You can eat
- Small and medium-sized oily fish: sardines, anchovies, mackerel and horse mackerel provide EPA and DHA and contain little mercury. Eat at least three servings of fish a week and prioritise oily fish [3].
- Salmon and trout: good sources of EPA and DHA, whether fresh or frozen.
- Seafood and shellfish: mussels, cockles, clams and prawns provide moderate amounts of EPA and DHA.
- Raw or unsalted roasted walnuts: the everyday nut with the most ALA. From the start of complementary feeding, offer them ground or as a paste. Do not give whole nuts to children under 5.
- Flax (linseed) and chia seeds, ground or crushed just before use to make their ALA available.
- Flaxseed or walnut oil, used uncooked in dressings. Extra virgin olive oil remains the everyday choice, although it provides little omega-3.
- Whole soya beans, edamame and tofu: small amounts of ALA as part of a plant-based diet.
- Purslane and leafy green vegetables: low in ALA, but they contribute to a varied eating pattern.
What to avoid
- Swordfish, bluefin tuna, shark (dogfish, porbeagle, spurdog, small-spotted catshark and blue shark) and pike: avoid these because of their mercury content if you are pregnant, could become pregnant or are breastfeeding. Children up to the age of 10 should avoid them too.
- Whole flax or chia seeds: much of the seed passes through undigested, so you do not benefit from its omega-3.
- Flaxseed oil for frying or high-heat cooking: it oxidises easily when heated.
- Taking omega-3 supplements without advice, especially if you take anticoagulants or antiplatelet medicines: speak to your doctor first.
- Pastries, snacks and industrially fried foods as your regular source of fat: they displace fish, nuts and extra virgin olive oil.
- Ultra-processed foods marketed as containing added omega-3: biscuits or pastries still provide refined flours and sugars.
- Tinned fish in refined oils: choose fish in its own juices or extra virgin olive oil instead.
Changes that help
Large predatory fish
Swordfish or bluefin tuna → sardines, mackerel or fresh salmon baked in the oven, to get EPA and DHA without accumulating mercury
Whole seeds in yoghurt
Whole flax or chia seeds → freshly ground or crushed seeds, so your body can access their ALA fats
Afternoon snack
Biscuits or bars marketed as containing omega-3 → a handful of 25–30 g of raw walnuts with a whole piece of fresh fruit
Everyday tinned fish
Tuna tinned in refined sunflower oil → small sardines or bullet tuna in extra virgin olive oil or its own juices
Habits that help
- Grind flax or chia seeds in a grinder before eating them. Store them in an opaque, airtight jar in the fridge to stop them going rancid.
- Keep nuts and oils rich in omega-3 in a cool place away from light to prevent their polyunsaturated fatty acids from oxidising.
- Cook oily fish gently, for example en papillote, in a moderate oven or on a low-heat griddle. Avoid prolonged frying, which degrades the fats.
- Plan your weekly shop to include at least three servings of sustainably sourced fish, prioritising oily fish, and a jar of raw walnuts in the cupboard.
- If you follow a vegetarian or vegan diet, plan daily sources of ALA. If you need DHA from microalgae, your doctor or dietitian-nutritionist will recommend it.
Omega-3 is a family of fats that the body cannot make, so you need to get them from food. The main sources are oily fish and seafood, as well as walnuts and some seeds.
These foods do not provide the same types of omega-3, and the body does not use them in the same way. Two questions often come up in consultations: how many servings a week are enough, and which fish should you choose because of mercury? It also helps to understand the difference between omega-3 from fish and plant sources.
What is omega-3, and why do you need it?
Omega-3s are a family of polyunsaturated fats that form part of every cell membrane. They play a role in vision and the nervous system, and in producing substances that regulate blood clotting and inflammation. Your body cannot make them, so you need to get them from food.
Three types matter in the diet. Alpha-linolenic acid (ALA) is found in seeds, walnuts and some vegetable oils. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in fish, seafood and microalgae. The Autoridad Europea de Seguridad Alimentaria (EFSA) notes that the body can convert some ALA into EPA and DHA, but only in limited amounts [1]. It is therefore useful to include sources of both types.
Which foods contain the most omega-3 per 100 grams?
