Omega-3 (EPA + DHA)
Marine fatty acids with cardiovascular and brain benefits
What is Omega-3 (EPA + DHA)?
Omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are long-chain polyunsaturated fats found primarily in oily fish. They are considered 'essential' because the body cannot synthesise them efficiently from plant-based ALA (found in flaxseed, walnuts). DHA is the predominant structural fat in the brain (comprising 15–20% of total brain fat) and retina. EPA is primarily anti-inflammatory.
How it works
EPA and DHA are incorporated into cell membrane phospholipids, replacing pro-inflammatory omega-6 fatty acids and altering membrane fluidity, receptor function, and signal transduction. They competitively inhibit arachidonic acid metabolism, reducing production of inflammatory eicosanoids (thromboxane A2, leukotriene B4). DHA also converts to resolvins and protectins — specialised pro-resolving mediators (SPMs) that actively terminate inflammation.
What the evidence shows
Cardiovascular: The REDUCE-IT trial (2018, 8,179 patients) showed 4g EPA (icosapentaenoic acid) daily reduced major cardiovascular events by 25% in high-risk patients. Brain/cognition: DHA is essential for neuronal membrane health; supplementation in pregnant women improves infant cognitive outcomes (multiple RCTs). Depression: 2019 Cochrane review found omega-3 supplements had a clinically meaningful effect on depression. Triglycerides: consistently reduced by 20–50% in RCTs.
When to expect results
Measurable changes in blood EPA/DHA levels begin. Subtle reductions in inflammatory markers in some people.
Mood improvements notable in those with low baseline omega-3. DOMS (muscle soreness after exercise) may reduce.
Triglyceride levels measurably lower. Joint pain and stiffness reduced in people with inflammatory conditions.
Full cardiovascular and cognitive protective benefits accumulating. Red blood cell omega-3 index (ideal: above 8%) reaches target range.
Dosing
For general health: 1–2g combined EPA+DHA daily. For cardiovascular risk reduction: 2–4g daily. For depression: most trials use 1–2g EPA specifically. UK NHS recommends 2 portions of oily fish weekly (provides ~1g EPA+DHA/day) — most people don't hit this. Look for products with >60% EPA+DHA concentration by weight.
Forms to choose
Fish oil (most common), krill oil (better absorption but lower dose per capsule, more expensive), algal oil (vegan, directly provides DHA+EPA without the fish intermediate). Triglyceride form absorbs better than ethyl ester (check the label). Store in fridge after opening to prevent oxidation — rancid fish oil tastes unpleasant and may be harmful.
Who benefits most
Everyone who doesn't eat 2+ portions of oily fish weekly (the majority of UK adults). Specifically: people with cardiovascular risk factors, anyone with depression or low mood, pregnant or breastfeeding women (DHA for infant brain), older adults (cognitive protection), athletes (reduces exercise-induced inflammation and DOMS).
Who should avoid / caution
Fish/shellfish allergy (use algal oil instead). People on anticoagulants (warfarin, apixaban) should discuss with GP — fish oil may enhance blood-thinning. Those with fish/seafood allergies should use algal omega-3.
Interactions & stacking
Both fat-soluble and absorbed together. Excellent to take in the same meal. D3 and omega-3 have complementary anti-inflammatory effects.
Paired for cardiovascular support. Both reduce inflammation and support mitochondrial function.
Omega-3 at high doses (3g+/day) may potentiate anticoagulant effects. Monitor INR with GP if combining.
Vitamin E protects omega-3 from oxidation both in the capsule and in the body. Many quality fish oil products include vitamin E as a stabiliser.
Safety & side effects
Most common: fishy aftertaste (burping). Minimised by taking with food, choosing enteric-coated capsules, or refrigerating. High doses (above 3g/day) may thin blood — caution with anticoagulants. Very high doses may suppress immune function. Fish-source products are not suitable for vegans or people with fish allergies.
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This information is for educational purposes only and does not constitute medical advice. Always consult your GP or a qualified healthcare professional before starting any new supplement, particularly if you are pregnant, breastfeeding, have a medical condition, or are taking prescription medication.