Cod liver oil linked to less depression

The study, published in the Journal of Affective Disorders , followed 21,835 subjects aged between 40 and 49 and 70 and 74 years, and found that the prevalence of depressive symptoms was 29 per cent lower in regular cod liver oil users than the rest of the population.

Numerous observational studies and uncontrolled trials have reported the benefits of fish oils and omega-3 fatty acids DHA and EPA on the behaviour and learning, especially in kids, as well for improving the symptoms of depression.

"In this large population based cross-sectional study we found that daily use of cod liver oil was negatively associated with high levels of depressive symptoms and that the prevalence of such depressive symptoms decreased with the duration of cod liver oil use," wrote lead author Maria Baroy Raeder from Haukeland University Hospital Baroy Raeder and co-workers used data from the population based cross-sectional health survey "The Hordaland Health Study '97-'99" (HUSK), and report that 8.9 per cent of subjects used cod liver oil daily.

"The users of cod liver oil were significantly less likely to have depressive symptoms than non-users after adjusting for multiple possible confounding factors (29 per cent reduction)," wrote the researchers.

They also report that length of regular cod liver oil supplementation was found to influence the prevalence of high levels of depressive symptoms - the longer the duration of supplementation, the lower the prevalence of symptoms of depression.

The study does have several limitations, most notably the lack of dietary data that could have affected the results.

In addition, socio-economic factors were not accounted for in the study, which also may affect the overall health and mental state of the subjects.

The researchers, therefore, stressed that the results should be interpreted with care.

"To confirm such a possible protective effect, randomized controlled trials are needed," concluded the researchers.

Commenting independently on the research, Professor David Kendall from the University of Nottingham told the BBC that since fish oil appears to improve cardiovascular health, it was not surprising that healthier people may suffer less from symptoms of depression.

Kendall added that fish oil could directly impact upon depression, but echoed the notes of caution by the researchers in the interpretation of the results.

Omega-3 are polyunsaturated fatty acids (PUFAs) consumed predominantly in the diet from fish, nuts and seeds.

The fish oil PUFAs include Eicosapentaenoic acid (EPA) and Docosahexaenioc acid (DHA).

EPA is proposed to function by increasing blood flow in the body.

It is also suggested to affect hormones and the immune system, both of which have a direct effect on brain function.

DHA, on the other hand, is involved in the membrane of ion channels in the brain, making it easier for them to change shape and transit electrical signals.

Source: Journal of Affective Disorders August 2007, Volume 101, Issues 1-3, Pages 245-249 "Associations between cod liver oil use and symptoms of depression: The Hordaland Health Study" Authors: M. Baroy Raeder, V.M. Steen, S. Emil Vollset and I. Bjelland