Fish provides EPA and DHA in a form the body can use directly. Seeds and nuts provide ALA, which is more concentrated but less readily used. The amounts of these different types cannot therefore be compared directly.
Here are the amounts per 100 g of raw food, from the US Department of Agriculture’s FoodData Central database [2]. For fish, the figures combine EPA and DHA; for seeds, walnuts and oil, they show ALA:
- Mackerel: 2.3 g of EPA and DHA [2]
- Farmed salmon: 2.0 g of EPA and DHA [2]
- Anchovies: 1.4 g of EPA and DHA [2]
- Sardines in oil, drained: 1.0 g of EPA and DHA [2]
- Trout: 0.7 g of EPA and DHA [2]
- Flaxseed oil: 53.4 g of ALA [2]
- Flaxseeds: 22.8 g of ALA [2]
- Chia seeds: 17.8 g of ALA [2]
- Walnuts: 9.1 g of ALA [2]
These figures are estimates: the fat content of fish varies by species, season and whether it is wild or farmed.
There is one practical point about flax and chia: their outer coating is fibre that the gut cannot break down. If you eat them whole, much of each seed passes through undigested, so you do not benefit from its ALA. Eat them ground or crushed.
What is the difference between plant-based omega-3 and that from fish?
The difference lies in how your body uses each type. EPA and DHA from fish can be used as they are. Plant-based ALA has its own functions, but the liver converts only a small amount into EPA and DHA.
EFSA notes that this conversion is limited, and even lower for DHA [1]. A handful of walnuts is a good source of ALA. If you are looking for EPA and DHA, though, it is not a substitute for a serving of sardines.
If you follow a vegetarian or vegan diet, include walnuts, chia or ground flaxseed every day. If a direct source of DHA from microalgae would be useful, your doctor or dietitian-nutritionist will recommend it.
How much omega-3 do you need each day, and how can you get it?
EFSA’s reference intake for adults is 250 mg of EPA and DHA a day [1]. For ALA, the reference is 0.5% of daily energy intake [1]. On a diet of around 2,000 kcal, that is about 1.1 g a day.
During pregnancy and breastfeeding, EFSA recommends an additional intake of DHA [1]. Your healthcare team assesses whether you need it. DHA contributes to the development of a baby’s brain and vision.
In practice, you can meet these reference intakes without supplements. The daily 250 mg adds up to about 1,750 mg a week. One 120 g serving of mackerel provides around 2.8 g of EPA and DHA [2]. AESAN recommends at least three servings of fish a week, prioritising oily fish [3]. For ALA, around 30 g of walnuts, six or seven, is enough, providing about 2.7 g. A tablespoon of ground flaxseed, around 10 g, provides about 2.3 g [2]. See “Omega-3 and the brain”.
Which fish should you choose to avoid mercury?
Oily fish is the best source of EPA and DHA, but large, long-lived fish accumulate methylmercury through the marine food chain.
The Agencia Española de Seguridad Alimentaria y Nutrición (AESAN) recommends eating a variety of species to reduce mercury exposure [3]. Prioritise those with lower levels, such as sardines, anchovies, mackerel, horse mackerel, herring and salmon.
The same agency advises avoiding four species during pregnancy, if you could become pregnant, while breastfeeding and for children up to the age of 10. These are swordfish, bluefin tuna (Thunnus thynnus), shark (dogfish, porbeagle, spurdog, small-spotted catshark and blue shark) and pike. For children aged 10 to 14, it recommends limiting these fish to 120 g a month [3]. For other adults, alternating between smaller species is enough. See “Fish and mercury while breastfeeding”.
Do you need omega-3 supplements?
Most people do not. A varied diet with at least three servings of fish a week, prioritising oily fish [3], plus walnuts or seeds every day can help you meet EFSA’s reference intakes without supplements.
Supplements have specific uses. If you need them, your doctor or dietitian-nutritionist will recommend them. If you take anticoagulants or antiplatelet medicines, speak to your doctor before taking any omega-3 supplement.
How do these foods affect inflammation and heart health?
Omega-3s play a part in producing eicosanoids. The body uses these substances as signals to switch inflammation on and off. Omega-3s support the production of those that help moderate it. This is one reason why oily fish, walnuts and seeds are part of an anti-inflammatory diet. No single food treats inflammation on its own.
