Fish oil supplements, rich in omega-3 fatty acids EPA and DHA, are widely used by women across different life stages for various health reasons. From supporting foetal development during pregnancy to maintaining cardiovascular health and potentially aiding cognitive function, fish oil has become a popular dietary supplement in the UK. However, understanding the evidence behind fish oil benefits for women, appropriate dosages, potential side effects, and when supplementation is truly beneficial requires careful consideration. This article examines the current evidence and UK guidance to help women make informed decisions about fish oil supplementation.

What Is Fish Oil and Why Do Women Take It?

Fish oil is a dietary supplement derived from the tissues of oily fish such as mackerel, salmon, sardines, and anchovies. It is particularly rich in omega-3 polyunsaturated fatty acids, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These long-chain omega-3 fatty acids are not produced in large amounts by the human body, making dietary sources or supplements important for practical intake.

Women across different life stages take fish oil for various health reasons. During pregnancy and breastfeeding, omega-3 fatty acids support foetal brain and eye development. The European Food Safety Authority (EFSA) recognises that maternal DHA intake contributes to normal brain and eye development in the foetus and breastfed infants, though evidence for long-term cognitive benefits remains mixed. Many women also use fish oil to support cardiovascular health, as omega-3s may help maintain healthy triglyceride levels and support normal heart function. Some women take fish oil during menopause or for bone health, although current evidence for these uses is limited and inconclusive.

The popularity of fish oil supplementation among women has increased partly due to dietary patterns in the UK, where many individuals do not consume the recommended two portions of fish per week (one of which should be oily fish) as advised by the NHS Eatwell Guide. Fish oil supplements offer an alternative for those who dislike fish or follow plant-based diets, with algal oil providing a vegetarian/vegan source of DHA. Some women choose supplements due to concerns about environmental contaminants in fish, though the NHS advises that the benefits of eating fish generally outweigh the risks. However, it is important to recognise that supplements should complement, not replace, a balanced diet rich in whole foods.

Before starting any supplementation regimen, women should consider their individual health needs, existing medical conditions, and current medications, as fish oil may interact with certain treatments or be contraindicated in specific circumstances.

Recommended Dosage and How to Take Fish Oil Safely

The appropriate dosage of fish oil varies depending on individual health goals and existing medical conditions. For general health maintenance, the NHS recommends consuming one to two portions of oily fish weekly. The European Food Safety Authority (EFSA) suggests around 250 mg of combined EPA and DHA daily for adults. When supplementing, most products contain between 250 mg and 1,000 mg of omega-3 fatty acids per capsule, though the exact EPA and DHA content varies considerably between brands.

For specific therapeutic purposes such as high triglycerides, higher doses may be prescribed by healthcare professionals. Prescription-only omega-3-acid ethyl esters (such as Omacor) are licensed in the UK at doses of 2–4 grams daily for hypertriglyceridaemia, as per the British National Formulary (BNF). It's important to note that NICE guideline NG238 advises against omega-3 supplements for routine cardiovascular disease prevention, though NICE technology appraisal TA805 supports icosapent ethyl (a specific prescription omega-3) for selected high-risk patients.

Pregnant and breastfeeding women should exercise particular caution with fish oil supplements. Whilst omega-3 fatty acids are beneficial for foetal development (EFSA recommends 200 mg of DHA daily during pregnancy), it is essential to choose products specifically formulated for pregnancy that are free from vitamin A (retinol), as excessive vitamin A intake can harm the developing baby. The NHS specifically advises pregnant women to avoid cod liver oil supplements for this reason.

To optimise absorption and minimise side effects, fish oil capsules should be taken with meals, preferably those containing some dietary fat. This enhances the bioavailability of omega-3 fatty acids and reduces the likelihood of gastrointestinal discomfort. Capsules should be stored in a cool, dark place to prevent oxidation, and any products with a strong fishy odour or past their expiry date should be discarded. Women taking warfarin should have their INR monitored when starting fish oil, particularly at higher doses. Those taking direct oral anticoagulants (DOACs) such as apixaban or rivaroxaban, or antiplatelet drugs like aspirin or clopidogrel, should discuss fish oil use with their healthcare provider due to potential increased bleeding risk.

