A healthy diet should include at least two portions of fish a week, including one of oily fish.
That's because fish are good sources of many vitamins and minerals. Oily fish – such as salmon and fresh tuna – is also particularly high in long-chain omega-3 fatty acids, which may help to keep your heart healthy.
Most of us should have more fish in our diet, including more oily fish. However, there are maximum recommended amounts for oily fish and some types of white fish. There is additional advice for women who are pregnant or breastfeeding, 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, especially if they’re cooked in batter.
To ensure there are enough fish to eat now and in the future, we should try to eat a wide variety of fish and to buy fish from sustainable sources.
Click on the links below for more information about incorporating fish into your diet.
Types of fish
Different types of fish provide different nutrients.
Salmon, mackerel, sardines, trout and herring are all examples of oily fish. Oily fish are:
- High in long-chain omega-3 fatty acids, which may help to prevent heart disease
- A good source of vitamin D.
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 good sources of calcium and phosphorus.
Which fish are oily fish?
These fish are all oily fish, meaning they are good sources of long-chain omega-3:
- Herring (bloater, kipper and hilsa are types of herring)
- Jack (also known as scad, horse mackerel and trevally)
- Tuna (fresh)
Canned tuna does not count as oily fish. Fresh tuna is an oily fish, but when it is canned the amount of long-chain omega-3 fatty acids is reduced to levels similar to those in other white fish.
Cod, haddock, plaice, lemon sole, pollock, coley, dab, flounder, red mullet, gurnard and tilapia are all examples of white fish.
White fish are:
- Low in fat, making them one of the healthier, low-fat alternatives to red or processed meat, which tends to be higher in fat, especially saturated fat
- Asource of omega-3 fatty acids, but at much lower levels than oily fish
Oily fish and omega-3 fatty acids
Oily fish contains a special kind of fat, called long-chain omega-3 fatty acids.
Long-chain omega-3 may 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.
How much fish should we eat?
A healthy diet should include at least two portions of fish a week, including one 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 one portion (around 140g when cooked) of oily fish a week.
Oily fish can contain low levels of pollutants that can build up in the body. For this reason, there are maximum recommendations for the number of portions we should be eating each week. These recommendations are different for different groups of people:
- The general population is advised to have no more than four portions of oily fish a week.
- Women who are planning a pregnancy or who are currently pregnant or breastfeeding should eat no more than two portions of oily fish a week. This is because pollutants found in oily fish may affect the future development of a baby in the womb.
- Children, pregnant women and women who are trying to get pregnant should not eat swordfish, as it contains more mercury than other fish. Other adults are advised to eat no more than one portion of swordfish per week.
How much white fish should I eat?
You can safely eat as many portions of white fish per week as you like.
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 or marlin. This is because they contain more mercury than other fish.
- Other adults should have no more than one portion of shark or marlin per 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 section below for more information.
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 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 fish and making sure that any fish you eat is cooked thoroughly.
Below is advice from the Scientific Advisory Committee on Nutrition 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 one 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: if you are trying for a baby, or are pregnant or breastfeeding, you should have no more than two portions of oily fish a week. A portion is around 140g.
- Canned tuna: if you are trying for a baby or are pregnant, you should have no more than four cans of tuna 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 canned tuna you can eat.
These figures are based on a medium-sized can of tuna with a drained weight of around 140g per can.
Remember, canned tuna doesn't count as oily fish. So if you’ve had a portion of canned tuna during the week, you can still have up to two portions of oily fish.
Due to the higher levels of mercury in tuna, if you’re eating canned tuna, don’t pick fresh tuna as your 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.
Should children and babies over six 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 fish to babies and children to reduce their risk of getting food poisoning.
You can give boys up to four portions of oily fish a week, but it is best to give girls no more than two portions a week. This is because the low 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.
Eating sustainable fish
When fish 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".
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.
Learn more about sustainable fish and shellfish, and what you can do to help from GOV.UK: protecting and sustainably using the marine environment.
When choosing fish, remember:
- Buy fish and shellfish from reputable sources.
- Choose fresh fish that is refrigerated, kept on ice or frozen.
- Don't buy cooked or ready-to-eat fish that is touching raw fish or shellfish.
- When shopping, pick up fish last and take it straight home. Fish can go off very quickly once out of the fridge especially if exposed to high cyclic temperatures.
- Where possible, buy fish from sustainable sources.
Follow these hygiene tips when storing fish:
- Put fish in the fridge or freezer as soon as you get home.
- Make sure that all fish are in covered containers.
- Don't store fish in water.
Follow these hygiene tips when preparing fish:
- Wash your hands thoroughly before and after handling fish.
- Don't allow raw fish to come into contact with cooked or ready-to-eat food.
- Use separate plates and utensils for preparing raw fish and other food.
- Thaw fish in the fridge overnight. If you need to thaw it more quickly, you could use a microwave. Use the "defrost" setting and stop when the fish is icy, but flexible.
- If you’re marinating seafood, put it in the fridge and throw the marinade away after removing the raw fish. If you want to use the marinade as a dip or sauce, set some aside before it touches the raw fish.
Allergies to fish are quite common and can cause severe reactions.
People who are allergic to one type of fish often react to other types.
Cooking fish doesn't make someone with a fish allergy less likely to have a bad reaction.