0.23 a day for 750 mg of EPA and DHA; Herbin Mega Omega-3, 90 capsules, €12.50 – about €0.14 a day for 300 mg. Per 1,000 mg of EPA and DHA the first one is cheaper: about €0.31 against €0.46.
- Freshness and storage. Fish oil oxidises in light and heat: keep the jar closed in a cool place and watch the best-before date. The vitamin E in many capsules is an antioxidant for the oil itself.
A plant source: flaxseed oil
Unrefined VITATEKA flaxseed oil contains 58.9 g of ALA per 100 g. The cholesterol claim needs 2 g of ALA a day – about 3.5 g of oil, less than a teaspoon. It is added to salads, porridge and chilled dishes; it is not for frying, and an opened bottle is kept in the fridge and used within a month.
ALA does not replace EPA and DHA: if there is little fish in your diet, flaxseed oil will not fill that gap.
Omega-3 in the Vitateka catalogue
Everything below is in stock on 26.10.2026; the EPA and DHA amounts are taken from the labels on our website. More options are in the Omega-3 and fatty acids section, plant oils in Edible oils.
- 750 mg of EPA + DHA in 1 capsule: ICONFIT Premium Omega-3, 90 capsules.
- 605 mg in 1 capsule: Oleofarm Omega 3-Vitum forte, 60 capsules; daily dose 1–2 capsules.
- 600 mg in 2 capsules: VITATEKA Omega-3 Forte 1000 mg, 90 capsules; a smaller pack is VITATEKA Omega-3 1000 mg, 30 capsules (1–2 capsules: 300–600 mg).
- 300 mg in 1 capsule: Herbin Mega Omega-3, 90 capsules; OstroVit Omega 3, 90 capsules – 300 mg per serving (1,000 mg of fish oil).
- Plant ALA: VITATEKA flaxseed oil, 250 ml.
Safety: when to ask a doctor first
- Upper limit. According to EFSA (2012), up to 5 g of EPA and DHA a day from supplements raises no safety concerns in adults. That is far more than the doses on the labels – take no more than the manufacturer's daily dose.
- Blood-thinning medicines. If you take anticoagulants or antiplatelet medicines, discuss fish oil with your doctor; before surgery tell the doctor that you take it.
- Pregnancy and breastfeeding. Ask a doctor before taking any supplement; do not take cod liver oil without their approval because of the vitamin A.
- Fish allergy. Fish oil is a fish product; most capsule shells are made of gelatine.
In short
- In older people at risk, 2,000 mg of DHA a day for two years gave no advantage for memory compared with a placebo.
- In the EU one may speak about normal function of the heart (250 mg of EPA and DHA), brain and vision (250 mg of DHA) – only in these wordings.
- 250 mg of EPA and DHA a day equals one or two portions of oily fish a week.
- With a supplement, compare the sum of EPA + DHA in the daily dose and its price, not "1,000 mg of fish oil".
- 3-6-9 complexes and flaxseed oil give mainly plant fats, not EPA and DHA.
- In pregnancy, while breastfeeding and when taking medicines – see a doctor first.
Frequently asked questions
Is it worth taking fish oil for memory?
The claim allowed in the EU reads: "DHA contributes to maintenance of normal brain function" – at 250 mg of DHA a day. Fish oil makes no promise about memory in old age: in the USC trial 2,000 mg of DHA a day for two years made no difference compared with a placebo in people aged 55–80 at risk.
How much omega-3 a day?
For adults EFSA has set an adequate intake of 250 mg of EPA and DHA a day. The heart, brain and vision claims refer to 250 mg a day, and in total no more than 5 g of EPA and DHA a day from supplements. Take the dose on the label.
What is the difference between fish oil and omega-3?
Fish oil is the oil from fish, and EPA and DHA are part of it. A capsule with 1,000 mg of fish oil usually holds 300–750 mg of EPA and DHA; that figure is given in the composition table.
Can flaxseed oil replace fish oil?
Flaxseed oil is a source of ALA, the plant omega-3: 2 g of ALA a day is about 3.5 g of oil. But the body turns only a small share of ALA into EPA and DHA, so flaxseed oil will not fully replace fish or fish oil.
When is the best time to take fish oil?
With a meal – that is what most manufacturers write on their labels, for example Oleofarm and VITATEKA. The time of day does not matter; what matters more is taking it regularly and not exceeding the dose on the pack.
Can pregnant women take fish oil?
Only after consulting a doctor. Do not take cod liver oil without their approval: it contains vitamin A, and the OstroVit label, for example, states that it is not suitable for pregnant and breastfeeding women.
Important information
A food supplement is not a medicine and does not replace a varied, balanced diet and a healthy lifestyle. Do not exceed the recommended daily dose. If you are pregnant, breastfeeding, taking medicines or under medical supervision, consult a doctor before use. Keep out of reach of children.
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