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Fishing for answers

Is something fishy about fish oil? <i>Photo: Paul Jones.</i>

Is something fishy about fish oil? Photo: Paul Jones.

Despite its promise of helping to protect our hearts and minds, fish oil’s reputation has taken some hits lately. Omega-3 supplements don’t appear to improve cognitive function in older people, reported one study last year, while another review looking at prevention of heart disease and stroke concluded that fish oil wasn’t much help there, either.

But it’s not time to write off fish oil yet – at least not when it comes to mental health, says Professor Gordon Parker, Scientia Professor at the School of Psychiatry at the University of New South Wales.

The reason for conflicting findings may be that different formulations of fish oil supplements have different effects 

"Even though research into fish oil’s effects on depression has had mixed results, it’s an evolving story," says Parker who believes the reason for  conflicting findings may be that different formulations of fish oil supplements have different effects.

"We still need to work out which formulation is best for depression and at what dose," he says.

Fish oil contains omega 3 fats with names so eye-glazing that they’re best known by their initials. There’s EPA (eicosapentanoic acid) and DHA (docosahexaenoic acid) both of which help regulate the brain chemicals that affect our mood and cool the inflammation thought to contribute to depression, arthritis, heart disease and dementia.

To get enough of these fats we need fish – two to three serves of oily fish like sardines, salmon, trout or mackerel weekly delivers the daily 500mg of omega-3 fat recommended by the Heart Foundation. Although we can make some of these fats ourselves by eating plant foods like flaxseed, chia seeds and walnuts which contain another omega-3 fat - ALA, short for alpha linolenic acid - we only produce a small amount.       

For improving depression, fish oil supplements containing more EPA than DHA appear to be the most effective, but more studies are needed says Parker, the former director of the Black Dog Institute, which specialises in treating and researching mood disorders. Although finding the optimal dose for depression is a work in progress, the Institute generally recommends two 500mg capsules daily.  

"Fish oil may also help protect young people from serious mental illness – an Australian study of adolescents at risk of schizophrenia found that those taking fish oil supplements had a much lower risk of developing psychosis," he adds. "Although the general advice is two to three serves of oily fish each week, for adolescents and young people with an increased risk of psychosis or mood disorder, there’s an argument for taking three or four capsules daily of a fish oil supplement containing 180mg of EPA and 120mg of DHA."

Parker is working on a study* to see if fish oil helps women with bipolar disorder keep their moods stable   during pregnancy. Pregnant women with bipolar are between a rock and a hard place – using mood stabilising drugs is linked to an increased risk of pregnancy complications, but avoiding medication can seriously affect their mental health.

"We know that omega 3 supplements are safe in pregnancy and that they can help with depression in bipolar disorder when they’re used  in conjunction with medication – now we want to find out if omega-3 supplements alone can keep moods stable in pregnancy," says Parker.

Differences in the quality of fish oil supplements and the use of different doses can also explain mixed results in studies on cardiovascular disease, says Dr Rob Grenfell, the Heart Foundation’s Director of Cardiovascular Health.

"There’s a lot more to learn about fish oil, but research so far suggests it helps keep blood vessels healthy and reduces the risk of clots by helping thin the blood. It’s a long term benefit that comes from taking it consistently which is why we recommend sticking with oily fish three times a week,” he says. "If you can’t eat fish for some reason, ask your doctor about supplements."

Still, you can't have a conversation about eating fish without thinking about the sustainability issue. For information about shopping for sustainable seafood, see Australia's Sustainable Seafood Guide from the Australian Marine Conservation Society.

*Women who have bipolar disorder and are pregnant (less than 10 weeks) are invited to participate in this study which is recruiting both women who’ve decided to maintain their mood stabiliser medication and women who have decided to discontinue it and take fish oil. For more information, contact Amelia: or (02) 9382 9268.

19 comments so far

  • I was mildly (not clinically) depressed a couple of years ago when life took a downward turn. I began taking omega-3 supplements after becoming concerned about the omega-3/omega-6 imbalance I'd read about. I noticed, after a few months, that my general mood had lifted. My somewhat creaky knees also improved. I had not noticed this before when I was eating a 95g tin of tuna almost daily for lunch, so I presume either the tin isn't a big enough serve, or the canning process damages the omega-3.

    The sustainability issue does concern me (especially as my current supplement is derived from krill) so I ought to rejig my diet to include cooking fish more often, though overfishing is also a concern.

    Date and time
    January 30, 2013, 10:36AM
    • you can get mussel oil (Lyprinol) from Blackmores that is rich in fatty acids that comes from sustainable farming (as opposed to krill and fish oil)

      Date and time
      January 30, 2013, 1:38PM
    • Here's a link to Blackmore's sustainability policy

      Date and time
      January 30, 2013, 2:04PM
    • I am dubious as to the long term sustainability of any fish or krill from wild catches and think it preferably to choose a farmed alternative whenever it is available.

      Date and time
      January 30, 2013, 2:16PM
    • I'll look into the mussels. Farmed fish concern me because they are often fed on wild-caught fish, so all they've done is push the sustainability issue further up the chain. I won't eat farmed salmon for this reason, although the Tassal website says they are working on a vegetable meal for their fish to replace the.current one based on wild fish.

      Date and time
      January 30, 2013, 4:20PM
  • I take fish oil liquid daily as I have heard it is better (and fresher) than the capsule version. Is there any research to back this up?

    Date and time
    January 30, 2013, 11:42AM
    • Hi - I did a quick search and  although there's info on the net saying that the liquid is better absorbed I couldn't see any research. Maybe someone else can shed some light on this. 

      Date and time
      January 30, 2013, 12:01PM
    • Paula, there does not seem to be much in PubMed on this.

      The best that I can come up with is that it seems that there are large variations in the quality of fish oil capsules ( Similar variations have been reported for liquid fish oil products (

      Dr Kiwi
      Date and time
      January 30, 2013, 5:42PM
    • Thanks!

      Date and time
      January 30, 2013, 7:50PM
  • I could write a book about fish oil and the things that pharma companies love to deliberately overlook in studies.
    I will keep it simple by advising that a therapeutic dose of fish oil is 1g of EPA minimum. Any less, just do not bother. This is general knowledge among nutritionists and other natural health therapists. It is time the public were aware of this simple fact.

    Therapeutic dose
    Date and time
    January 30, 2013, 1:11PM

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