Omega-3 benefits: what the evidence shows for heart, brain and eyes

Author: Adrianna Kalista

Adrianna Kalista

Passionate about writing and a graduate in clinical dietetics. She is particularly interested in phytotherapy and the effects of ketogenic nutrition on cognitive brain function.

Verification: Dr. Andreia Torres

Dr. Andreia Torres

Clinical nutritionist with a doctorate in health education. International expert in ketogenic nutrition.

What is omega-3 good for?

What is omega-3 good for? What omega-3 is good for is set in UK law by authorised claims: “EPA and DHA contribute to the normal function of the heart” (250 mg EPA and DHA a day), “DHA contributes to maintenance of normal brain function” and “DHA contributes to the maintenance of normal vision” (250 mg DHA a day) [21]. EPA, DHA and ALA are the three omega-3 fatty acids, and the strength of evidence is not the same for each [1][3]. A meta-analysis of 40 trials in 135 267 people also suggests a modestly lower heart attack risk, though total cardiovascular events were not significantly reduced; it was funded by GOED, the omega-3 industry body, and the lead author works for GOED [9]. Trials also show lower triglycerides, while body weight shows no effect and there are no meta-analyses for skin or hair [8][16].

EPA and DHA are long-chain omega-3s made at the base of the marine food chain by microalgae and other marine microorganisms [1]. ALA from plants raises DHA very little [3].

Are fish oil benefits the same as omega-3 benefits?

Are fish oil benefits the same as omega-3 benefits? Fish oil benefits overlap with omega-3 benefits because fish oil works through EPA and DHA, which fish obtain mainly from their diet; EPA and DHA are made at the base of the marine food chain by microalgae and other marine microorganisms [1]. Fish can make EPA and DHA only to a limited, species-dependent extent [1]. Algal oil raised blood EPA and DHA as effectively as fish oil in a 2025 randomised trial in 74 adults over 6 and 14 weeks, run by a producer of algal oil: five authors were dsm-firmenich employees and the sixth a contracted statistician [4].

EPA and DHA are the active molecules discussed when people ask about omega-3 fish oil benefits. In VITAL, 25 871 US adults took 1 g a day for 5.3 years; people eating less than 1.5 servings of fish a week had a hazard ratio of 0.81 for major cardiovascular events [10].

Is omega-3 good for your heart?

Is omega-3 good for your heart? Omega-3 is good for your heart in a modest, dose-related way: across 40 trials in 135 267 people, EPA and DHA reduced heart attack risk by about 13% (RR 0.87) and coronary death by about 9% (RR 0.91), but total cardiovascular events were not significantly reduced (RR 0.95); the meta-analysis was funded by GOED, the omega-3 industry body, and its lead author works for GOED [9]. In VITAL, 25 871 adults took 1 g a day for 5.3 years; major events were not significantly reduced (HR 0.92), while heart attacks were lower (HR 0.72) [10]. REDUCE-IT used 4 g of prescription icosapent ethyl, pure EPA in 8 179 patients on statins, while STRENGTH used 4 g EPA and DHA in 13 078 high-risk patients and was stopped with event rates of 12.0% versus 12.2% [11]. The risk of atrial fibrillation increased by about 12% at up to 1 g a day and about 51% above 1 g in large RCTs, mainly in people with heart disease or high risk [12]. “EPA and DHA contribute to the normal function of the heart”, with the effect at 250 mg a day [21].

What are omega-3 benefits for women?

What are omega-3 benefits for women? Omega-3 benefits for women are covered by the same authorised heart, brain and vision claims as for men [21]. A female-specific claim covers pregnancy and breastfeeding, with the effect at an extra 200 mg DHA a day on top of the adult 250 mg EPA and DHA: “Docosahexaenoic acid (DHA) maternal intake contributes to the normal brain development of the foetus and breastfed infants.” EFSA set 250 mg EPA plus DHA a day for adults, plus 100 to 200 mg DHA in pregnancy and breastfeeding [6].

