EPA vs DHA: Understanding the Two Key Omega-3s

Fish-oil labels are a small masterpiece of misdirection: total fish oil, omega-3, EPA, DHA, all printed in sizes chosen to flatter the largest number. The two that actually matter are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Learn to find them and most of the category's marketing quietly loses its power over you.

What EPA and DHA are

EPA and DHA are the two long-chain omega-3 fatty acids found mainly in oily fish and algae. They're often lumped together with ALA (alpha-linolenic acid), the plant omega-3 in flax and walnuts — but ALA is a different, shorter molecule, and the body converts only a small fraction of it into EPA and less still into DHA. That's why fish or algal oil is the direct route, and why "contains omega-3 from flax" is not the same promise as a meaningful EPA/DHA dose.

The authorized roles

Under EFSA, EPA and DHA contribute to the normal function of the heart, at a daily intake of 250 mg. DHA contributes to the maintenance of normal brain function and to the maintenance of normal vision, also at 250 mg per day. These are established structure/function roles — not claims to treat or prevent disease.

At higher intakes, EFSA also recognises that DHA and EPA contribute to the maintenance of normal blood pressure (from about 3 g per day) and to the maintenance of normal blood triglyceride levels (from about 2 g per day). These are worded around maintaining normal levels in the general population, and the higher-dose claims come with a ceiling: EFSA advises supplemental EPA + DHA generally stay at or below about 5 g per day. They are not claims that fish oil lowers blood pressure or cholesterol as a treatment. There's also a role in early life — maternal DHA intake contributes to the normal brain and eye development of the foetus and breastfed infants, under specific conditions — relevant if you're pregnant or nursing.

Decode the label

"1,000 mg fish oil" is not "1,000 mg omega-3"

How to read the label

The single most useful habit: find the combined EPA + DHA figure and treat everything else as decoration. A capsule can weigh a gram and still deliver only a couple of hundred milligrams of the actives.

• Check EPA + DHA, not total fish oil. Add the two milligram figures.
• Match to your goal — 250 mg/day covers the heart and (for DHA) brain and vision roles; the blood-pressure and triglyceride roles need substantially higher, deliberate intakes.
• Purity matters — look for oil tested for heavy metals and low oxidation (a low "TOTOX" value). Strongly fishy oil is a sign of poor handling.
• Form — triglyceride and ethyl-ester forms both work; concentration, purity, and consistent dosing matter more than the form name.

How much and how to take it

For the everyday heart, brain, and vision roles, 250 mg of combined EPA + DHA per day is the reference — roughly two servings of oily fish a week for most people. Supplements are a practical top-up if your diet is low in fish. Take omega-3 with a meal containing some fat, keep it consistent, and store it cool and sealed to slow oxidation. If you're aiming at the higher intakes tied to the blood-pressure or triglyceride roles, or you take blood-thinning medication, talk to your doctor first.

Vegetarian and vegan options

If you don't eat fish, you have two routes. The direct one is algal oil — omega-3s are originally made by microalgae (fish get theirs by eating algae), so an algal supplement supplies DHA, and increasingly EPA, without the fish. The indirect route, relying on ALA from flax, chia, or walnuts, is far less efficient, since the body converts only a small percentage of ALA to EPA and very little to DHA. Plant oils are worth eating, but they're not a reliable substitute for a direct EPA/DHA source. Check any plant product for an actual EPA + DHA figure rather than a general "omega-3" claim resting on ALA. Algal oil also sidesteps two things fish oil is prone to — the sustainability questions around sourcing and the oxidation that gives cheap fish oil its off smell — which is worth weighing even if you do eat fish.

Where it fits

You can see Agen's omega-3 fish oil, or the broader heart & circulation range. If brain support is your main interest, our guide to supplements for focus and concentration puts DHA alongside the other nutrients with authorized cognitive roles.

The bottom line

Aim for a meaningful combined EPA + DHA dose from a clean, tested oil, and read the label for that figure rather than the total oil weight. The omega-3s have well-established roles in normal heart, brain, and vision function at 250 mg/day, with additional authorized roles at higher, deliberate intakes. Match the dose to your goal, keep it consistent, and check with your doctor if you're on medication or pregnant.