The link between omega-3 long-chain PUFA on depression in healthy subjects has been looked at intensely within the research community in recent years, but with most studies so far focused on populations eating Western diets with low fish intake it remains unclear whether there is such a link within populations where fish intake is high.
This latest Japanese study involving 1050 men and 1073 women with an average age of 60 sought to find this out.
Using blood samples collected early in the morning after at least 12 hours of fasting, they found serum concentrations of omega-3 but not omega-6 were inversely associated with depressive symptoms within this population.
There were no significant differences in any serum fatty acid concentrations between groups however there were marginally significant differences in several fatty acids between those with and without depressive symptoms, including EPA, omega-3 PUFA and omega-3 long chain PUFA.
Using the Centre for Epidemiologic Studies Depression Scale (CES-D), they found 266 subjects (12.5%) had depressive symptoms overall.
The World Health Organisation (WHO) predicts that depression will be one of the top three causes of disability-adjusted life years lost by 2030.
According to its seventeen nation World Mental Health Survey, about 5% of people report having experienced at least one episode of depression during their lifetime.
The WHO defines depression as a "common mental disorder, characterized by sadness, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, feelings of tiredness and poor concentration".
The average omega-3 long chain PUFA concentrations of subjects with and without depressive symptoms were 264.1 microgram (μg) per ml and 276.0 μg/ml, respectively.
"[T]he present study suggests that the serum levels of EPA and DHA may be associated with depressive symptoms in Japanese with higher blood levels of omega-3 LCPUFA. Therefore, even in countries with a higher fish intake, omega-3 LCPUFA intake in the usual diet may lower depressive symptoms. Furthermore, the efficacy of omega-3 LCPUFA against depressive symptoms may be present in Japanese community dwellers," they wrote in the British Journal of Nutrition.
The participants with depressive symptoms were also significantly more likely to be unmarried, have fewer years of education and a higher rate of past stroke compared with those without such symptoms.
The study was conducted by researchers from the Japanese National Centre for Geriatrics and Gerontology, the Aichi Shukutoku University and the Nagoya University of Arts and Sciences in Japan and the company Suntory Wellness Limited, which produces omega-3 supplements.
Despite a growing body of evidence, a Cochrane review last year pulled apart data from 26 randomised trials involving a total of 1,458 participants and concluded there was insufficient evidence to support the use of omega-3 supplements as a treatment for depression.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515004754
“Cross-sectional association between serum concentrations of n-3 long-chain PUFA and depressive symptoms: results in Japanese community dwellers”
Authors: C. Horikawa, R. Otsuka, Y. Katoa, Y. Nishita, C. Tange, S. Kakutania, T. Rogia, H. Kawashima, H. Shibata, F. Ando and H. Shimokata