Potential Side Effects and Who Should Avoid Fish Oil

Fish oil supplements are generally well tolerated by most women, but several common side effects may occur, particularly when starting supplementation or taking higher doses. The most frequently reported adverse effects include gastrointestinal symptoms such as nausea, loose stools, indigestion, and a fishy aftertaste or 'fish burps'. These effects can often be minimised by taking capsules with meals, choosing enteric-coated formulations, or temporarily reducing the dose before gradually increasing it.

Some women may experience mild bleeding or bruising more easily when taking fish oil, due to its antiplatelet effects. Whilst this is rarely clinically significant at standard supplementation doses, it becomes more relevant for women taking anticoagulant medications or antiplatelet drugs. Women taking warfarin should have their INR monitored when starting fish oil supplements, particularly at higher doses. Those taking direct oral anticoagulants or antiplatelet drugs should be clinically monitored for signs of bleeding. If you're scheduled for surgery, inform your surgical team about fish oil use and follow their specific pre-operative advice regarding supplement cessation.

Allergic reactions to fish oil supplements can occur in women with fish or shellfish allergies, though the risk varies depending on the purity and processing of the product. Symptoms may include rash, itching, swelling, or in rare cases, anaphylaxis. If you experience severe allergic symptoms such as difficulty breathing, swelling of the face or throat, or feeling faint, seek emergency medical help immediately (call 999). Women with known seafood allergies should discuss alternative omega-3 sources, such as algal oil supplements, with their healthcare provider.

High-dose fish oil (prescription omega-3-acid ethyl esters) may be associated with additional risks including a potential increase in atrial fibrillation and, in some cases, a rise in LDL cholesterol when used for hypertriglyceridaemia. These treatments should only be used under medical supervision. Women with very high triglycerides (fasting levels ≥10 mmol/L) should be referred for specialist assessment due to pancreatitis risk.

If you experience persistent side effects or any concerning symptoms whilst taking fish oil, contact your GP promptly for assessment. For prescribed omega-3 medicines, suspected adverse reactions can be reported through the MHRA Yellow Card scheme.

Fish Oil Benefits for Women's Heart and Brain Health

The cardiovascular effects of omega-3 fatty acids have been extensively studied, with evidence suggesting several mechanisms through which fish oil may influence women's heart health. EPA and DHA help reduce triglyceride levels, a type of fat in the blood that, when elevated, increases cardiovascular disease risk. They also possess anti-inflammatory properties that may help reduce chronic inflammation associated with atherosclerosis. Some research indicates that omega-3 fatty acids may contribute to modest reductions in blood pressure and improvements in endothelial function, supporting healthy blood vessel flexibility.

However, it is important to note that recent large-scale trials have produced mixed results regarding fish oil supplementation and cardiovascular event prevention. NICE guideline NG238 specifically advises against offering omega-3 supplements for the prevention of cardiovascular disease. For individuals with established cardiovascular disease and elevated triglycerides, NICE technology appraisal TA805 supports the use of icosapent ethyl (a specific prescription omega-3 product) in selected high-risk patients, but this evidence does not extend to over-the-counter fish oil supplements. Women concerned about cardiovascular health should prioritise evidence-based interventions including smoking cessation, regular physical activity, a Mediterranean-style diet, and appropriate medications such as statins or antihypertensives where indicated.

Regarding cognitive and brain health, DHA is a major structural component of brain cell membranes and plays a role in neuronal function and communication. Observational studies suggest that higher omega-3 intake is associated with better cognitive performance and potentially reduced risk of age-related cognitive decline in women. However, clinical trials have shown inconsistent results, and there is currently insufficient evidence to recommend fish oil supplements specifically for cognitive protection or enhancement. Some research has explored fish oil's role in supporting mental wellbeing, with modest evidence suggesting potential benefits for mild depressive symptoms, though findings remain inconsistent and further research is needed.

For menopausal women, there is emerging interest in whether omega-3 supplementation might help manage symptoms such as hot flushes or support bone health, though current evidence remains limited and inconclusive. Women experiencing menopausal symptoms should discuss evidence-based management options with their GP, which may include lifestyle modifications, hormone replacement therapy (HRT) where appropriate, or other proven interventions. Whilst fish oil supplementation is unlikely to cause harm and may offer general health benefits, there is no established link between omega-3 intake and significant improvement in menopausal symptoms, and it should not be relied upon as a primary treatment approach.

Frequently Asked Questions