Omega-3s: Why They Matter and How to Get Them

Omega-3s are polyunsaturated fats that your body uses structurally, not just for fuel. DHA in particular is a major building block of the brain and the retina of the eye, which is why it matters so much in pregnancy and early life. EPA and DHA together influence how your blood vessels behave, help keep triglyceride levels in check, and support normal heart rhythm.

The heart is where the evidence is strongest. The American Heart Association's review of seafood and long-chain omega-3s concluded that eating oily fish is linked to a lower risk of heart problems, which is why the standard advice lands on a couple of servings a week. This is not a fringe supplement claim, it is mainstream cardiology. One of the two omega-3 families is also essential, meaning your body cannot make it at all and it has to come from food.

There are three omega-3s worth knowing by name. Getting them straight is what separates people who think they are covered from people who actually are.

• ALA (alpha-linolenic acid), the plant form, found in flaxseed, chia, walnuts, and rapeseed oil. This is the essential one your body cannot make.
• EPA (eicosapentaenoic acid), a long-chain form found mainly in oily fish and algae, active in heart and inflammatory signalling.
• DHA (docosahexaenoic acid), the other long-chain form, concentrated in the brain and eyes, also from oily fish and algae.

In theory your body can convert ALA into EPA and DHA. In practice it does this poorly. Tracer studies find that conversion of ALA to EPA is typically under 10 percent, and conversion all the way to DHA is often just a few percent, sometimes barely measurable, especially in men. Women tend to convert somewhat better, likely due to oestrogen. The upshot is that eating flaxseed alone does not reliably deliver the EPA and DHA your heart and brain use most. You get plenty of the raw material and only a trickle of the finished product.

For general health, European food-safety guidance sets an adequate intake of about 250 milligrams of combined EPA and DHA per day for adults. That is a modest amount, and the easiest way to reach it is roughly two servings of oily fish a week, such as salmon, sardines, mackerel, or herring. One good salmon fillet can cover several days' worth on its own.

You do not need to megadose. Very high doses of fish oil are sometimes used medically to lower high triglycerides, but that is a treatment decision for a doctor, not a general recommendation. For most people, hitting the modest daily target consistently matters far more than the size of any single dose.

If you eat fish

This is the simple path. Two servings of oily fish a week gets you comfortably past the target with room to spare. Tinned sardines, mackerel, and salmon are cheap, keep for ages, and count exactly the same as fresh. If you dislike the strong-tasting fish, milder salmon or a fish oil supplement fills the gap.

If you eat plant based

You can absolutely cover omega-3 without fish, you just do it in two parts. First, get ALA daily from ground flaxseed, chia seeds, walnuts, or rapeseed oil, which is easy and cheap. Second, because conversion to EPA and DHA is weak, add a direct source of the long-chain forms through an algae-based (algal) supplement. Algae is where fish get their omega-3 in the first place, so you are simply going to the original source. This gives a plant-based diet the same EPA and DHA a fish eater gets, no compromise involved.