Omega-3 fatty acids are present in a variety of foods.
The fatty acids EPA and DHA are present mainly in fish such as salmon, herring, mackerel, anchovies, and sardines. These fatty acids, especially DHA, are probably important for brain function, and are also found in the retina of the eye.
Another omega-3 fatty acid, ALA, is present from plant sources such as canola oil, flax, and walnuts. ALA may be converted in the body to DHA.
There is some evidence that there are health benefits from diets higher in omega-3 fatty acids, or diets supplemented with extra omega-3.
Of interest for psychiatry, omega-3 supplementation may be a safe adjunct in the treatment of depression. Fish oil is probably the simplest source of extra EPA and DHA.
The only problem with increasing fish consumption is the exposure to environmental contaminants such as mercury and PCBs. Fish oil capsules may actually have less of these contaminants than pure fish, especially if the oil has been refined to remove contaminants. In any case, I think the benefit-risk ratio is very favourable, and that 1-3 capsules per day of fish oil is quite safe. And I feel confident to recommend increased fish intake in the diet. For vegetarians, increased intake of walnuts, canola, and flax could be recommended.
(a review of the studies over the past decade looking at omega-3 supplements in mood disorders)
(a nice review from The American Journal of Psychiatry in 2006, summarizing epidemiological data associating low fish consumption with higher rates of mood disorder, and summarizing some of the treatment studies showing antidepressant effects of omega-3 supplements in depression, bipolar disorder, and borderline personality)
(this is a recent study showing beneficial effects of omega-3 supplements in children with bipolar symptoms;but it was not a randomized or controlled study)
(this is a recent local study analyzing fish oil supplements for environmental pollutant levels, such as PCBs. Based on this study, one should avoid supplements of products such as seal or shark oils, which have much higher contaminant levels.)
(one of the articles summarizing evidence that omega-3 intake reduces the incidence or progression of macular degeneration, which is a common cause of visual loss in those over 65 years of age).
(a huge study, published in 2006, involving data from over
40 000 people over 18 years of follow-up--it shows a slight reduction in cardiac disease associated with higher fish consumption, but no change in overall "major chronic disease risk". But, incredibly, and unfortunately, they did not include mood or other psychiatric disorders in their assessment of "chronic disease" outcomes. Yet, studies of this type exemplify that The American Journal of Clinical Nutrition is an excellent journal, a valuable and practical source of evidence-based health information which could guide nutritional choices).