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Fish oils

Fish oils classification

Fish body oil and fish liver oil are rich in omega-3 essential fatty acids, which can help control your immune system and fight joint inflammation. Fish liver oil is also a rich source of vitamin A (a strong antioxidant) and vitamin D (which is important for maintaining healthy joints)

Evidence suggests that fish body oil can improve the symptoms of rheumatoid arthritis. Unconfirmed evidence also suggests a combination of fish body and liver oils might also be useful in the long term, particularly in reducing the use of non-steroidal anti-inflammatory drugs (NSAIDs). There isn’t enough evidence for the use of fish liver oil for osteoarthritis.

What is it?

Family: Nutritional supplement
Scientific name: Fish oil (fish body oil and/or fish liver oil)

Fish body oil is made from tissues of fatty fish like sardines, sprat, salmon, and mackerel. Fish liver oil is made by pressing the cooked liver of halibut, shark or, most commonly, cod. Both types are available from high-street retailers and over the internet.

How does it work?

Fish oils are rich in omega-3 essential fatty acids, which have strong anti-inflammatory properties:

  • They significantly reduce the release of several elements that play a part in inflammation from your white blood cells.
  • They form the building blocks for prostaglandins, which regulate your immune system and fight joint inflammation.

Omega-3 fatty acids also play a role in lowering cholesterol and triglyceride levels in your blood, so they can reduce the risk of heart disease and stroke in people with inflammatory arthritis.

Fish liver oil contains high levels of vitamins A and D. Vitamin A is a strong antioxidant (meaning it can prevent cell damage in your body by interacting with harmful molecules called free radicals which are produced within the cells). Vitamin D plays an important part in the production of proteoglycan in cartilage as well as helping to maintain a healthy musculoskeletal system.

Is it safe?

In the UK, dietary guidelines recommend eating two portions of fish a week, including one oily. This works out at about 0.45 g per day of omega-3 fatty acids. Fish oil is considered to be well tolerated at this dose. However, certain environmental chemicals such as methylmercury and polychlorinated biphenyls (PCBs) can contaminate fish supplies and there’s a concern that taking very high doses of fish oil can cause a build-up of these chemicals in the body. This is also a concern for people who eat fish frequently.

At the correct doses, side-effects are usually minor and uncommon. The most common is stomach upsets, but flatulence and diarrhoea may also be experienced. You shouldn’t use fish oil if you take anticoagulants because fish oil can interfere with blood clotting.

It’s important not to take large amounts of fish liver oil because it can give you more than the recommended dietary allowance of vitamin A. Taking too much vitamin A can lead to liver problems and hair loss. It may also harm unborn babies, so you should avoid fish liver oil and vitamin A supplements if you’re pregnant. Fish liver oil that hasn’t been well purified can contain some contaminants (like mercury, and dioxins), which can lead to health problems, but most supplement companies test fish liver oil for purity before it become publicly available.


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