For preterm birth, Cochrane found fewer preterm births with supplementation, but a newer meta-analysis of 37 trials did not confirm it (RR 0.92, 95% CI 0.83 to 1.01) [17]. The NHS advises women who may become pregnant to eat no more than 2 portions of oily fish a week and avoid fish liver oil supplements such as cod liver oil when pregnant or trying for a baby, because they are high in vitamin A (retinol) [18].

What are the signs of omega-3 deficiency?

What are the signs of omega-3 deficiency? Signs of omega-3 deficiency are not a reliable guide: low status is assessed using the omega-3 index, the share of EPA and DHA in red blood cell membranes [14]. No one has been observed below 2%, an observed minimum rather than a defined lower limit [14]. Zones proposed in 2004 classified below 4% as highest coronary risk and above 8% as lowest coronary risk [14]. The mean estimated from plasma in UK Biobank, not a representative sample, was 5.58% in 117 108 people, in the low range [14]. Adults aged 19 to 64 eat on average 56 g of oily fish a week, compared with the recommended 140 g, so foods high in omega-3 are the practical next step [19]. The index rises over weeks: 8 weeks in a study of 20 people [13].

Adding more oily fish to your week?

Mackerel, sardines or salmon go well on bread. Browse keto breads, bagels and tortillas in the BeKeto shop.

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Does omega-3 lower cholesterol?

Does omega-3 lower cholesterol? Omega-3 does not lower cholesterol: in a meta-analysis of 64 RCTs total cholesterol did not fall, while triglycerides fell by about 0.10 mmol/L per gram of omega-3 from fish oil [8]. DHA at 2 g a day or more raised LDL by about 0.19 mmol/L versus placebo, while EPA did not [8]. EFSA estimates the LDL rise at about 3% for 2 to 6 g EPA and DHA a day [7]. “DHA and EPA contribute to the maintenance of normal blood triglyceride levels”, with the effect at 2 g a day [21].

Which omega-3 source gives these benefits on a keto diet?

Which omega-3 source gives these benefits on a keto diet? The omega-3 source that gives these benefits is any source of EPA and DHA; flaxseed and echium oil provide ALA and did not raise the omega-3 index in a review of 13 RCTs [3]. One 175 g portion of farmed salmon still covers an adult’s weekly adequate intake as set by EFSA [2]. Cod liver oil also adds vitamins A and D, so check it against EFSA upper limits of 100 µg vitamin D and 3 000 µg RE vitamin A a day [5].

Verdict: for a fish-free keto diet, MEGA Omega 3 Vegan Algae Oil comes out best in our range because it is a vegan, fish-free oil from Schizochytrium microalgae with flavour from Sicilian lemon oil, and a 5 ml teaspoon gives 570 mg DHA and 185 mg EPA [20]. Do not exceed the recommended 5 ml serving. “This product is intended for adults. Not for use by children or by women who are pregnant or breastfeeding. If you take anticoagulant medication or are due to have surgery, consult your doctor before use.” [20]

Not eating oily fish every week?

MEGA Omega 3 Vegan is a microalgae oil that provides EPA and DHA ready formed: 570 mg DHA and 185 mg EPA in one 5 ml teaspoon.

£25.90

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This product is intended for adults. Not for use by children or by women who are pregnant or breastfeeding. If you take anticoagulant medication or are due to have surgery, consult your doctor before use.

How much omega-3 a day do you need for these benefits?

How much omega-3 a day do you need for these benefits? SACN’s UK guideline is 450 mg long-chain omega-3 a day, while EFSA set 250 mg EPA and DHA for adults [19][6]. For serving choices and claim thresholds, read how much omega-3 per day.

What are the side effects of omega-3?

What are the side effects of omega-3? In RCTs, omega-3 supplements did not increase bleeding (rate ratio 1.09, not significant, 11 trials, 120 643 people), but higher doses were linked to atrial fibrillation [12]. For dose bands and when to ask a clinician, read omega-3 side effects.

Is there a vegan omega-3 with the same benefits?

Is there a vegan omega-3 with the same benefits? Algal oil provides EPA and DHA without fish and raised blood levels as effectively as fish oil in 74 adults in a producer-run trial [4]. If you avoid fish, read our guide to vegan omega-3.

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