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Fish oil supplements are often promoted as an investment in our future health. A daily capsule might promise support for the heart, brain and general wellbeing. And because omega-3 fatty acids are important nutrients, taking a little extra can seem like a sensible precaution.
But does it actually make a difference?
Omega-3s are important for good health. What isn't so clear is whether taking additional amounts in supplement form offers the protection we might expect.
There's an important difference between getting enough of a nutrient and benefiting from taking more of it.
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One thing worth knowing: Omega-3s are important for health, but taking additional supplements hasn't consistently been shown to prevent heart disease, stroke or dementia in generally healthy adults.
One thing to ponder: Are you considering an omega-3 supplement because your diet may not provide enough, or because you're hoping for additional protection against illness?
One thing to experiment with: Look at where you get omega-3s in your diet. Could you include a portion of oily fish this week, perhaps tinned sardines or mackerel? If you already take a supplement, check how much EPA and DHA it actually provides.
Why do we need omega-3 fatty acids?
Omega-3s are a family of polyunsaturated fatty acids involved in several important functions throughout the body.
They form part of our cell membranes, contribute to the normal structure and function of the brain and eyes, and participate in processes involved in inflammation, blood clotting and cardiovascular function.
Three types are particularly relevant.
ALA (alpha-linolenic acid) is an essential fatty acid, meaning our bodies cannot produce it and we must obtain it through food. Good sources include walnuts, chia seeds, linseeds and rapeseed oil.
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are long-chain omega-3 fatty acids found mainly in oily fish and certain algae-derived products.
DHA is particularly abundant in the brain and retina, where it forms part of the membranes surrounding cells, including nerve cells. EPA and DHA also take part in cell signalling and processes that influence inflammation and blood clotting.
Our bodies can convert some ALA into EPA and DHA, but this conversion is limited, particularly for DHA. That's why oily fish is a useful dietary source.
These biological functions explain why omega-3s matter. They don't, however, establish that taking more in the form of supplements will necessarily improve our health.
Can we get enough omega-3s from food?
The NHS recommends eating at least two portions of fish each week, including one portion of oily fish. A portion is approximately 140 g. [1]
This recommendation is intended to provide an average of around 450 mg of long-chain omega-3s per day across the week, according to the UK's Scientific Advisory Committee on Nutrition (SACN), as a population dietary reference, not a precise daily requirement or a threshold for deficiency. The actual amount obtained varies with the fish we eat. [2]
Salmon, sardines, mackerel, herring and trout are all examples of oily fish. Fresh and canned tuna, despite their nutritional value, don't count towards the NHS oily-fish recommendation.
And eating oily fish doesn't have to mean buying expensive wild Alaskan salmon.
Tinned sardines and mackerel are affordable, convenient alternatives that provide EPA and DHA alongside several other valuable nutrients.
They supply high-quality protein, which helps maintain muscle and other body tissues, and vitamin B12, needed for normal nerve function and healthy red blood cells. Oily fish also provides vitamin D, which contributes to bone and muscle health and normal immune function, along with minerals such as selenium and phosphorus.
Sardines with their soft, edible bones are particularly useful sources of calcium and phosphorus, both important for maintaining healthy bones.
This is a meaningful distinction between food and supplements.
A conventional fish oil capsule provides omega-3s, but not the protein and most of the other nutrients found in fish.
That doesn't make supplements inherently inferior. They serve a different nutritional purpose and can be useful when dietary intake is limited.
For women who haven't yet been through menopause, including during perimenopause, the NHS recommends no more than two portions of oily fish weekly because certain environmental contaminants can build up in the body over time. [1]
Plant foods such as walnuts, chia seeds and linseeds also contribute omega-3s, primarily ALA. For people who don't eat fish, algae-derived supplements can provide DHA, sometimes alongside EPA.
Not eating oily fish regularly isn't automatically evidence of a nutritional deficiency. But it is a reason to consider whether our usual diet provides sufficient long-chain omega-3s.
The next question is whether taking additional EPA and DHA offers health benefits beyond meeting our nutritional needs.
Do omega-3 supplements protect against heart disease and stroke?
