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Fish and shellfish

A healthy, balanced diet should include at least 2 portions of fish a week, including 1 of oily fish.

That's because fish and shellfish are good sources of many vitamins and minerals. Oily fish – such as salmon and sardines – is also particularly high in long-chain omega-3 fatty acids, which can help to keep your heart healthy.

Most of us should have more fish in our diet, including more oily fish.

There is different advice for women who are pregnant or breastfeeding, and children and babies.

Fish that is steamed, baked or grilled is a healthier choice than fried fish. Frying can increase the fat content of fish and shellfish, especially if they’re cooked in batter.

Eating a wide variety of fish helps ensure there are enough fish to eat now and in the future. The Marine Stewardship Council has a guide to finding seafood from sustainable sources.

Types of fish

Different types of fish and shellfish provide different nutrients.

Oily fish

Oily fish include:

Fresh and canned tuna do not count as oily fish.

Oily fish are:

Some oily fish contain bones that you can eat. These include whitebait, canned sardines, pilchards and tinned salmon (but not fresh salmon). These fish can help keep our bones strong because they are sources of calcium and phosphorus.

White fish

Cod, haddock, plaice, pollock, coley, dab, flounder, red mullet, gurnard and tilapia are all examples of white fish. 

White fish are:

Shellfish

Shellfish includes prawns, mussels, scallops, squid and langoustine. 

Shellfish are:

Some types of shellfish, such as mussels, oysters, squid and crab, are also good sources of long-chain omega-3 fatty acids, but they do not contain as much as oily fish.

Oily fish and omega-3 fatty acids

Oily fish contains long-chain omega-3 fatty acids. Long-chain omega-3 can help to prevent heart disease. It is also important for women who are pregnant or breastfeeding, because it can help a baby's nervous system to develop.

Oily fish are the richest source of long-chain omega-3. Some white fish and shellfish also contain long-chain omega-3, but not as much as oily fish.

The main shellfish sources of long-chain omega-3 are:

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:

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:

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:

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.

Taking fish liver oil supplements

If you take fish liver oil supplements, remember that these are high in vitamin A. This is because fish store vitamin A in their livers. Having too much vitamin A over many years could be harmful.

The Scientific Advisory Committee on Nutrition advises that if you take supplements containing vitamin A, you should not have more than 1.5mg a day from your food and supplements combined. Pregnant women are advised to avoid taking supplements containing vitamin A, including fish liver oil supplements, as too much vitamin A can be harmful to an unborn baby. Learn more about vitamin A.

Eating sustainable fish and shellfish

When fish or shellfish are caught or produced in a way that allows stocks to replenish and that does not cause unnecessary damage to marine animals and plants, those fish or shellfish are called "sustainable". Seafish has information on responsible sourcing of seafood.

To ensure there are enough fish and shellfish to eat, choose from as wide a range of these foods as possible. If we eat only a few kinds of fish, then numbers of these fish can fall very low due to overfishing of these stocks.

Overfishing endangers the future supply of the fish and can also cause damage to the environment from which the fish is caught.

Fish and shellfish safety

Eating fish or shellfish that is not fresh or that has not been stored and prepared hygienically can cause food poisoning. In this section, you can find tips on how to store and prepare fish and shellfish.

Shellfish such as mussels, clams and oysters that are raw or not thoroughly cooked can contain harmful viruses and bacteria that can cause food poisoning. Thorough cooking usually kills any bacteria or viruses.

Most of the shellfish we eat is cooked first, but oysters are often served raw. 

Raw shellfish, particularly oysters, can contain low levels of certain viruses, such as norovirus. If you are serving oysters raw, be especially careful when buying and storing them.

Shellfish can also contain toxins.

Depending on the type of toxin present, the symptoms from eating contaminated shellfish may include: 

These toxins do not break down during cooking.

The Food Standards Agency (FSA) advises that older people, pregnant women, very young children and people who have a weakened immune system should avoid eating raw or lightly cooked shellfish to reduce their risk of getting food poisoning.

Pregnant women should only eat smoked fish products that have been thoroughly cooked.

Catching fish and shellfish

If you want to take shellfish from any public waters, it's important that you check local notices or with your local authority that the area isn't closed to fishing.

Visit GOV.UK to find your local authority.

If an area of public water is closed, it may be for public health reasons, such as high toxin or bacterial or chemical contamination. In this case it would be dangerous to eat shellfish from that area.

Buying fish and shellfish

When choosing fish and shellfish, remember:

Storing fish and shellfish

Follow these hygiene tips when storing fish:

Preparing fish and shellfish

Follow these hygiene tips when preparing fish:

Fish and shellfish allergy

Allergies to fish or shellfish are quite common and can cause severe reactions.

People who are allergic to one type of fish often react to other types. Similarly, people who are allergic to one type of shellfish, such as prawns, crabs, mussels or scallops, often react to other types.

Cooking fish or shellfish doesn't make someone with a fish or shellfish allergy less likely to have a bad reaction.

Learn more about food allergies.