Not all omega-3s are the same
Omega-3s come in two practical groups [1]:
- EPA and DHA — the long-chain omega-3s most studied for heart and brain health, found mainly in fatty fish and algae.
- ALA — a shorter plant omega-3 found in flaxseed, chia, walnuts, and canola/soybean oils.
The conversion catch
The body can convert ALA into EPA and DHA, but the conversion is very limited — reported at less than about 15%, and the step to DHA is even smaller [1]. So eating flax and chia provides ALA and its own benefits, but it's an inefficient way to raise EPA and DHA specifically.
Best food sources
- EPA/DHA: salmon, mackerel, herring, sardines, anchovies, and trout. Two servings of fatty fish a week is a common guideline.
- ALA: ground flaxseed, chia seeds, walnuts, and canola or soybean oil.
- Vegan EPA/DHA: algae (algal oil) is the plant-based source of the long-chain omega-3s (see [omega-3 formats](/learn/omega-3-formats-algae-guide)).
How much
There's no separate RDA for EPA/DHA, but the Adequate Intake for ALA is 1.6 g/day for men and 1.1 g/day for women [1]. General guidance favors regular fatty fish for EPA and DHA.
Food vs. supplement
For most people, eating fatty fish a couple of times a week is the simplest way to get EPA and DHA — with protein and other nutrients along for the ride. A fish oil or algae supplement is a reasonable alternative for those who don't eat fish, but high-dose fish oil can affect bleeding (see fish oil safety).
Practical guidance
- Eat fatty fish regularly for EPA and DHA; use algae oil if you're vegan or vegetarian.
- Don't rely on flax/chia alone to raise EPA and DHA — they mainly provide ALA.
- Consider a supplement only to fill a gap, and watch the dose if you're on blood thinners or facing surgery.