Omega-3 supplements have been studied extensively for cardiovascular prevention.
The results are more complicated than saying that fish oil is good for the heart. A large 2020 Cochrane review brought together 86 randomised trials involving approximately 163,000 participants. It found that increasing EPA and DHA intake had little or no effect on deaths from any cause, overall cardiovascular events or strokes. There was evidence of possible small reductions in coronary heart disease events, although these findings were less certain. [3]
Coronary heart disease affects the arteries supplying blood to the heart muscle. When blood flow is reduced, the heart muscle may not receive enough oxygen, resulting in a heart attack, if the lack of blood supply is severe or prolonged enough.
One of the largest studies, the VITAL trial followed more than 25,000 adults for approximately five years, comparing daily marine omega-3 supplements with a placebo.
Taking omega-3 supplements did not clearly reduce the overall risk of heart attack, stroke or cardiovascular death. There were fewer heart attacks among those taking supplements, but the difference was modest: around 4 fewer heart attacks for every 1,000 people over five years. The researchers also observed potentially greater benefits among participants who ate fewer than 1.5 servings of fish per week, although this finding needs confirmation. [4]
So, while the results suggest that some people might benefit, they don't provide convincing evidence that taking fish oil every day offers substantial additional cardiovascular protection for generally healthy adults.
What about lowering triglycerides?
Omega-3 supplements can lower triglycerides, a type of fat circulating in the blood, particularly at higher doses.
But here's a distinction worth understanding.
Improving a number on a blood test isn't necessarily the same as improving someone's health.
A treatment might lower triglycerides without necessarily preventing heart attacks or strokes. This doesn't mean that triglycerides are irrelevant to cardiovascular risk. It means we need evidence that a particular treatment improves the outcomes we're trying to prevent, rather than relying entirely on a change in a blood marker.
Clinical trials have illustrated this distinction. The STRENGTH trial tested a high-dose combination of EPA and DHA in people at elevated cardiovascular risk. Despite lowering triglycerides, the treatment did not reduce major cardiovascular events. [5] Another trial, REDUCE-IT, found that a prescription-only medicine containing purified EPA, called icosapent ethyl (Vazkepa), reduced cardiovascular events in selected high-risk patients already receiving statins. [6] The preparations, study populations and trial designs differed, and the reasons for their contrasting results remain debated.
The important point is that benefits demonstrated with a particular prescription medicine cannot automatically be extended to ordinary fish oil capsules.
What do cardiovascular experts recommend?
NICE, the UK's National Institute for Health and Care Excellence, advises against using ordinary omega-3 products to prevent cardiovascular disease. [7] There is a specific exception for eligible patients who may benefit from prescription icosapent ethyl alongside their existing treatment. [8]
The European Society of Cardiology and European Atherosclerosis Society also advise against using ordinary omega-3 supplements to reduce cardiovascular risk. [9]
European cardiovascular guidelines also support a healthy dietary pattern that includes fish, vegetables, fruit and wholegrains. [10] Their advice makes an important distinction between obtaining nutrients through our diet and using supplements as treatments to prevent disease. Ordinary omega-3 supplements aren't recommended as a substitute for established cardiovascular prevention strategies.
Do omega-3 supplements improve memory or prevent dementia?
DHA forms part of the membranes of nerve cells in the brain and contributes to their normal structure and function. But does taking more DHA improve memory or protect against dementia?
Research has produced mixed results.
A 2025 meta-analysis combining 58 randomised trials reported improvements in several aspects of cognitive performance, including measures of memory and visuospatial ability. [11]
These findings deserve attention. However, the results varied substantially between studies, and many trials had methodological limitations. For example, the studies included people with different levels of cognitive ability, used different supplement doses and lasted for different lengths of time. They also measured cognitive performance in different ways. Nearly 40% of the trials were rated as poor quality by the review authors. [11]
Another review published in 2025, focusing on older adults without cognitive impairment, found no significant improvement in overall cognitive performance. [12]
There's also a distinction between performing better on a cognitive test and experiencing a meaningful improvement in everyday life. For example, a higher score on a test of memory or attention doesn't necessarily mean someone will learn more effectively, perform better at work or remain independent for longer as they age. These are outcomes that matter to people, and they haven't been established by the positive findings.
