Omega-3 (EPA and DHA): Dosage, Benefits and Side Effects

EPA and DHA incorporate into cell membranes throughout the body, particularly in neural tissue, the retina, and inflammatory cells. They displace pro-inflammatory arachidonic acid, shifting the body's eicosanoid output toward less inflammatory prostaglandins and resolvins. DHA specifically is structural in synaptic membranes and the photoreceptor outer segments; EPA dominates in cardiovascular and inflammatory effects.

• Triglycerides: 2–4 g EPA+DHA/day lowers triglycerides 15–30%.
• Cardiovascular events: REDUCE-IT (icosapent ethyl 4 g/day) showed 25% reduction in major cardiovascular events.
• Inflammation: dose-dependent reductions in CRP and IL-6.
• Mood: meta-analyses support modest improvements in depressive symptoms, particularly with EPA-dominant formulas.
• Cognition: DHA supports brain volume preservation in older adults.
• Pregnancy: DHA supports fetal brain and visual development.

Large evidence base. REDUCE-IT (Bhatt 2019) is the strongest cardiovascular benefit trial, using prescription icosapent ethyl. STRENGTH and other mixed-EPA/DHA trials have been less consistent. Mozaffarian 2011 review summarises the cardiovascular evidence; Mocking 2016 covers depression.

General health: 1,000–2,000 mg combined EPA+DHA per day. Triglyceride reduction: 2,000–4,000 mg/day. Inflammatory or autoimmune conditions: 3,000+ mg/day under clinician guidance. Read the label carefully — a 1,000 mg fish oil capsule typically contains only 300–400 mg actual EPA+DHA, the rest is filler oil.

Fishy aftertaste or burps (refrigerate capsules to reduce; or switch to enteric-coated). GI upset on an empty stomach. Increased bleeding tendency at very high doses (>3 g/day). Theoretical bleeding risk with anticoagulants — clinically rarely an issue, but flag with your clinician.

Anticoagulants (warfarin, DOACs) — additive antiplatelet effect, monitor INR. Antihypertensives — modest additive blood-pressure lowering. Generally compatible with statins (often co-prescribed for residual triglyceride risk).