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omega 3 fish oil

Complimentary / alternative medicine

Omega 3 is found in a range of products available from pharmacies, health food shops and supermarkets.

It comes in two main forms:

   (i) Highly unsaturated omega 3 fatty acids, which include eicosopentaenoic acid (EPA) and docosahexaeioc acid (DHA)

   (ii) Less highly unsaturated omega 3 fatty acids, usually from vegetarian sources such as flax seed oil

Omega 3 has been investigated in the treatment of depression, bipolar disorder and schizophrenia. There is no conclusive evidence that it is an effective treatment on its own. Sometimes it might be helpful in addition to other treatments.

There is some debate about the dose of omega 3 that should be used in psychiatric illness. The consensus appears to be that an appropriate dose is between 1-3 grams per day of EHA + DHA.

Quality of preparation is important because of the potential for mercury poisoning in concentrated fish oil.




•    Some studies have suggested that there is an inverse relationship between rates of depression and fish consumption (1,2), although this is not a consistent finding, with a recently conducted large cohort study unable to demonstrate such an association. (3)
•    The studies that have been conducted investigating the role of omega 3 fish oils in the treatment of depression are of variable design quality.
•    A meta-analysis (4) of 35 such studies concluded that there is possibly some benefit of adding omega three to existing antidepressant treatment, with a small number of trials indicating benefit, but because of the heterogeneity of the studies, with many studies unable to demonstrate any benefit, larger, well conducted studies are needed to further investigate the role of omega 3 in the treatment of depression (4, 5).
•    There is no evidence for omega 3 fish oil as a standalone treatment for depression.


Bipolar disorder


•    The quality of studies investigating omega 3 fish oils in bipolar disorder is highly variable with many trials being of poor quality design and there is a need for large, well conducted studies. (6)
•    One well designed study has demonstrated that there was a better response in patients with bipolar depression who had omega 3 added to their psychiatric medication. (7)
•    No trials have demonstrated effectiveness of omega 3 in bipolar mania.
•    There is no evidence for omega 3 fish oil as a standalone treatment for bipolar disorder.




•    There have been a number of trials that have investigated the use of omega 3 in the treatment of schizophrenia, with mixed results. (8)
•    A Meta analysis of these trials concluded that the available data was inconclusive and that further research using large, well designed, controlled and reported trials is needed.


Use in Pregnancy


•    A recent meta analysis indicated that the use of omega 3 during low risk pregnancies is associated with small increases in the duration of pregnancy and infant head circumference, compared to women who do not take them .(9)
•    There are no significant differences in rates of preeclampsia, caesarean sections, gestational diabetes, infant birth weight or placental birth weight between women using omega 3 during pregnancy compared to controls. (9)
•    Overall the data available on the safety of omega 3 during pregnancy is reassuring
•    Data on the side effects of omega 3 is limited but several studies report a higher incidence of mild gastrointestinal effects in pregnant women  using omega 3, including heartburn and bad breath.
•    It may be safer to increase omega 3 levels during pregnancy through use of dietary supplements rather than increased fish intake because of the risk of increased exposure to contaminants. (5)


Use in Lactation


•    There is a significant lack of studies designed to investigate the safety of omega 3 supplementation  in breast-feeding (10)
•    Levels of DHA are significantly higher in the breast milk of mothers who have a high dietary intake of omega 3 DHA (including using supplements).  (11)


1. Tanskanen A, Hibbeln JR, Hintikka J, Haatainen K, Honkalampi K, Viinamaki H. Fish consumption, depression, and suicidality in a general population. Arch Gen Psychiatry 2001;58:512–3.
2. Hibbeln JR. Seafood consumption, the DHA content of mothers’ milk and prevalence rates of postpartum depression: a cross-national, ecological analysis. J Affect Disord 2002;69:15–29.
3. STRØM ET AL. Fish and long-chain n23 polyunsaturated fatty acid intakes during pregnancy and risk of postpartum depression: a prospective study based on a large national birth cohort. Am J Clin Nutr 2009;90:149–55
4. APPLETON ET AL. Updated systematic review and meta-analysis of the effects of n23long-chain polyunsaturated fatty acids on depressed mood Am J Clin Nutr 2010;91:757–70.
5. A-M. REES, M-P. AUSTIN, G.B. PARKER. Omega-3 fatty acids as a treatment for perinataldepression: randomized double-blind placebo-controlled trial Australian and New Zealand Journal of Psychiatry 2008; 42:199_205
6. Montgomery P, Richardson AJ. Omega-3 fatty acids for bipolar disorder. Cochrane Database of Systematic Reviews 2008, Issue 2. Art. No.: CD005169. DOI: 10.1002/14651858.CD005169.pub2.
7. Frangou S, Lewis M, McCrone P. Efficacy of ethyl-eicosapentaenoic acid in bipolar depression: randomised double-blind placebocontrolled study. British Journal of Psychiatry 2006;75(4-5):315–21.
8. Irving CB, Mumby-Croft R, Joy LA. Polyunsaturated fatty acid supplementation for schizophrenia. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD001257. DOI:10.1002/14651858. CD001257.pub29.
9.Szajewska et al. Effect of n–3 long-chain polyunsaturated fatty acid supplementation of women with low-risk pregnancies on pregnancy outcomes and growth measures at birth: a meta-analysis of randomized controlled trials. Am J Clin Nutr 2006;83:1337-44
10. Lewin GA, Schachter HM, Yuen D, Merchant P, Mamaladze V, Tsertsvadze A, et al. Effects of Omega-3 Fatty Acids on Child and Maternal Health. Evidence Report/Technology Assessment No. 118. (Prepared by the University of Ottawa Evidence-based Practice Center, under Contract No. 290-02-0021.) AHRQ Publication No. 05-E025-2. Rockville, MD: Agency for Healthcare Research and Quality. August 2005.
11. Dunstan JA, Roper J, Mitoulas L, Hartmann PE, Simmer K, Prescott SL The effect of supplementation with fish oil during pregnancy on breast milk immunoglobulin A, soluble CD14, cytokine levels and fatty acid composition. Clin Exp Allergy. 2004 Aug;34(8):1237-42.





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