Nor does improved performance on an individual cognitive test demonstrate that supplementation prevents dementia.
The World Health Organization's updated 2026 guidance continues to recommend against routinely taking omega-3 supplements specifically to prevent cognitive decline or dementia in people without a diagnosed nutritional deficiency. [13]
This doesn't rule out the possibility that certain individuals might benefit from supplementation. It means the evidence isn't currently strong enough to recommend it routinely for that purpose.
Are supplements better than eating fish?
A 2025 study published in the British Journal of Nutrition compared fish oil supplements with oily fish in 42 adults over 12 weeks. [14] The supplement group showed changes in certain tiny particles circulating in the blood that are involved in blood clotting. The oily-fish group didn't show the same effects. The researchers also observed differences in laboratory measurements related to thrombin, a substance involved in clot formation.
At first glance, these findings might suggest that fish oil capsules offer advantages over eating fish. But there's an important detail. The supplement group received approximately 1,500 mg of EPA daily, compared with approximately 400 mg in the oily-fish group. Their DHA intakes were similar. [14]
So the interventions didn't simply compare the same amounts of omega-3s delivered through different sources. They also differed considerably in EPA dose. Both interventions increased omega-3 levels in blood-cell membranes. And importantly, the researchers measured biological changes associated with clotting. They didn't measure heart attacks, strokes or cardiovascular deaths.
The findings are scientifically interesting and may help researchers understand how EPA influences these processes. What they don't establish is that fish oil supplements protect the heart better than eating oily fish. It's another example of why we need to distinguish changes in biological measurements from improvements in health outcomes.
If you decide to take a supplement, what matters?
There are circumstances in which supplementing EPA and DHA may be a practical choice, particularly for people who rarely or never eat oily fish. But the amount, quality and purpose of the supplement deserve attention.
Check what you're actually getting
The British Dietetic Association doesn't recommend omega-3 supplements for the general UK population because the evidence of additional health benefits is inconclusive.
For anyone who chooses to take one, its guidance suggests a daily supplement providing approximately 450 mg of EPA and DHA combined, comparable to the UK dietary reference. [15]
Check the EPA and DHA amounts on the label, rather than the total amount of fish oil. For example, a capsule labelled 1,000 mg fish oil might provide approximately 180 mg EPA and 120 mg DHA, giving a combined total of 300 mg. That doesn't mean the product is poor quality, it simply illustrates why the amount of fish oil isn't the same as the amount of EPA and DHA.
Are there any risks or side effects?
Fish oil supplements are generally well tolerated, although some people experience an unpleasant aftertaste, reflux, nausea or digestive discomfort.
There have also been concerns about bleeding because omega-3s can influence processes involved in blood clotting. A large 2024 review of randomised trials found no significant overall increase in bleeding among people taking omega-3 supplements. However, high-dose prescription EPA was associated with a 50% relative increase in bleeding risk. In absolute terms, this amounted to approximately 6 additional bleeding events per 1,000 people treated. [16]
If you take medication that affects blood clotting, such as warfarin, apixaban, rivaroxaban, aspirin or clopidogrel, it's sensible to check with your clinician or pharmacist before starting a supplement.
Higher doses deserve particular attention for another reason. A 2026 analysis of 35 randomised trials found an increased risk of atrial fibrillation, an abnormal heart rhythm, among people at elevated cardiovascular risk taking high-dose omega-3 supplements. The same statistically significant increase wasn't found in the lower-dose groups. [17] Fish oil supplements are not dangerous, but higher doses aren't automatically better.
How well are fish oil supplements regulated?
In the UK, fish oil supplements are regulated as foods, not medicines. Manufacturers must follow food safety and labelling rules, and there are restrictions on the health benefits they can advertise. However, they don't have to prove that their individual supplements improve health before selling them. [18]
A licensed medicine, by comparison, must have sufficient evidence that it works for its intended medical use and that its benefits outweigh its risks. For example, a fish oil supplement may carry an authorised claim about DHA contributing to normal brain function. That doesn't mean the product has been shown to improve memory or prevent dementia.
