How much omega-3 should I take a day?

General guidance is about 250–500 mg of combined EPA and DHA daily for healthy adults, which two servings of oily fish a week roughly provides. Higher doses of 2–4 g are used clinically for elevated triglycerides, under medical supervision.

Do flax and chia give you the same omega-3 as fish?

No. They provide ALA, which the body converts to EPA at under 10% and to DHA at under 1%. They are worth eating, but they are not a substitute for EPA and DHA if that is what you are aiming for.

Is algae oil as good as fish oil?

Yes, and it is the original source, fish accumulate EPA and DHA by eating algae. Algae oil supplements provide both directly, are suitable for vegans, and carry no mercury concern.

Omega-3: how much EPA and DHA you actually need

The conversion from plant omega-3 to the forms your body uses runs at a few percent. Which makes the plant sources far less interchangeable with fish than the labels suggest.

The AIM teamNovember 13, 20264 min read

"Omega-3" on a label covers three different molecules that are not interchangeable, and the difference between them is the whole practical story.

The three forms

ALA (alpha-linolenic acid): from flaxseed, chia, walnuts, hemp, canola. The plant form.

EPA (eicosapentaenoic acid): from oily fish and algae. Most of the cardiovascular and anti-inflammatory evidence involves this one.

DHA (docosahexaenoic acid): from oily fish and algae. Structural, concentrated in brain and retina, and the one that matters most in pregnancy and infant development.

The conversion problem

The body can convert ALA into EPA and DHA. It does so badly.

ALA → EPA: under 10%: often around 5%
ALA → DHA: under 1%

Which means a tablespoon of flaxseed listing 2,400 mg of omega-3 delivers on the order of 120 mg of EPA and perhaps 10–20 mg of DHA.

Conversion is worse in men than women, and worse on a diet high in linoleic acid, because both use the same enzymes.

This is why "high in omega-3" on a plant product tells you very little about whether it does what you are buying it for.

The targets

General health: about 250–500 mg combined EPA and DHA daily.
Pregnancy and breastfeeding: at least 200–300 mg DHA specifically.
Elevated triglycerides: 2–4 g daily, which is a clinical dose and a conversation with a doctor rather than a shelf decision.

Two servings of oily fish a week covers the general figure comfortably.

Where to get it

Fish, per 3 oz cooked:

Fish	EPA + DHA
Salmon, farmed	1,800 mg
Salmon, wild	1,200 mg
Sardines	1,000 mg
Mackerel (Atlantic)	1,000 mg
Herring	1,700 mg
Anchovies	950 mg
Canned light tuna	230 mg

All of those are on the low-mercury list from the fish article, which is convenient, the highest omega-3 fish are mostly small, and small means low mercury.

Algae oil is the vegan option and it is the original source: fish get their EPA and DHA by eating algae. Supplements provide both directly, with no conversion step and no mercury question.

Fish oil works. Look for the actual EPA and DHA figures on the back rather than the total omega-3 number on the front, a 1,000 mg capsule frequently contains only around 300 mg of the two that matter.

What the evidence supports

Strongest: lowering triglycerides: at the higher clinical doses.

Reasonable: cardiovascular outcomes in people with existing heart disease, though large trials in healthy populations have been mixed and the picture is less clean than it looked a decade ago.

Reasonable: DHA in pregnancy for fetal brain and eye development.

Weaker than marketed: general cognitive benefit in healthy adults, joint pain, mood. Some signal, not settled.

Practically

Eat oily fish twice a week and you need to think about none of this. If you do not eat fish, algae oil is the clean answer. If you rely on flax and chia, keep eating them, they are good foods, but do not count their omega-3 figure as if it were the same nutrient.

Common questions

How much omega-3 should I take a day?: General guidance is about 250–500 mg of combined EPA and DHA daily for healthy adults, which two servings of oily fish a week roughly provides. Higher doses of 2–4 g are used clinically for elevated triglycerides, under medical supervision.
Do flax and chia give you the same omega-3 as fish?: No. They provide ALA, which the body converts to EPA at under 10% and to DHA at under 1%. They are worth eating, but they are not a substitute for EPA and DHA if that is what you are aiming for.
Is algae oil as good as fish oil?: Yes, and it is the original source, fish accumulate EPA and DHA by eating algae. Algae oil supplements provide both directly, are suitable for vegans, and carry no mercury concern.