Omega-3

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1 smiley: This treatment is promising and may be useful. It has some evidence to support it, but more evidence is needed to be sure it works.

 

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  • 3 smiliesThese treatments are very useful. They are strongly supported as effective by scientific evidence.
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  • 1 smileyThese treatments are promising and may be useful. They have some evidence to support them, but more evidence is needed to be sure they work.
  • No smiley On the available evidence, these treatments do not seem to be effective.
  • Question markThese treatments have not been properly researched. It is not possible to say whether they are useful or not.
  • Exclamation MarkSafety or other concerns have been raised for the use of these treatments.

What is it?

Omega-3 is a type of polyunsaturated fatty acid. Omega-3 fatty acids are important for overall health and wellbeing.

There are different types of omega-3 fatty acids. These are:

  • alpha-linolenic acid (ALA);
  • eicosapentaenoic acid (EPA); and
  • docosahexaenoic acid (DHA).

ALA is found mostly in walnuts, some seeds, and some oils. EPA and DHA are found in oily fish and eggs. ALA is converted into EPA and DHA by the body.

How does it work?

Omega-3 and depression have been linked in the following ways.

  • Some people with depression have lower levels of omega-3 in their red blood cells. This has led to the belief that low levels of omega-3 are linked with depression.
  • Some people believe depression is caused by inflammation. Omega-3 may reduce inflammation.
  • Countries with high fish consumption have lower reported rates of depression.

Is it effective?

While there have been a number of studies which have looked at the effectiveness of omega-3 for treating depression, many of these studies are of low quality. More research of better quality is needed.

Some meta-analyses (reviews of many studies) have found that omega-3 helped to reduce depression symptoms, particularly for people who are also taking anti-depressants. One review found that omega-3 only led to very small improvements in depression symptoms.

One meta-analysis of data from 35 trials found that supplements containing mostly EPA-type omega-3 were effective at reducing depression symptoms, but supplements containing mostly DHA-type omega-3 were no more effective than placebos (dummy treatments) at reducing depression symptoms.  

Are there any disadvantages?

There are some reported side effects of fish-oil tablets, including bloating, gas, belching, nausea, bad breath and/or loose stools.

Some supplements can be harmful or ineffective if you take the wrong dose. Talk to your health care professional if you are thinking of taking supplements, including omega-3.

Where do you get it?

Many foods are high in omega-3 fatty acids. These include oily fish (such as salmon, mackerel, and sardines), eggs, walnuts, some seeds (including hemp and flaxseed), and some oils.

Omega-3 supplements are available at supermarkets, health food shops and pharmacies.

Fish oil supplements may also contain omega-3 fatty acids but the amount will vary. It is important to check the label to see if the supplement contains omega-3.

Recommendation

There some is evidence to suggest omega-3 helps depression, but more studies of better quality are needed. Omega-3 appears to be more effective for people who are also taking anti-depressants, and some types of omega-3 may be more effective than others. 

Key references

  • Appleton KM, Sallis HM, Perry R, Ness AR, & Churchill R. Omega‐3 fatty acids for depression in adults. Cochrane Database of Systematic Reviews. 2015; 11.
  • Grosso G, Pajak A, Marventano S, Castellano S, Galvano F, Bucolo C, et al. Role of omega-3 fatty acids in the treatment of depressive disorders: A comprehensive meta-analysis of randomized clinical trials. PLoS One; 2014: e96905.
  • Hallahan B, Ryan T, et al. Efficacy of omega-3 highly unsaturated fatty acids in the treatment of depression. The British Journal of Psychiatry. 2016; 209(3), 192-201.
  • Mocking RJT, Harmsen I, et al. Meta-analysis and meta-regression of omega-3 polyunsaturated fatty acid supplementation for major depressive disorder. Translational psychiatry. 2016; 6(3), e756.

Last reviewed and updated: 1 May 2019

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