Fish And Shellfish - NHS

How much fish should we eat?

A healthy, balanced diet should include at least 2 portions of fish a week, including 1 of oily fish. Most of us aren't eating this much. A portion is around 140g (4.9oz).

However, for certain types of fish, there are recommendations about the maximum amount you should eat.

How much oily fish should I eat?

We should eat at least 1 portion (around 140g when cooked) of oily fish a week.

Oily fish usually have higher levels of pollutants than other types of seafood. For this reason, there are maximum recommendations for the number of portions some groups should be eating each week.

The following people should eat no more than 2 portions of oily fish a week:

• girls
• women who are planning a pregnancy or may have a child one day
• pregnant and breastfeeding women

This is because pollutants found in oily fish may build up in the body and affect the future development of a baby in the womb.

How much white fish should I eat?

You can safely eat as many portions of white fish per week as you like, except for the following, which may contain similar levels of certain pollutants as oily fish:

• sea bream
• sea bass
• turbot
• halibut
• rock salmon (also known as dogfish, flake, huss, rigg or rock eel)

Anyone who regularly eats a lot of fish should avoid eating these 5 fish, and brown meat from crabs, too often.

Even though shark and marlin are white fish, there is separate advice about how much of them you should eat:

• children, pregnant women and women who are trying to get pregnant should not eat shark, swordfish or marlin, because they contain more mercury than other fish
• other adults should have no more than 1 portion of shark, swordfish or marlin a week

Many shark and marlin species are endangered, so we should avoid eating these fish to help stop these species becoming extinct. See the sustainable fish and shellfish section below for more information. 

How much shellfish should I eat?

Although it is recommended that regular fish-eaters should avoid eating brown crab meat too often, there is no need to limit the amount of white crab meat that you eat. There are no maximum recommended amounts for other types of shellfish.

Eating fish while trying to get pregnant, and during pregnancy and breastfeeding

Eating fish is good for your health and the development of your baby. However, pregnant and breastfeeding women should avoid some types of fish and limit the amount they eat of some others. This is because of the levels of mercury and pollutants that some fish can contain.

When pregnant, you can reduce your risk of food poisoning by avoiding raw shellfish and making sure that any shellfish or smoked fish you eat is cooked thoroughly.

Below is advice from the Scientific Advisory Committee on Nutrition (SACN) and the Committee on Toxicity about eating fish when trying to get pregnant, or when pregnant or breastfeeding:

Shark, swordfish and marlin: do not eat these if you are pregnant or trying to get pregnant. All other adults, including breastfeeding women, should eat no more than 1 portion per week. This is because these fish can contain more mercury than other types of fish, and can damage a developing baby's nervous system.

Oily fish: all girls and women who haven’t been through the menopause yet, including those trying for a baby, or who are pregnant or breastfeeding, should have no more than 2 portions of oily fish a week. A portion is around 140g.

Tuna: if you are trying for a baby or are pregnant, you should have no more than 4 cans of tuna a week or no more than 2 tuna steaks a week. This is because tuna contains higher levels of mercury than other fish. If you are breastfeeding, there is no limit on how much tuna you can eat.

These figures are based on a medium-sized can of tuna with a drained weight of around 140g per can and a 140g cooked steak.

Remember, tuna doesn't count as oily fish. So if you've had a portion of tuna during the week, you can still have up to 2 portions (women) or 4 portions (men) of oily fish.

Unless your GP advises otherwise, avoid taking fish liver oil supplements when you're pregnant or trying for a baby. These are high in vitamin A (retinol), which can be harmful to your unborn baby. Pregnant women are advised to avoid taking supplements that contain vitamin A.

Learn more about having a healthy diet in pregnancy and foods to avoid in pregnancy.

Should children and babies over 6 months eat fish?

Children under the age of 16 should avoid eating any shark, swordfish or marlin. This is because the levels of mercury in these fish can affect a child's nervous system.

Avoid giving raw shellfish to babies and children to reduce their risk of getting food poisoning.

Learn more about healthy eating for the under-5s in Your baby's first solid foods.

You can give boys up to 4 portions of oily fish a week, but it is best to give girls no more than 2 portions a week. This is because the levels of pollutants that oily fish contain can build up in the body and may harm an unborn baby during a future pregnancy.