Salmon and oily fish: the omega-3 in a real portion

Salmon is expensive, sardines cost almost nothing, and both sit under the same label at the counter. The question worth asking is what you get back for the money: how much protein, how much omega-3, and how often it is actually worth eating.

The answer is less complicated than the shelf makes it look. One or two portions of oily fish a week covers the reason people eat it in the first place, and the gap between the priciest and the cheapest option on the plate is far smaller than the gap on the receipt.

What a portion actually gives you

These are rounded averages per 100 g of cooked fish, and they move with the cooking method. Dry roasting concentrates everything as water evaporates, pan-frying in oil adds 5–10 g of fat per portion, and tinned fish depends entirely on whether it sits in oil or in water.

• Farmed salmon: roughly 210 kcal, 22 g protein, 13 g fat, of which 1.5–2 g is EPA and DHA.
• Wild salmon: roughly 160 kcal, 24 g protein, 7 g fat, around 1–1.5 g EPA and DHA.
• Mackerel: roughly 230 kcal, 22 g protein, 15 g fat, 2–2.5 g EPA and DHA — the most omega-3 per pound spent.
• Tinned sardines, drained: roughly 200 kcal, 24 g protein, 11 g fat, around 1.5 g EPA and DHA, plus about 300 mg of calcium because you eat the bones.
• Trout: roughly 150 kcal, 21 g protein, 6 g fat, around 1 g EPA and DHA.
• Tinned tuna in water: roughly 115 kcal, 25 g protein, 1 g fat — but only about 0.3 g of EPA and DHA.

Fibre is zero, in every fish, without exception. That is the first thing a fish meal needs alongside it: vegetables, pulses or a wholegrain.

Nobody weighs out 100 g in real life. Supermarket salmon fillets usually run 140–180 g raw and lose a fifth to a quarter of that weight in the oven, so one fillet lands at roughly 25–30 g of protein and 2–3 g of omega-3. A 120 g tin of sardines, drained, gives about 20 g of protein and 1.5 g of omega-3.

Fitting it into the week

General guidance settles around 250–500 mg of EPA and DHA a day, which is 2–3.5 g across a week. One portion of salmon or mackerel nearly covers that on its own; two puts you comfortably clear. There is no prize for eating it daily.

If you train and you are aiming for 1.6–2.2 g of protein per kilo of bodyweight, fish is one meal in that arithmetic rather than the whole plan. Eggs, yoghurt, chicken and pulses still do the heavy lifting — a five-minute breakfast with 30 g of protein handles the start of the day, and chicken covers most evenings.

A workable pattern: salmon or mackerel once for dinner, sardines or tuna once at lunch, chicken or eggs the rest of the time. A tin of sardines slots straight into a bulgur salad that survives until lunchtime in place of the chicken, and on the nights you fancy something else there is always yoghurt-marinated chicken skewers.

Who it suits, and who it doesn't

Oily fish works well if you eat at maintenance or slightly above, if you want protein that isn't dry, and if your vitamin D runs thin over winter — oily fish is one of very few foods that carries any meaningful amount.

It suits you less if you are in a hard deficit counting every calorie. Salmon carries roughly twice the calories per gram of protein that white fish or tuna in water does. That is not a flaw in the food, just a question of where it fits.

Skip it entirely with a fish or shellfish allergy. Sardines and mackerel are also high in purines, so anyone with gout should raise it with their doctor. And if you simply cannot stand fish, algae oil supplies the same EPA and DHA — it is the one plant source that does, while flaxseed and walnuts give ALA, which the body converts poorly.

Combinations that take no effort

• Salmon fillet, 12–14 minutes at 200 °C, with potatoes and a green salad.
• Tinned sardines on wholemeal toast with lemon and red onion — three minutes, about 25 g of protein.
• Mackerel in a dry pan, served with beans or chickpeas so the meal has some fibre in it.
• Tuna in water mixed with yoghurt instead of mayonnaise, plus sweetcorn and tomato.
• Yesterday's cold salmon flaked through pasta, on the same principle as this baked pasta with broccoli and chicken.

Myths worth dropping

"Tinned fish is a poor substitute." It isn't. Tinned sardines and mackerel hold onto their omega-3 and match fresh fish on protein, at a fraction of the price.

"Tuna counts as oily fish." Tinned tuna in water is an excellent protein source but carries very little EPA and DHA. If omega-3 is the point, it is not a stand-in for salmon or mackerel.

"Farmed salmon is worthless." Farmed salmon actually delivers slightly more total omega-3 per portion than wild, because it is fattier. The fatty acid profile differs, but you lose nothing in grams of EPA and DHA on the plate.

"Smoked salmon is the same thing." Nutritionally it is close, but it carries around 3 g of salt per 100 g and the portions are small — 50 g of smoked salmon is about 10 g of protein, not 25.

"Fish oil capsules do the same job." They supply the fatty acids but not the protein, iodine, selenium or vitamin D that come with the fish. The evidence is strongest for eating fish regularly, not for treating a capsule as a replacement.

When to see a doctor

Ask before taking fish oil in larger doses if you are on blood-thinning medication. Pregnancy comes with specific advice about large predatory fish and mercury — salmon, sardines, mackerel and trout sit at the low end, but follow the guidance your own doctor gives you. Any allergic reaction to fish involving swelling or difficulty breathing needs emergency care.

The short version

A 120–150 g portion of oily fish gives you roughly 25–30 g of protein, 2–3 g of omega-3 and no fibre at all. Two portions a week is enough. Sardines and mackerel deliver nearly what salmon does for far less money, and tuna in water is a protein meal rather than an omega-3 one. The rest is detail.