What is oily fish?

Oily fish refers to varieties that are high in poly-unsaturated fats called omega-3 fatty acids. Omega-3 fatty acids are considered essential because the body can only get them from food, we are unable to make them ourselves.


There are two main omega-3 fatty acids found in oily varieties of fish:

These differ to the omega-3 fats sourced from plants, such as those from flax and chia, because the short chain fats from plants need to be converted to the by the body and this process is quite inefficient.

Health benefits of oily fish include:

  1. May help protect against heart disease
  2. Offers nerve protection
  3. May protect joints
  4. May help support mental health
  5. May help reduce the risk of certain cancers
  6. Supports cognitive and motor development
  7. May reduce your child’s chances of developing asthma
  8. May protect your vision
  9. May reduce the risk of dementia for certain people
  10. May reduce the risk of auto-immune diseases

Discover the health benefits of apple cider vinegar, avocado and sea moss. Then check out some of our favourite fish recipes including peppered mackerel fish cakes and spicy sardine dip.

Salmon broccoli traybake

Types of oily fish

These are some of the better known varieties:

More like this
  • Salmon
  • Mackerel
  • Anchovies
  • Sardines
  • Trout
  • Herring

In 2018 the UK’s advice on what was deemed an oily variety of fish changed, and fresh tuna was removed as a source of omega-3 fatty acids, this is because levels of omega-3 fats in fresh tuna are now more comparable to those found in white varieties of fish. The advice regarding canned tuna has not changed, it continues to not count as an oily fish.

Health benefits of oily fish

1. May help protect against heart disease

Omega-3 fatty acid has been shown in numerous studies to help factors such as elevated cholesterol and high blood pressure, thereby reducing the risk of heart disease.

2. Offers nerve protection

Omega-3 fatty acid, especially DHA, is required for brain development and function and can offer neuroprotection against conditions such as Alzheimer's.

3. May protect joints

Omega-3 fatty acid has an anti-inflammatory action and has been shown in several studies to offer protection for joints, and may even help in the prevention of rheumatoid arthritis.

4. May help support mental health

Omega-3 fatty acid has often been shown to have a positive impact on mental health, including anxiety and depression.

5. May help reduce the risk of certain cancers

Eating oily fish appears to provide some protection against the risk of certain cancers, including colon, breast and prostate.

Masala mackerel and pickled onions on two plates

6. Supports cognitive and motor development

Eating oily fish, within the recommendations of dietary guidelines, during the last months of a pregnancy may have positive effects on your baby’s sensory, cognitive and motor development.

7. May reduce your child’s chances of developing asthma

Early introduction (before 43 weeks) of fish to an infant’s diet is associated with a lower risk of asthma.

8. May protect your vision

Researchers have revealed a link between dietary DHA and a lower risk of vision loss in older people.

9. May reduce dementia risk for certain people

One study on heart and brain health reported that the consumption of oily fish was associated with a reduced risk of dementia in those who had the APOE4 gene. This may be because the APOE protein helps carry cholesterol and other fats in the bloodstream, recent findings suggest that problems with the brain’s ability to process fats may play a role in Alzheimer’s and related conditions, including dementia.

10. May reduce the risk of autoimmune diseases

Eating oily fish has been linked to a reduced risk of type 1 diabetes and several other autoimmune conditions.

Tinned sardines

How much oily fish should we eat?

The NHS recommends that we include at least two portions (a portion being 140g cooked weight) of fish in our diet each week, one of which should be an oily variety.

For most people, eating more than one portion of oily fish a week is fine, but there are certain groups for which this is not recommended, this is because oily fish contain low levels of pollutants, like mercury, that can build up in the body.

Those who should limit their oily fish ( to no more than two portions per week) intake include:

  • Girls
  • Women planning a pregnancy
  • Pregnant and breastfeeding women

Try these oily fish recipes:

Masala mackerel
Spiced salmon & tomato traybake
Soy salmon & broccoli traybake
Grilled mackerel with soy, lime & ginger
Courgette & anchovy salad
Grilled harissa sardines with fennel & potato salad
Kipper fish cakes with watercress mayo
Tangy trout

Can you eat tuna when pregnant?

If you are trying for a baby or pregnant, the advice is to eat no more than four cans of tuna or no more than two tuna steaks* a week. This is because tuna contains higher levels of mercury than other fish. If you are breastfeeding, there is no limit to your tuna intake.

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

Should I be concerned about mercury levels in oily fish?

Sadly, nearly all fish and shellfish contain traces of mercury but it’s the larger fish that tend to contain the most. For many of us small amounts of mercury should not present a health problem but certain groups, such as pregnant and breastfeeding women, should keep their intake within recommended dietary limits.

Varieties of fish with lower levels of mercury include sardines and anchovies, whereas king mackerel or king fish is best avoided.

What about sustainability of oily fish?

Assessing the sustainability of fisheries is an ongoing process and subject to regular change. It is the Marine Stewardship Council (MSC) that certify seafood stocks after ascertaining that they may be fished at sustainable levels. This information is updated regularly so check that the fish you want to buy carries the familiar blue tick logo on the label.

The Marine Conservation Society also has a Good Fish Guide that is an easy reference to check current sustainability levels, this information is updated annually.

Enjoyed this? Now read…

How to eat fish sustainably
Health benefits of salmon
Are sardines healthy?
Best sources of omega-3

This article was reviewed on 20 December 2023 by Kerry Torrens.

Nicola Shubrook is a nutritional therapist and works with both private clients and the corporate sector. She is an accredited member of the British Association for Nutrition and Lifestyle Medicine (BANT) and the Complementary & Natural Healthcare Council (CNHC). Find out more at urbanwellness.co.uk.


All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.

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