"Get more omega-3s" is one of the most repeated pieces of nutrition advice — and one of the most misunderstood. The problem is that the word "omega-3" covers three different fats, and only two of them do most of the work your body cares about. Fish happens to be the richest natural source of exactly those two.
The three omega-3s, briefly
- ALA (alpha-linolenic acid) — the plant form, found in flaxseed, chia, and walnuts. It's essential, but your body has to convert it into the usable forms.
- EPA (eicosapentaenoic acid) — the anti-inflammatory workhorse, found in fish.
- DHA (docosahexaenoic acid) — a core structural fat in your brain, eyes, and nerves, also found in fish.
Here's the catch that most "add flaxseed to your smoothie" advice glosses over: humans convert ALA to EPA at roughly 5–10%, and to DHA at under 1%. So while plant sources are healthy, they're a wildly inefficient way to raise the omega-3 levels that actually matter. Marine sources hand you EPA and DHA directly.
The highest omega-3 fish, ranked
The table below shows combined EPA + DHA per 100g serving. Anything above roughly 1 gram is an excellent source.
| Fish | Omega-3 (EPA+DHA) per 100g | Notes |
|---|---|---|
| Mackerel (Atlantic) | 2.6 g | Highest, and cheap |
| Salmon (farmed) | 2.3 g | Reliable, widely available |
| Herring | 2.0 g | Underrated, sustainable |
| Sardines | 1.5 g | Cheap, low-mercury |
| Anchovies | 1.4 g | Big flavour in small amounts |
| Trout (rainbow) | 1.0 g | Mild, easy to cook |
| Tuna (canned, light) | 0.3 g | Convenient but lower |
The pattern is clear: small, cold-water, oily fish punch far above their weight. Mackerel, sardines, and herring are cheaper than salmon and, gram for gram, at least as good.
How much do you actually need?
Major health bodies converge on a simple target:
- General heart health: two servings of oily fish per week (~250–500 mg EPA+DHA per day averaged out).
- Elevated triglycerides: higher intakes of 2–4 g per day, usually under medical supervision.
Two servings of the fish above easily clears the general target. You don't need to count milligrams — you need to eat oily fish twice a week.
What omega-3s do for you
The evidence base here is unusually deep. Regular EPA/DHA intake is associated with:
- Lower triglycerides and modestly improved blood pressure.
- Reduced risk of dying from heart disease — the effect that drives official recommendations.
- Anti-inflammatory effects relevant to joint and metabolic health.
- Support for brain and eye development, which is why DHA is added to infant formula.
Do you need a fish oil supplement?
If you eat oily fish twice a week, probably not — whole fish also delivers protein, selenium, vitamin D, and B12 that a capsule doesn't. Supplements make sense mainly for people who won't or can't eat fish, or who need therapeutic doses. If you do supplement, look for a product that lists the actual EPA and DHA amounts, not just "fish oil 1000mg."
The bottom line
Omega-3s are one of the best-supported nutrients in all of nutrition science, and fish is simply the most efficient way to get the forms that count. Skip the mental math: eat mackerel, sardines, herring, or salmon twice a week and you've covered it.