Key points
In short: Omega-3 fatty acids are essential, meaning the body cannot make them and they must come from diet or supplements. There are three main types: EPA and DHA, found mainly in oily fish, and ALA from plant sources such as flaxseed. The body converts ALA to EPA and DHA only inefficiently, which is why the marine forms are treated separately. NHS guidance is to eat at least two portions of fish a week, one of them oily.
- EPA and DHA: contribute to the normal function of the heart, with the beneficial effect obtained at a daily intake of 250mg of EPA and DHA combined.
- DHA specifically: contributes to the maintenance of normal brain function and to the maintenance of normal vision, each at a daily intake of 250mg.
- During pregnancy and breastfeeding: maternal intake of DHA contributes to the normal brain and eye development of the foetus and breastfed infants. The effect is obtained at 200mg of DHA daily in addition to the 250mg recommended for adults.
- ALA: contributes to the maintenance of normal blood cholesterol levels, at a daily intake of 2g.
- What to look for in a fish oil: the EPA and DHA figures rather than the total oil weight, the fish species used, whether the oil comes from flesh or liver, and whether batches are tested for oxidation.
- Flesh versus liver oil: oils from fish flesh differ from liver oils such as cod liver oil, which also contain vitamin A. That matters in pregnancy, where high vitamin A intake is not advised.
- Metabolics Omega 3 specifics: 550mg of EPA and DHA per capsule, extracted from anchovy, sardine and mackerel flesh, with added vitamin E and batch testing for oxidation.
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Worth checking first: anyone taking anticoagulant medication should speak to their GP or pharmacist before starting a fish oil.
Omega-3 is one of the most talked-about nutrients, and one of the most misunderstood. The term covers three different fatty acids, the amounts on supplement labels are not always comparable, and the guidance on how much you need is more specific than many people realise. This article explains what each type of omega-3 is, how much you need each day, where to find it in food, and what to look for if you choose a supplement.
What is omega-3?
Omega-3s are essential fatty acids, which means the body cannot produce them and they must come from diet or supplements. There are three main types:
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the long-chain, or marine, forms. They are found mainly in oily fish and seafood, and in algae, which is where fish obtain them in the first place.
ALA (alpha-linolenic acid) is the plant form, found in foods such as flaxseed, chia seeds and walnuts. The body can convert some ALA into EPA and DHA, but only in small amounts, so ALA is not treated as a substitute for the marine forms.
How much omega-3 do you need?
NHS guidance is to eat at least two portions of fish a week, one of which should be oily. A portion is around 140g.
For supplements, the figures that matter are the amounts of EPA and DHA, not the total weight of the oil. A 1,000mg fish oil capsule might contain anywhere from around 300mg to more than 600mg of EPA and DHA combined, depending on how concentrated the oil is.
The daily intakes linked to the authorised health claims are:
- EPA and DHA combined, 250mg a day: EPA and DHA contribute to the normal function of the heart.
- DHA, 250mg a day: DHA contributes to the maintenance of normal brain function and the maintenance of normal vision.
- DHA in pregnancy and breastfeeding, an additional 200mg a day on top of the 250mg for adults: maternal intake of DHA contributes to the normal brain and eye development of the foetus and breastfed infants.
- ALA, 2g a day: ALA contributes to the maintenance of normal blood cholesterol levels.
The best food sources of omega-3
EPA and DHA come mainly from oily fish:
- Salmon
- Mackerel
- Sardines
- Herring
- Trout
- Anchovies
White fish such as cod and haddock contain much smaller amounts. NHS guidance advises pregnant women, and women who may become pregnant, to eat no more than two portions of oily fish a week.
ALA comes from plant foods, including:
- Flaxseed (linseed) and flaxseed oil
- Chia seeds
- Hemp seeds
- Walnuts
- Rapeseed oil
For people who eat no fish, algal oil supplements are a plant-based source of EPA and DHA.
Fish oil or cod liver oil: what is the difference?
Fish oils are extracted either from the flesh of the fish or from the liver. Flesh oils, typically from small oily fish such as anchovy, sardine and mackerel, provide EPA and DHA. Liver oils such as cod liver oil also provide EPA and DHA, but contain vitamin A and vitamin D as well.
The vitamin A content is the important difference. NHS guidance advises against liver and liver products, including cod liver oil, during pregnancy, because high intakes of vitamin A can harm a developing baby. Anyone taking more than one supplement should also check their total vitamin A intake.
Choosing an omega-3 supplement
If you eat oily fish regularly you may already be meeting the guidance. If you rarely eat it, a supplement is one way to make up the difference. When comparing products, look for:
- The EPA and DHA content per capsule, not the total oil weight.
- The fish species, and whether the oil comes from the flesh or the liver.
- Oxidation testing. Omega-3 oils are prone to oxidation, so batch testing for freshness is a good sign of quality.
- Added vitamin E, which is commonly included to protect the oil from oxidation.
Our high-strength omega-3 fish oil capsules provide 550mg of EPA and DHA per capsule. The oil is extracted from the flesh of anchovy, sardine and mackerel, with added vitamin E, and every batch is tested for oxidation.
How to take omega-3
Omega-3 is fat-soluble, so it is best taken with a meal that contains some fat. The time of day matters less than taking it consistently, so choose a meal that fits your routine. If you find fish oil causes repeating, taking it with your largest meal of the day can help.
Who should check before taking omega-3?
- Anticoagulant or antiplatelet medication: anyone taking these should speak to their GP or pharmacist before starting a fish oil supplement.
- Pregnancy and breastfeeding: choose a flesh oil rather than a liver oil, and avoid supplements containing vitamin A unless advised otherwise.
- Upcoming surgery: mention any fish oil supplement to your healthcare team beforehand.
Quick FAQs
Do I need omega-3 if I eat fish?
If you eat at least two portions of fish a week, including one oily, you are meeting NHS guidance. A supplement can be useful if you rarely eat oily fish.
Is plant omega-3 as good as fish omega-3?
Plant foods provide ALA, which has its own role, but the body converts only small amounts into EPA and DHA. If you eat no fish, algal oil is a plant-based source of EPA and DHA.
Can I take omega-3 with my multivitamin?
Yes, omega-3 can be taken alongside most daily supplements. If your multivitamin contains vitamin A and you are pregnant, check the total amount you are taking.
Is cod liver oil the same as fish oil?
No. Cod liver oil comes from the liver and contains vitamin A and vitamin D as well as omega-3. Fish oils from the flesh of the fish provide EPA and DHA without the vitamin A.
Summary
Omega-3 covers three fatty acids: EPA and DHA from oily fish and algae, and ALA from plant foods. The amounts that matter are the EPA and DHA figures, with 250mg a day of EPA and DHA combined linked to the authorised heart claim. Two portions of fish a week, one of them oily, meets NHS guidance, and a flesh-derived fish oil is a straightforward option for anyone who eats little oily fish.
