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Alzheimer's disease health centre

Omega 3 fish oil

BMJ Group Medical Reference


This information is for people with dementia and their carers. It tells you about omega 3 fish oil, a treatment that has been tried for dementia. It's based on the best and most up-to-date research.

Does it work?

We don't know. There hasn't been much research on fish oil as a treatment for dementia. The little that has been done suggests that fish oil doesn't work, but we can't know for sure without more research.

What is it?

Fish such as trout, mackerel, sardines, and salmon have a lot of oil in them. You can get oil from these fish as capsules. Fish oil contains substances called omega-3 fatty acids.

You can buy fish oil capsules over the counter from pharmacies, health food shops, or supermarkets.


There's not enough research yet to say whether fish oil can help people with dementia. So far, studies have found no difference in symptoms between people who took fish oil and people who took a dummy treatment (a placebo). [163]

How does it work?

It's not clear whether fish oil does work for people with dementia. We know that omega 3 fish oils can change the balance of some fats in the blood. They can also reduce inflammation. If fish oil does turn out to work for people with dementia, it may be because of one of these effects. [164]


In studies looking at people with dementia, fish oil was a safe treatment. People who took it didn't get any serious problems. But some people got diarrhoea, or pain when they were eating. [164]

Other studies looking at fish oil supplements have found that they can cause wind, bad breath, and an unpleasant fishy taste in the mouth. [165]

How good is the research?

There is very little research on fish oil as a treatment for dementia.

We found one good-quality study (a randomised controlled trial). In the trial, 174 people with mild to moderate Alzheimer's disease were given either omega 3 fish oil or a dummy treatment (a placebo) for six months. There was no difference in the symptoms of dementia between the people who got fish oil and people who got the placebo.



A placebo is a 'pretend' or dummy treatment that contains no active substances. A placebo is often given to half the people taking part in medical research trials, for comparison with the 'real' treatment. It is made to look and taste identical to the drug treatment being tested, so that people in the studies do not know if they are getting the placebo or the 'real' treatment. Researchers often talk about the 'placebo effect'. This is where patients feel better after having a placebo treatment because they expect to feel better. Tests may indicate that they actually are better. In the same way, people can also get side effects after having a placebo treatment. Drug treatments can also have a 'placebo effect'. This is why, to get a true picture of how well a drug works, it is important to compare it against a placebo treatment.

randomised controlled trials

Randomised controlled trials are medical studies designed to test whether a treatment works. Patients are split into groups. One group is given the treatment being tested (for example, an antidepressant drug) while another group (called the comparison or control group) is given an alternative treatment. This could be a different type of drug or a dummy treatment (a placebo). Researchers then compare the effects of the different treatments.

For more terms related to Dementia


For references related to Dementia click here.
Last Updated: August 15, 2013
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.

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