What about quality and freshness?
Fish oil can deteriorate through oxidation and become rancid. [19] If you choose to take a supplement, look for a product that has been independently tested for its EPA and DHA content, contaminants and freshness. Follow the manufacturer's storage instructions and avoid products that smell or taste rancid.
Cod liver oil is also worth distinguishing from ordinary fish oil because it contains vitamins A and D. Excess vitamin A can be harmful, particularly during pregnancy or when trying to conceive.
So, do you really need an omega-3 supplement?
Omega-3s matter for our health and getting enough is a sensible nutritional goal.
But taking additional amounts doesn't automatically provide greater protection against heart disease, stroke or dementia.
For many people, the useful starting point is simply to look at their diet.
Could you include a portion of oily fish weekly in your meals? Would tinned sardines or mackerel be a convenient option? Are there plant sources of omega-3s already included in your diet?
And if eating fish is not an option, might an algae-derived or fish oil supplement help meet your nutritional needs?
There's room for both food and supplements, depending on individual circumstances. What matters is being clear about the need and purpose of supplementation.
Omega-3s are important for health, but whether taking more supplements improves our health is another matter.
When a supplement label promises a benefit, it's worth asking: what actually improved in the research, and would that improvement make a meaningful difference in someone’s life?
If you'd like help finding a way of eating that supports your health, your goals and your life, get in touch. We can arrange a free discovery call to talk about what matters to you and whether coaching could help.
References
NHS. Fish and shellfish: Nutrition.
Scientific Advisory Committee on Nutrition and Committee on Toxicity. (2004). Advice on Fish Consumption: Benefits and Risks.
Abdelhamid AS et al. (2020). Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews.
Manson JE et al. (2019). Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer. New England Journal of Medicine.
Nicholls SJ et al. (2020). Effect of High-Dose Omega-3 Fatty Acids vs Corn Oil on Major Adverse Cardiovascular Events in Patients at High Cardiovascular Risk: The STRENGTH Randomized Clinical Trial. JAMA. https://doi.org/10.1001/jama.2020.22258
Bhatt DL et al. (2019). Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia. New England Journal of Medicine. https://doi.org/10.1056/NEJMoa1812792
NICE. Cardiovascular disease: Risk assessment and reduction, including lipid modification. NG238.
NICE. (2022). Icosapent ethyl with statin therapy for reducing cardiovascular events. TA805.
European Society of Cardiology and European Atherosclerosis Society. (2025). Focused Update of the Dyslipidaemia Guidelines. European Heart Journal.
Visseren FLJ et al. (2021). 2021 ESC Guidelines on cardiovascular disease prevention in clinical practice. European Heart Journal, 42, 3227–3337.
Shahinfar H et al. (2025). A systematic review and dose response meta analysis of Omega 3 supplementation on cognitive function. Scientific Reports.
Mulargia R et al. (2025). Exploring the Preventive Effects of Omega-3 Polyunsaturated Fatty Acids Supplementation on Global Cognition. Clinical and Translational Neuroscience.
World Health Organization. (2026). Risk Reduction of Cognitive Decline and Dementia: WHO Guidelines, Second Edition.
Sharman A et al. (2025). High-dose fish oil supplements are more effective than oily fish in altering the number and function of extracellular vesicles in healthy human subjects. British Journal of Nutrition.
British Dietetic Association. (2021). Omega-3 Food Fact Sheet. Currently under review.
Javaid M et al. (2024). Bleeding Risk in Patients Receiving Omega-3 Polyunsaturated Fatty Acids: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Journal of the American Heart Association, 13.
Abuknesha NR et al. (2026). Effects of Omega-3 Fatty Acid Treatment on Risk for Atrial Fibrillation: An Updated Meta-Analysis of 35 Trials including 114,592 Individuals. Circulation: Arrhythmia and Electrophysiology.
UK Government. Food Supplements: Regulatory Guidance.
Jairoun AA, Shahwan M, Zyoud SH. (2020). Fish oil supplements, oxidative status, and compliance behaviour: Regulatory challenges and opportunities. PLOS ONE, 15(12).