The effect on heart health is more modest than it is sometimes made out to be. A Cochrane review brought together 86 trials involving more than 162,000 people; most looked at supplements. It concluded that increasing EPA and DHA makes little difference to overall mortality or overall cardiovascular risk. It also found that they lower triglycerides and probably slightly reduce coronary events [4]. Increasing ALA may slightly reduce cardiovascular events and arrhythmias [4].
If your aim is to improve your cholesterol and triglyceride levels, consider your overall eating pattern. The benefit does not come from one nutrient in isolation.
What common mistakes do we see in consultations?
Eating flax or chia seeds whole and expecting to benefit from all their ALA. Much of each seed passes through undigested because the gut cannot break down its outer coating.
Avoiding all fish because of mercury. Larger species accumulate more; eating a variety and choosing smaller fish reduces exposure [3].
Ensuring an optimal omega-3 intake does not require special products or trendy supplements. You can eat at least three servings of fish a week, prioritising oily fish, and have walnuts or ground seeds every day.
If you live with an autoimmune condition, joint problems or chronic pain, you can speak to our team of dietitians-nutritionists specialising in anti-inflammatory nutrition. We tailor each plan to your medical situation and personal circumstances, in Barcelona and online.
Your first step this week
Two tins of sardines or mackerel in the cupboard
They make a quick supper or salad with EPA and DHA. Choose fish in their own juices or extra virgin olive oil.
A jar of raw walnuts for breakfast or a snack
Six or seven walnuts a day, about 30 g, more than cover the daily reference intake for ALA.
A small jar of ground flax or chia seeds in the fridge
A tablespoon in yoghurt, a vegetable soup or oats adds ALA and fibre to the dish.
When to see a doctor
When to see a doctor
“Anti-inflammatory” describes an eating pattern, not a treatment. Food can support you and improve how you feel; it does not cure an autoimmune disease, does not replace medication and no diet can switch off chronic inflammation.
If you are eating more omega-3 because you have joint pain or swelling, arrange a medical appointment without waiting to change your diet if you notice any of these signs:
- A joint is hot, red and swollen, and you have a fever [5]
- One or more joints are swollen and the swelling has not gone down after six weeks [5]
- Your hands or feet feel stiff for more than half an hour after you wake up [5]
- You lose weight without trying, have a persistent fever or experience night sweats [6]
A hot, red joint with a fever: go to the emergency department today. An infection in the joint needs to be ruled out. Swelling lasting more than six weeks: contact your GP this week. You need a referral to rheumatology within the following six weeks; with arthritis, starting early changes the prognosis.
Migraine, fibromyalgia and EPOC have their own warning signs. If you live with any of these conditions, review them with your doctor.
Food may help you feel better, particularly when it supports your treatment instead of replacing it.
Every case is different
General guidance can only take you so far. The next step is to look at your situation in a consultation.
Keep reading
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Resource hubOther conditions: diet and nutrition guides
Nutrition as part of your treatment
How we work: first visit, eating plan and follow-up
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA Journal. 2010;8(3):1461. doi:10.2903/j.efsa.2010.1461
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central: SR Legacy. Beltsville (MD): USDA ARS; 2019. Available at: https://fdc.nal.usda.gov
- Agencia Española de Seguridad Alimentaria y Nutrición (AESAN). Recomendaciones de consumo de pescado por presencia de mercurio. Madrid: AESAN; 2019. Available at: https://www.aesan.gob.es/dam/jcr:37655af5-1ba6-4a9e-a756-79a51810aac7/RECOMENDACIONES_consumo_pescado_MERCURIO_AESAN_WEB.pdf
- Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020;3(3):CD003177. doi:10.1002/14651858.CD003177.pub5
- Combe B, Landewe R, Daien CI, et al. 2016 update of the EULAR recommendations for the management of early arthritis. Ann Rheum Dis. 2017;76(6):948-959. doi:10.1136/annrheumdis-2016-210602
- National Institute for Health and Care Excellence (NICE). Suspected cancer: recognition and referral. NICE guideline NG12. London: NICE; 2015 (updated in 2026). Available at: https://www.nice.org.uk/guidance/ng12
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