There is good evidence that eating them reduces the risk of death from heart disease. They are a good source of omega 3 polyunsaturated fatty acids. White fish also contain these fatty acids, but at much lower levels than in oily fish.

Omega 3 fatty acids are important for the development of the central nervous system in babies, before and after they are born. There is some evidence suggesting that if women eat oily fish when they are pregnant and when breastfeeding this helps their baby’s development.

Everyone should eat at least two portions of fish a week, including one portion of oily fish. A portion is 140g.

What are oily fish?

Oily fish include salmon, trout, mackerel, sardines, pilchards, herring, kipper, eel and whitebait. These fish count as oily fish whether they're canned, fresh or frozen.

Fresh tuna is an oily fish but canned tuna doesn’t count as oily. This is because when it's canned the fats are reduced to levels similar to white fish. So, canned tuna is a healthy choice for most people, but it doesn't have the same benefits as eating oily fish.

Can I eat as much oily fish as I like?

Even though eating oily fish has a number of benefits, there are limits to the amount we should eat.

Girls and women who might have a baby one day shouldn’t eat more than two portions of oily fish a week. A portion is 140g. In general, this advice also applies to women who are pregnant or breastfeeding.

Women who aren’t going to get pregnant in the future, boys and men can eat up to four portions a week.

Why should I limit the amount of oily fish I eat?

Because they can contain dioxins and polychlorinated biphenyls (PCBs).

Dioxins are a type of pollutant found in fish. They are by-products from a number of industrial processes and household fires. They are found throughout the environment and are found in fish.

PCBs are another type of pollutant, which were used mainly in electrical equipment. But PCBs haven’t been manufactured since the 1970s and they are no longer permitted in the UK.

Levels of both dioxins and PCBs are falling in the environment and the food we eat.

Dioxins and PCBs will not have an immediate effect on your health. Any risk comes from taking in high levels over a long period of time.

Is the advice on eating farmed salmon different to other types of oily fish?

No, the advice on farmed salmon is the same – that is that girls or women who might have a baby one day and women who are pregnant or breastfeeding shouldn’t eat more than two portions a week. Women who aren’t going to get pregnant in the future, boys and men can eat up to four portions a week. Remember that if you are eating this much salmon in a week, you shouldn’t eat other types of oily fish as well.

Should I eat oily fish when I’m pregnant or breastfeeding?

Yes, this could help your baby’s development.

In general, the advice for pregnant and breastfeeding women is the same as for girls and women who might have a baby one day – that is that you shouldn’t eat more than two portions of oily fish a week.

When you’re pregnant, or planning to get pregnant, you should eat no more than four medium-size cans of tuna a week (with a drained weight of about 140g per can), or two fresh tuna steaks (weighing about 140g when cooked or 170g raw).

Remember that fresh tuna is oily fish, so if you eat two fresh tuna steaks in one week, you shouldn’t eat any other oily fish that week. Tinned tuna doesn’t count as oily fish, so you can eat this on top of the maximum of two portions of oily fish (as long as it’s not fresh tuna or swordfish), but remember not to eat more than four medium-sized cans a week.

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